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Veterinary Pharmacology > Midterm II - Topic 19,20,21 > Flashcards

Midterm II - Topic 19,20,21 Flashcards

19: PHARMACOLOGY OF THE AUTONOMIC NERVOUS SYSTEM: 20: PARASYMPATHETIC NERVOUS SYSTEM: 21: SYMPATHETIC NERVOUS SYSTEM

1
Q

19: PHARMACOLOGY OF THE AUTONOMIC NERVOUS SYSTEM:

  • SYMPATHETIC NERVOUS SYSTEM
A
  • “Fight or flight”.
  • Reaction of the body to emergency situations,
  • short-term stress.
  • Operating adrenaline and noradrenaline.
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2
Q

19: PHARMACOLOGY OF THE AUTONOMIC NERVOUS SYSTEM:
* Parasympathetic nervous system:

A
  • “Rest and digest”.
  • Regaining health, energy, and nutritional supplies.
  • The neurotransmitter will be acetylcholine.
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3
Q

Synthesis of catecholamines:

A

PRECURSOR = Phenylalanine

L-DOPA = decarboxylated to form Dopamine.

–> This will form Noradrenaline via beta hydroxylation

–> With the transferring of a methyl group,

= forms Adrenaline

(the difference between the two being that noradrenaline is lacking a methyl group).

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4
Q

Synthesis of Acetylcholine:

A

CONTAINS= quaternary nitrogen + acetate group.

NEED = choline

= Taken up from the synaptic cleft and the acetyl group donor also.

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5
Q

What kind of function will be influenced by the parasympathetic and sympathetic nervous system?

  • PARASYMPATHETIC NERVOUS SYSTEM
A

If the parasympathetic nervous system/parasympathomimetic is stimulated because it is rest and digest,

  • More secretion e.g. gastric, intestinal fluid etc.
  • Bowel movement
  • constriction of the pupils.
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6
Q

What kind of function will be influenced by the parasympathetic and sympathetic nervous system?

  • SYMPATHETIC NERVOUS SYSTEM
A

Sympathetic nervous system stimulated = almost opposite effect.

  • The heart will pump faster (positive chronotropic effect),
  • dilation of the pupils,
  • lower gastric secretion,
  • bowel movement will be limited because you would like to fight.
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7
Q

Parasympathetiic nervous system use…?

A

CHOLINERGIC TRANSMITTERS

= ACETYL CHOLINE

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8
Q

Sympathetiic nervous system use…?

A

NORADRENALINE TRANSMITTERS

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9
Q

Peripheral nervous system:

Can be broken up into?

A
  1. Somatic nervous system,
  2. Sympathetic nervous system, and
  3. Parasympathetic nervous system.
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10
Q

Parasympathetic and sympathetic nervous system:

How does it act?

A
  1. Pre-ganglion - Transmits Acetylcholine(PS+S nervous system)
  2. Post-ganglion
  • ​Release NORADRENALINE - SYMPATHETIC NS
  • Release ACETYL CHOLINE - PARASYMPATHETIS NS

Acetylcholine - binds to nicotinic acetylcholine receptors however, these two systems will differ because (postganglion)

The noradrenalin will bind to different receptors:

  • alpha-1,
  • alpha-2,
  • beta-1, or
  • beta-2 receptors.

The acetylcholine (PS) will bind to Muscarine receptors (postganglionic neurons)

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11
Q

The target organs of the Parasympethetic and sympathetic nervous systems?

A
  1. Smooth muscle,
  2. glands
  3. cardiac muscle.
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12
Q

PERIPHERAL NERVOUS SYSTEM

  • Somatic nervous system:
A
  • Non-depolarising muscle relaxants =
  1. ATRACURIUM,
  2. PANCURONIUM,
  3. VECURONIUM,
  4. ROCURONIUM etc.
  • Mechanisms of action = competitive antagonists of nicotinic acetylcholine receptors.
  • NO pre-ganglia or ganglion, there is only a post-ganglion which will release acetylcholine.
  • The target organ of this nervous system is skeletal muscle.
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13
Q

Somatic Nervous system

Mechanism of action

A

Competitive antagonists of nicotinic acetylcholine receptors.

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14
Q

Somatic nervous system

Ganglions??

A

NO pre-ganglia or ganglion,

Only post-ganglion - Release ACETYLCHOLINE.

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15
Q

Somatic Nervous system

Target organs

A

Skeletal muscle.

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16
Q

If you apply the non-depolarising muscle relaxant Curare (Indian poison), can you influence the Parasympathetic nervous system?

  • Why?
A

It will not have any effect on this nervous system.

There are nicotinic receptors but there is a difference in the subunits.

That is why if you add Curare to the NS, the parasympathetic nervous system will not be able to stop it.

You cannot influence this nervous system based on the different subunits. Nicotinic acetylcholine receptor is a Na+ channel so if the sodium is transported into the cell, depolarisation will occur.

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17
Q

What kind of receptor is Muscarinic acetylcholine receptors

A

G-protein-coupled receptors.

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18
Q

How does the G-Protein cascade get activated?

A

Ach binds to the Ach receptors and the G-protein cascade is activated.

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19
Q

How many different Muscarine acetyl subtypes(receprors) exist?

Which can we influence pharmacologically?

A

5 different subtypes (receptors).

Pharmacologically, we can mainly influence:

  • M1
  • M2
  • M3
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20
Q

What is this?

Fill in blanc spaces

A

This is a signalling cascade

A = Acetylcholine

B= Muscarinic Acetylcholine Receptor

C = G-Protein

1= ADENYL CYCLASE

2= PHOSPHOLIPASE C

3= K+ Channels

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21
Q

In which different organs can we find muscarinic receptors?

M1, M2 and M3

A

M2 in the heart

M1 and M3 in the EYE and many glands and have a connection with VASODILATION

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22
Q

Is the blood vessels innervated by the parasympathetic NS?

How does it achieve vasodilation?

A
  1. NOT innervated by the parasympathetic nervous system
  2. Vasodilation can be achieved via NO (nitrogen oxide).
  • NO will dilate the vessels rather than the PS nerve ending.
  • This is different in the sympathetic nervous system which does innervate the blood vessels.
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23
Q

What does “SLUDGE” stand for?

A

“SLUDGE” =

  • salivation,
  • lacrimation,
  • urination,
  • digestion,
  • gastro-intestinal upset and pain, and
  • emesis.
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24
Q

If you stimulate muscarinic receptors (PS NS) what will be the result?

A
  1. Bradycardia (negative chronotropic effect i.e. slow down the heart).
  2. Bronchoconstriction – cannot therapeutically be used.
  3. Miosis – can therapeutically be used in cases of glaucoma.
  4. Salivation
  5. Vomiting, diarrhea – can therapeutically be used for bowel atony..
  6. Urination – can therapeutically be used for urinary bladder atony.

i.e. we would consider stimulating the parasympathetic nervous system in some cases of treatment.

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25
Q

Drugs acting on the parasympathetic nervous system:

A

A. Parasympathomimetics: stimulate the parasympathetic nervous system: cholinergic drug =

  • acetylcholine,
  • parasympathetic stimulants,
  • acetylcholine receptor agonists.
  1. Direct Parasympathomimetics
  2. Indirect Parasympathomimetics

B. Parasympatholytics:

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26
Q

Drugs acting on the parasympathetic nervous system:

  • Pharmacological Effects:
A
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27
Q

Parasympathomimetics

  • Pharmacological Effects:
    1. ​EYE
A
  • The pupil will be constricted by reducing the intraocular pressure which can be useful in cases of glaucoma.
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28
Q

Parasympathomimetics

Pharmacological Effects:

​EYE

In case of KSC - Dry eye disease

A
  • In keratoconjunctivitis sicca (KCS = dry eye disease i.e. it is an auto-immune disease)
  • Lacrimal gland cannot produce enough fluid,
  • Apply parasympathomimetics, you can moisturize the eye by increasing lacrimal secretion
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29
Q

Parasympathomimetics

Pharmacological Effects:

​EYE

Problems when treating KCS

A

Auto-immune disease = symptomatic treatment rather than preventative treatment.

If you want to treat KCS, you can diagnose it via the Schirmer test which measures the amount of fluid secreted in the eye.

When it is a low amount = KCS (usually associated with dogs).

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30
Q

What should you treat KCS with?

A
  • In cases of KCS, you can try and add ointments,
  • Mainly administer immunosuppressants e.g. glucocorticoids (corneal laceration present or not?),
  • CYCLOSPORINE,
  • TACROLIMUS, because again, it is an auto-immune disease.
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31
Q

Parasympathomimetics

Pharmacological effect

Heart

A
  • Negative chronotropic effect (slow down the heart). Therapeutically, this will not be made use of.
  • There are no inotropic effects – parasympathomimetic drugs do not influence the level of contractions of the heart.
  • Vasodilation via NO - nitrogen monoxide (rather than parasympathetic innervation).
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32
Q

Parasympathomimetics

Pharmacological effects

GI- Tract

A
  • Secretion enhanced
  • Peristalsis and the Bowel movement will be increased
    • i.e. smooth muscle contraction.
  • Vomiting
  • Diarrhea
  • Glandular hyperfunction
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33
Q

Parasympathomimetics

Pharmacological effects

Respiratory Tract:

A
  1. Bronchoconstriction
  2. increased bronchial secretion

= parasympathomimetics are completely contraindicated in asthmatic cases.

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34
Q

Parasympathomimetics

Pharmacological effects

Urinary Tract:

A

Useful if you would like to relax the sphincter and constrict the bladder to allow for urination.

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35
Q

Parasympathomimetics

What is Direct parasympathomimetics:

A

These will directly stimulate the ACh-receptors.

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36
Q

Parasympathomimetics

What are the different drugs used for direct parasympathomimetic

A
  1. Acetylcholine:
  2. Carbachol:
  3. Bethanechol:
  4. Methacholine:
  5. Pilocarpine:
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37
Q

Direct parasympathomimetics:

USAGE OF ACETYLCHOLINE

A

Acetylcholine:

  • Therapeutically, this cannot be used = very short half-life!
  • It is non-specific and non-selective.
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38
Q

Direct parasympathomimetics:

USAGE OF CARBACHOL

A

Carbachol:

  • It is old and obsolete.
  • Used to treat glaucoma - eye drops.
  • Applied in the uterus = remove content in the case of metritis (intrauterine tablet).
  • It is non-specific to M-ACh receptors
  • Several side effects.
  • It used to be used as a laxative in pigs - emesis.
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39
Q

Direct parasympathomimetics:

USAGE OF BETHANECHOL

A

Bethanechol: (Human).

  • M-ACh-specific i.e. it has less side effects.
  • Causes the induction of intestinal peristalsis after operations.
  • Useful in urinary bladder atony (veterinary use also).
    • Spinal trauma = sometimes the urinary bladder cannot function appropriately = Bethanechol= induce urination.
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40
Q

Direct parasympathomimetics:

USAGE OF METHACHOLINE

A

Methacholine: (Human).

  • Theoretical indication & Practical indication.
  • M-ACh-specific.
  • Theoretically = cardiovascular system for atrial fibrillation
  • Practically it is NOT
  • Useful in ergot-toxicosis—> gangrene blood vessels
    • i.e. serious vasoconstriction.
      • Methacholine helps by causing vasodilation.
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41
Q

Direct parasympathomimetics:

USAGE OF PILOCARPINE

A

Pilocarpine:

  • Natural alkaloid.
  • Used in glaucoma
    • (miosis can be seen approx. 15 minutes later which lowers the intraocular pressure)
  • KCS
    • (increasing the amount of tears from the lacrimal gland).
    • Improves salivation mildly.
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42
Q

Parasympathomimetics

What is Indirect parasympathomimetics:

A
  • Inhibit the ACh-esterase enzyme = lowers the degradation of ACh
    • ​i.e. increases the amount of ACh.
  • Various N-ACh and M-ACh effects & side effects.
    • Primarily on the nicotinic-ACh receptors and
    • furthermore on the muscarinic-ACh receptors and,
    • also on the ACh receptors in the CNS.
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43
Q

INDIRECT PARASYMPATHOMIMETICS

Where can the blockage happen?

A

The blockage can happen as serine residues.

You can find serine in the ACh-esterase which contains a hydroxyl group.

These agents can block the ACh-esterase because they will esterify the serine OH group.

This means that ACh-esterase will not be available towards ACh binding. These are reversible, this means that it can be controlled i.e. regulated.

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44
Q

INDIRECT PARASYMPATHOMIMETICS

What will happen to the blockage if you add ORGANOPHOSPHATES

A
  • Bind to ACh-esterase for a longer period.
    • NOT GOOD
      • Excessive cholinergic sign of tremors and convulsions.
      • This depends on the severity of the organophosphate-toxicosis.
  • 1st sign of this toxicosis—> binding to ACh-esterases= >
    • Increase in ACh = PARASYMPATHOMIMETIC EFFECT
      • Salivation,
      • Diarrhoea,
      • Vomiting,
      • if severe,
        • tremors,
        • convulsions,
        • Seizures –> Increase in temperature –> Death.
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45
Q

INDIRECT PARASYMPATHOMIMETICS

Why would we apply organophosphates?

A

It can be used against:

  1. parasite infestation
  2. ectoparasites
  3. insecticides
46
Q

PARASYMPATHOMIMETICS

What are the INDIRECT PARASYMPATHOMIMETIC drugs

A
  1. Physostigmine:
  2. Neostigmine:
  3. Pyridostigmine
  4. Edrophonium: TENSILON
  5. Organophosphates:
47
Q

INDIRECT PARASYMPATHOMIMETICS

PHYSOSTIGMINE in general

A

Physostigmine:

  • Lipophilic molecule with a Tertiary nitrogen structure
  • Causes hallucination.
  • Systematically, we require a quaternary nitrogen structure.
    • This is useful in the form of eye drops i.e. locally and topically but NOT systematically.
  • ​Used to treat glaucoma,
    • However, it has a tolerance
      • ie. when you apply the drug, there will be a certain biological effect.
      • After a while, you have to increase the dose to have that same biological effect/response.
  • Very fast = TACHYPHYLAXIS.
  • Very small therapeutic index systematically
    • ​but is used in ATROPINE POISONING
      • Atropine is a parasympatholytic which crosses the blood-brain barrier i.e. for treatment, we need a parasympathomimetic that also crosses the blood-brain barrier – Physostigmine.
48
Q

INDIRECT PARASYMPATHOMIMETICS

*NEOSTIGMINE in general*

A

NEOSTIGMINE:

  • This structure has quaternary nitrogen
    • = good –> not cross the blood-brain barrier
      • i.e. it is not as lipophilic.
  • It can be used systematically = Because NO effect on the CNS.
  • Useful as eye drops
    • Safer systematically (injected IV or IM)
      • Very low oral absorption.
  • The therapeutic indication = MYASTHENIA GRAVIS
    • An auto-immune disease = antibodies against the ACh receptors = causes paralysis of all muscles.
    • This is very difficult to treat, even symptomatically.
    • Due to the myasthenia gravis,
      • ACh receptor will be damaged
      • = lower chance of the Neostigmine to bind.
  • Suspends the action of nondepolarizing muscle relaxants
    • because they are competitive antagonists of the receptor,
    • Administering parasympathomimetic restores the function of the skeletal muscle
  • Increases intestinal motility
  • Induces emesis.
49
Q

INDIRECT PARASYMPATHOMIMETICS

PYRIDOSTIGMINE in general

A

PYRIDOSTIGMINE

  • Quaternary nitrogen structure,
    • making it less lipophilic.
  • Advantage over Neostigmine
    • You can apply it orally.
  • It is the first drug that can be applied systematically and orally.
  • Best bioavailability (3-8%).
  • Lasts for a longer period
  • Used to treat MYASTHENIA GRAVIS
  • Increases intestinal motility.
50
Q

INDIRECT PARASYMPATHOMIMETICS

EDROPHONIUM in general

A

Edrophonium: TENSILON

  • Difference between edrophonium & pyridostigmine/neostigmine
    • is that this one will have a short action
    • i.e. you cannot treat MYASTHENIA GRAVIS
    • Only useful to test the patient
      • ​because if it is applied, the effect will only last for 15 minutes and after that time, the patient will worsen.
    • Not used to treat the patient but to DIAGNOSE it (Tensilon-test).
    • It causes inhibition in the neuromuscular junction.
      • This action is suspended by diffusion (5-15 minutes).
51
Q

INDIRECT PARASYMPATHOMIMETICS

ORGANOPHOSPHATE in general

A

Organophosphates:

  • Irreversible inhibition of AChE.
  • Good to use as an ectoparasiticide (e.g. diazinon).
  • It is very difficult to treat organophosphate toxicosis
    • But ATROPINE and PRALIDOXIME (parasympatholytics) can help.
  • ECHOTHIOPATE = Organophosphate used in human therapy to treat GLAUCOMA but only as eye drops.
  • ATROPINE has a very narrow therapeutic index, and its dosage is 0.01-0.02 mg/kg however, when treating organophosphate toxicosis = You can administer 0.1mg/kg.
    • If the dose is administered in other cases= Can kill the animal.
  • PRALIDOXIME is an AChE activator (another example of this is OBIDOXIME).
    • Be careful when administering this drug as
      • You must be within hours of the toxicosis!!
      • If you wait a day, it will not work.
52
Q

PARASYMPATHETIC NERVOUS SYSTEM

Parasympatholytics:

A

Parasympatholytics:

  • Anticholinergic drugs (muscarinic-receptor antagonists).
    1. Atropine:
  • Tropane-alkaloid. On the WHO essential drug list.
    1. Datura stramonium,
    2. Atropa belladonna,
    3. Hyoscyamus niger.
53
Q

PARASYMPATHETIC NERVOUS SYSTEM

PARASYMPATHOLYTICS

A
54
Q

PARASYMPATHIC NERVOUS SYSTEM

PARASYMPATHOLYTICS

Pharmacological effects

EYE

A

Eye:

  • Cycloplegia is the paralysis of the ciliary muscle of the eye
    • Causes lack of accommodation/accommodation disturbances.
    • Causes the ciliary body to spasm and cause pain.
  • Atropine helps to get rid of that pain by
    • Alleviating the spasms of the ciliary muscle.
    • It helps in inner eye inflammation
      • Only a symptomatic treatment rather than a causative treatment.
    • Atropine and its derivative causes mydriasis
      • which causes the pupil to dilate
        • ​Via the inhibition of the m. constrictor pupillae
        • And stimulation of the m. dilator pupillae.
    • Dilation of the pupil causes light sensitivity.
    • It is NOT used in cases of GLAUCOMA.
    • Dilating the pupil can be useful for eye examinations
      • ​however, we would NOT use ATROPINE for this
        • It has a very long-lasting effect on the healthy eye (a shorter-lasting effect on damaged eyes).
    • Instead, we use TROPICAMIDE or HOMATROPINE (atropine derivatives) as they have a shorter half-life.
  • It can also prevent the development of SYNECHIAE.
    • This is an accumulation of fibrin in the eye,
      • Causing the iris to connect to
        • either the cornea (anterior synechiae)
        • or to the lens (posterior synechiae).
      • You cannot stop the fibrin but by dilating the pupil, we shorten the connection of the iris, breaking the binding to either the cornea or the lens.
55
Q

PARASYMPATHIC NERVOUS SYSTEM

PARASYMPATHOLYTICS

Pharmacological effects

HEART

A

Heart: (cardiovascular system).

  • Causes tachycardia (acceleration of the heart)
    • by lifting the cholinergic blockade of the heart (n. vagus).
    • This is an effect we can make use of e.g.
      • in pre-medication.
  • It is not necessary but sometimes atropine can be used however, GLYCOPYRROLATE is better.
56
Q

PARASYMPATHIC NERVOUS SYSTEM

PARASYMPATHOLYTICS

Pharmacological effects

BRONCHI

A

Bronchi:

  • Bronchodilation (relaxing bronchial smooth muscle) and
  • Decreased mucus secretion,
    • this is what makes it a good pre-medication for surgeries.
57
Q

PARASYMPATHIC NERVOUS SYSTEM

PARASYMPATHOLYTICS

Pharmacological effects

GI-TRACT

A

GI Tract:

  • It will decrease the gastric secretion and salivation.
  • This is good for pre-medication for surgeries.
  • The transit time increases,
  • Causes constipation.
  • Stomach-acid decreases in small doses.
58
Q

PARASYMPATHETIC NERVOUS SYSTEM

PARASYMPATHOLYTICS

Therapeutic indications:

A
  • SHORT ACTING atropine derivatives (homatropine, tropicamide)
    • for diagnostic purposes
      • e.g. eye examinations.
  • LONG ACTING atropine
    • for the prevention of SYNECHIAE.
59
Q

PARASYMPATHETIC NERVOUS SYSTEM

PARASYMPATHOLYTICS

Premedication

A

Premedication:

  • We have to pre-medicate with parasympatholytics:
    1. as we would like to decrease secretion.
    2. The other purpose is that, when we have an anesthetic e.g. Fentanyl, the heart will slow down (bradycardia).
    • The parasympatholytics help to accelerate the heart (tachycardia).
    • When considering this, you must be aware of the agent that has been administered in connection with the anesthesia
      • ​e.g. if you have applied an alpha-2 agonist with the anesthesia, vasoconstriction will occur and if this is present together with tachycardia,
        • = exhaustion of the heart.
    • If you would like to antagonize bradycardia, you must be aware of whether or not vasoconstriction is present.

​​The solution to this is that we ONLY use parasympatholytics as a premedication if there is severe bradycardia on the heart.

60
Q

PARASYMPATHETIC NERVOUS SYSTEM

PARASYMPATHOLYTICS

Atropine VS Glycopyrrolate:

A

Atropine Vs Glycopyrrolate:

CARDIOVASCULAR EFFECT

  • If you apply atropine,
    • The cardiovascular effect will last for 20-30 minutes,
  • If you apply glycopyrrolate,
    • The cardiovascular effect will last for 2-3 minutes.

BOWEL ACTIVITY

  • If you apply atropine, it will just minimize the bowel activity for 1.5 hours
  • Glycopyrrolate will inhibit bowel activity for up to 7 hours.
    • ​Because of these issues, we would NOT like to administer glycopyrrolate to HORSES as it will cause COLIC.

SAFETY

  • Glycopyrrolate is much safer when considering cardiovascular issues and also CNS effects as it does not cross the blood-brain barrier whereas atropine does.
61
Q

PARASYMPATHETIC NERVOUS SYSTEM

PARASYMPATHOLYTICS

Bronchodilation:

A

Bronchodilation:

  • This can be applicable in cases of asthma which we can see frequently in cats.
  • In horses, asthma is called RAO (recurrent airway obstruction) = COPD (chronic obstructive pulmonary disease).
  • It is seen less frequently in dogs as canine chronic bronchitis
  • Asthma in humans.

IPATROPINE is better to use in these cases than atropine

  • Because it has a quaternary nitrogen structure,
  • = means that it cannot cross the blood-brain barrier.
  • It is in an inhalation form.
62
Q

PARASYMPATHETIC NERVOUS SYSTEM

PARASYMPATHOLYTICS

Antidiarrheals:

A

Antidiarrheals:

  • It will decrease secretion and bowel movement
    • i.e. atropine is used for obstipation,
      • meaning it is useful in cases of diarrhea.
  • It inhibits peristalsis and segmental contractions.
  • The recommendation is BENZETHIMIDE
    • as in ruminants, it will block bowel motility and stop the secretion at the same time.
  • Morphine derivatives in connection with diarrhea
    • They will influence the longitudinal movements (peristalsis).
  • It will not have a negative effect on segmental contraction.
  • This is good and is why we use morphine derivatives instead of atropine.
63
Q

PARASYMPATHETIC NERVOUS SYSTEM

PARASYMPATHOLYTICS

Antispasmodics:

A

Antispasmodics:

  • Parasympatholytics are useful in spasms,
    • especially BUSCOPAN (BUTYL-SCOPOLAMINE).
    • This is very effective in the intestine
      • used in cases of colic in horses.
64
Q

PARASYMPATHETIC NERVOUS SYSTEM

PARASYMPATHOLYTICS

Parkinson-disease:

A

Parkinson-disease:

  • In Parkinson’s, the
    • Dopamine levels are very low and the
    • ACh is very high.
  • The first-line treatment is to administer dopamine derivatives
    • e.g. LEVODOPA
      • (not dopamine itself as it will immediately be decomposed).
    • Levodopa will not be decomposed by decarboxylase
    • It is able to reach the brain.
    • This is only a substitution therapy because we are substituting dopamine.
    • The problem is that the dopamine-producing nerves are depleted.
  • If you see the symptoms of Parkinson’s,
    • it usually means that 90% of the neurons are obsolete already.
    • Parkinson’s patients have hypersalivation, and parasympatholytics are useful for this issue.
65
Q
A
66
Q

PARASYMPATHETIC NERVOUS SYSTEM

PARASYMPATHOLYTICS

Toxicity

A

Toxicity:

  • This drugs has a very low therapeutic index,
    • meaning it is very toxic.
    • It is very easy to overdose on it.
  • In rabbits, we do not see as much of sensitivity to atropine.
    • Enzyme atropine can be found in the rabbit’s body.
  • Horses are extremely sensitive to atropine.
67
Q

Summary

PARASYMPATHOLYTIC DRUGS

A
  1. Atropine:
  2. Glycopyrrolate:
  3. Homatropine:
  4. Tropicamide:
  5. Ipratropium:
  6. Benzetimide:
  7. Butyl-scopolamine:
68
Q

SUMMARY

PARASYMPATHOLYTIC DRUGS

Atropine:

A
  • The main drug,
  • highly toxic,
  • can cross the BBB.
  • Used in organophosphate toxicosis,
  • uveitis (synechiae),
  • asthma.
69
Q

SUMMARY

PARASYMPATHOLYTIC DRUGS

Glycopyrrolate:

A
  • Not in Hungary,
  • very low BBB-penetration,
  • used in premedication,
  • not used in eye examinations.
70
Q

SUMMARY

PARASYMPATHOLYTIC DRUGS

Homatropine:

A

Diagnostic eye examination.

71
Q

SUMMARY

PARASYMPATHOLYTIC DRUGS

Tropicamide:

A

Diagnostic eye examination.

72
Q

SUMMARY

PARASYMPATHOLYTIC DRUGS

Ipratropium:

A
  • Safe,
  • very low BBB-penetration.
  • COPD,
  • asthma.
73
Q

SUMMARY

PARASYMPATHOLYTIC DRUGS

Benzetimide:

A
  • anti-diarrheal
  • but morphine derivatives are better.
74
Q

SUMMARY

PARASYMPATHOLYTIC DRUGS

Butyl-scopolamine:

A

Used in horses with colic.

75
Q

SYMPATHETIC NERVOUS SYSTEM:

A

The neurotransmitter released from

  • Alpha preganglionic neurons of SNS = ACETYLCHOLINE
  • Postganglionic neurons = Release NORADRENALINE.
76
Q

SYMPATHETIC NERVOUS SYSTEM:

Postganglionic site

Which receptors are involved

A
  • ɑ1-receptors
  • ɑ2-receptors
  • β1-receptors
  • β2-receptors
  • β3-receptors
77
Q

SYMPATHETIC NERVOUS SYSTEM:

Postganglionic site

ɑ1-receptors:

A

ɑ1-receptors:

  • When stimulated, they cause vasoconstriction.
  • If you would like to reduce the blood pressure,
    • we would use alpha-1-antagonists to do so,
    • this is a therapeutic/practical use
    • i.e. alpha-1-blockers are anti-hypertensive.
  • Stimulation will also cause pupil dilation but therapeutically, this is not made use of.
    • Pupil dilation is just a side effect of their use.
78
Q

SYMPATHETIC NERVOUS SYSTEM:

Postganglionic site

ɑ2-receptors:

A

ɑ2-receptors:

Alpha-2-agonists e.g.

  1. XYLAZINE,
  2. DETOMIDINE,
  3. MEDETOMIDINE.
  • These are used as a hypnosedative agent.
  • Their mechanism of action =
    • ​Inhibit the neurotransmitter release of noradrenaline.
  • Noradrenaline would usually be released into the synaptic cleft but when we administer xylazine,
    • it will bind to the alpha-2-receptors and block that release.
  • These receptors can be found both post- and pre-synaptically.
  • It causes hypnosedation along with various side effects such as …. - due to …….
    • Bloating - blocking of the GI motility,
    • Hyperglycemia - reduction of insulin secretion
    • bowel atony.
79
Q

SYMPATHETIC NERVOUS SYSTEM:

Postganglionic site

β1-receptors:

A

β1-receptors:

  • The main site = heart.
  • If they are stimulated,
    • Heart will be accelerated (tachycardia)
    • Increase the contractility of the heart i.e.
      • beta-1-agonists have a positive chronotropic (accelerate the heart), and a
      • positive inotropic effect (enhance contractility).
  • Beta-1-antagonists, as well as alpha-1-antagonists, are antihypertensive agents.
80
Q

SYMPATHETIC NERVOUS SYSTEM:

Postganglionic site

β2-receptors:

A

β2-receptors:

  • These are situated in the bronchi, uterus, and blood vessels.
  • ​Therapeutically, they are used (as a beta-2-mimetic) to
  • inhibit bronchoconstriction (via bronchodilation) i.e.
    • asthma.
  • They are also used for uterus relaxation.
  • The beta-2-agonists have a vasodilating effect on the smooth muscles i.e.
    • blood vessels, however, we do not use them as vasodilators.
81
Q

SYMPATHETIC NERVOUS SYSTEM:

Postganglionic site

β3-receptors:

A

β3-receptors:

  • The beta-2-agonist should not be used as a gross promoter.
    • If these are used, they will have an influence on the beta-3-receptors
      • i.e. you can influence the quality of the meat.
      • These agonists are used to improve the quality of the meat however, they will reduce the fat content and are not tolerated.
82
Q

Drugs acting on the sympathetic nervous system:

Talking about Sympathomimetics - What is mentioned

A
  1. Pharmacological effect:
  2. Non-specific sympathomimetics:
  3. Specific sympathomimetics:
  4. Beta-2 agonists:
  5. Alpha-1-agonists
  6. Alpha-2-agonists:
83
Q

Drugs acting on the sympathetic nervous system:

Sympathomimetics:

  • Pharmacological effect: Overview
A
  1. Heart: Cardiovascular system.
  2. GI system: Smooth muscle relaxation,
  3. Respiratory system: Bronchodilation,
  4. Urinary bladder: Increased sphincter-constriction
  5. Eye: Mydriasis (iris radial muscles),
84
Q

Drugs acting on the sympathetic nervous system:

Sympathomimetics:

  • Pharmacological effect:
    1. Heart:
A

Heart:

  • Cardiovascular system.
  • If we stimulate the beta-1-receptors =
    • positive chronotropic
    • positive inotropic effect.
  • If we stimulate the alpha-1-receptors =
    • vasoconstriction
  • If we stimulate the beta-2-receptors =
    • we will cause vasodilation.
85
Q

Drugs acting on the sympathetic nervous system:

Sympathomimetics:

  • Pharmacological effect:

​GI system:

A

GI system:

  • Smooth muscle relaxation,
  • GI atony.
  • Theoretical importance, not really used therapeutically for GI Tract.
86
Q

Drugs acting on the sympathetic nervous system:

Sympathomimetics:

  • Pharmacological effect:

Respiratory system:

A

Respiratory system:

  • Bronchodilation, decreased bronchial secretion.
  • Useful in treating asthma.
  • If you would like to treat asthma,
    • you cannot do this without using a short-acting beta-2-agonist.
87
Q

Drugs acting on the sympathetic nervous system:

Sympathomimetics:

Pharmacological effect:

Urinary bladder:

A

Urinary bladder:

  • Increased sphincter-constriction (alpha-1-receptor).
  • In the case of neutering,
    • Animal can end up with incontinence (leakage of urine).
      • To treat this incontinence, you can add oestrogen derivatives and PHENYLPROPANOLAMINE which is an alpha-1-agonist.
88
Q

Drugs acting on the sympathetic nervous system:

Sympathomimetics:

  • Pharmacological effect:
A

Eye:

  • Mydriasis (iris radial muscles),
    • increase in aqueous humor production.
  • It is not used in the case of glaucoma.

​

  • When treating glaucoma,
    • we want to reduce the intraocular pressure and to do this,
    • we decrease the aqueous humor production
    • which will aid in opening the Schlemm channel
      • where the fluid can be removed easily.

= This is how intraocular pressure inside the eye is lowered.

  • In order to do this = Block the sympathetic nervous system.
89
Q

Drugs acting on the sympathetic nervous system:

Sympathomimetics:

Non-specific sympathomimetics:

A
  1. Adrenaline
  2. Noradrenaline
  3. Dopamine
90
Q

Drugs acting on the sympathetic nervous system:

Sympathomimetics:

Non-specific sympathomimetics:

1. Adrenaline

A

Adrenaline: (epinephrine)

  • Stimulate:
    • Beta-receptors
    • Alpha-1-receptors in a higher dose.
  • The dose is 0.1-0.5 mg/animal

(Ca, Fe: 0.02 mg/kg intratracheal i/v).

  • It is injected intra cardically if you would like to treat cardiac stop.
  • It can also be injected i/v but, this method is faster.
  • INDICATION=
    • Cardiac stop
    • Severe bronchoconstriction (asthma, but we have better treatments),
    • Anaphylaxis (anaphylactic shock)
      • where we can also use:
        • glucocorticoids
        • antihistamines,
        • local vasoconstriction (hemorrhages)
          • because adrenaline can act on alpha-1-receptors, and it can prolong the action of local anaesthetics e.g. LIDOCAINE by preventing it from being absorbed as quickly.
  • Lidocaine is an antiarrhythmic agent, but it can promote arrhythmia.
  • Adrenaline will prolong its effect and also causes vasoconstriction = lowers the absorption of the lidocaine.
91
Q

Drugs acting on the sympathetic nervous system:

Sympathomimetics:

Non-specific sympathomimetics:

Noradrenaline:

A

Noradrenaline:

  • It will stimulate
    • beta-1 and
    • alpha-1 receptors.
  • It is mainly used therapeutically to reduce hypertension i.e.
    • elevates the blood pressure.
  • It is injected i/v to do so.
92
Q

Drugs acting on the sympathetic nervous system:

Sympathomimetics:

Non-specific sympathomimetics:

Dopamine:

A

Dopamine:

  • The action of this drug is dependent on the dose

​= i.e. dosages are important.

  • Its low dose of 2-5 μg/kg/min, acts on the dopamine-1-receptors in the kidney.
    • ​Its effect is that you can enhance the blood circulation (perfusion) of the kidney,
      • = Useful in cases of babesiosis or ethylene glycol (antifreeze) poisoning.
  • Its medium dose of 5-10 μg/kg/min, acts on the beta-1-receptors of the heart.
    • This leads to higher tachycardia (heart rate) and
    • an increase in the blood pressure.
  • Its high dose of 10-20 μg/kg/min acts on the alpha-1-receptors (pressor).
    • The pressor effect is when the alpha-1-receptors are stimulated and lead to a lowered perfusion of the kidney i.e.
      • if the low dose is highered significantly, you can end up with the opposite effect.
93
Q

Drugs acting on the sympathetic nervous system:

Sympathomimetics:

Specific sympathomimetic drugs are?

A
  1. Dobutamine:
  • Beta-2-receptor stimulator.
  • Cardiac effect - positive chronotropic and inotropic effect.
  • This injected i/v in cases of cardiogenic shock.
  1. Isoproterenol:
  • Not fully specific as it will stimulate beta-1 and beta-2 receptors.
  • This causes:
  • acceleration of the heart,
  • bronchodilation, and the
  • increase of the oxygen being transported to the skeletal muscles via the blood vessels.
  • Therapeutic importance is not very relevant.
94
Q

Drugs acting on the sympathetic nervous system:

Sympathomimetics:

Beta-2 agonists:

A

Beta-2 agonists:

  • Therapeutic indication is:
    • bronchodilation in asthmatic patients and
    • uterus relaxant.
  • It is useful if you would like to:
    • manipulate the foetus or
    • avoid premature birth.

Beta-2 selectivity:

Clenbuterol = 4:1,

Salbutamol = 650:1,

Salmeterol = 50000:1 i.e.

  • Most specific of the three is salmeterol
    • because the higher the ratio,
    • Lower the cardiac effect.
    • Salmeterol will have an effect mainly on the beta-2-receptors and you will not affect the beta-1-receptors.
  • If you have 2 asthmatic patients with a high blood pressure and add clenbuterol to one and salmeterol to the other,

= Asthma will be relieved in both due to the

  • Action on the beta-2-receptors but at the same time in clenbuterol, the beta-1-receptors will also be stimulated
    • i.e. the blood pressure will further increase.
  • This is why it is better to use salmeterol. All in all, you will have less of a side effect e.g.
    • tremor and excitation, when using salmeterol.

​Indications:

  • Horse RAO,
  • feline asthma,
  • bronchitis,
  • bronchopneumonia,
  • tracheal hypoplasia,
  • tracheal collapse.

Dosages:

  • Clenbuterol: horse = 1-3 μg/kg PO
  • Salmeterol: 100-200 μ/cat, 360-720 μ/horse.
95
Q

Drugs acting on the sympathetic nervous system:

Sympathomimetics:

Name Beta-2 agonists:

A

Beta-2 agonists:

  1. CLENBUTEROL,
  2. SALBUTAMOL,
  3. TERBUTALINE,
  4. SALMETEROL,
  5. ISOXSUPRINE etc.
96
Q
A
97
Q

Drugs acting on the sympathetic nervous system:

Sympathomimetics:

Alpha-1-agonists:

A

Alpha-1-agonists:

  • If we stimulate the alpha-1-receptors we end up with vasoconstriction.
  • This can be good when used topically e.g. in
    • nasal congestion
      • Blood vessels are constricted inside the nose and make more room for air.
98
Q

Drugs acting on the sympathetic nervous system:

Sympathomimetics:

Name Alpha 1 agonists

A
  1. PHENYLEPHRINE:
  2. XYLOMETAZOLINE, OXYMETAZOLINE, NAPHAZOLINE, TETRYZOLINE:
  3. PHENYLPROPANOLAMINE:
  4. EPHEDRINE:
99
Q

Drugs acting on the sympathetic nervous system:

Sympathomimetics:

Specific sympathomimetic

Alpha-1-agonists:

PHENYLEPHRINE

A

PHENYLEPHRINE:

  • Used rarely.
  • Act on the alpha-1-receptors to cause vasoconstriction.
  • It is used locally in cases of allergies and colds and
  • Used systematically in cases of hypotension and shock (not relevant).
100
Q

Drugs acting on the sympathetic nervous system:

Sympathomimetics:

Specific sympathomimetic

Alpha-1-agonists:

XYLOMETAZOLINE, OXYMETAZOLINE, NAPHAZOLINE, TETRYZOLINE:

A

XYLOMETAZOLINE, OXYMETAZOLINE, NAPHAZOLINE, TETRYZOLINE:

  • Also act on the alpha-1-receptors to cause vasoconstriction
  • Used locally.
  • Tetryzoline administered as eye drops
  • constrict the blood vessels
  • Stop the redness in your eye
  • It will dry out the eye.
101
Q

Drugs acting on the sympathetic nervous system:

Sympathomimetics:

Specific sympathomimetic

Alpha-1-agonists:

PHENYLPROPANOLAMINE:

A

PHENYLPROPANOLAMINE:

  • It is used with estrogen derivatives to treat incontinence in bitches post-neutering.
  • Act on the alpha-1-receptors to cause urinary bladder sphincter constriction.
  • It is administered orally on an empty stomach.
  • It has many side effects.
102
Q

Drugs acting on the sympathetic nervous system:

Sympathomimetics:

Specific sympathomimetic

Alpha-1-agonists:

EPHEDRINE:

A

EPHEDRINE:

  • It can be used as oral administration for incontinence,
    • but it has a CNS effect i.e.
      • it is a mild amphetamine (a psychostimulant).
  • Non-specific,
  • Direct,
  • Indirect effects.
  • It causes tachyphylaxis (a faster developing tolerance).
  • Usually, tolerance can occur within weeks but, with tachyphylaxis, tolerance can occur within hours or days i.e.
  • it must increase the dosage in order to achieve a similar effect.
103
Q

Drugs acting on the sympathetic nervous system:

Sympathomimetics:

Specific sympathomimetic

Alpha-2-agonists:

A

Alpha-2-agonists:

  • Sedatohypnotics:
  1. XYLAZINE,
  2. DETOMIDINE,
  3. MEDETOMIDINE,
  4. ROMIFIDINE.
104
Q

Drugs acting on the sympathetic nervous system:

Sympatholythics

A

Sympatholytics: Block the sympathetic nervous system.

  1. Non-specific alpha-antagonists:
    • ​Used for urethra sphincter relaxation.
  2. Alpha-1-antagonists:
  3. Alpha-2-antagonist:
  4. Non-specific beta-antagonists:
    • The main indication is to treat
      • hypertension,
      • arrhythmia, and
      • hyperthyroidism.​
  5. ​​Specific beta-1-antagonists
105
Q

Drugs acting on the sympathetic nervous system:

Sympatholythics

Non-specific alpha-antagonists:

A

Non-specific alpha-antagonists:

  • Used for urethra sphincter relaxation.
  • Therapeutically used if there are urinary difficulties.
  • These are also used in cases of pheochromocytoma.
    • This is when there is a benign tumor in the medulla and the final result is a hypertensive crisis.
  • If you apply 1. or 2. you can treat this high blood pressure.
  1. PHENOXYBENZAMINE: long duration of action.
  2. PHENTOLAMINE
  3. TOLAZOLINE
106
Q

Drugs acting on the sympathetic nervous system:

Sympatholythics

Alpha-1-antagonists:

A

Alpha-1-antagonists:

  1. PRAZOSIN:
  • ​Used to treat hypertension by causing vasodilation and
  • can reduce the blood pressure.
  1. DOXAZOSIN: Used for urethra sphincter relaxation.
107
Q

Drugs acting on the sympathetic nervous system:

Sympatholythics

Alpha-2-antagonist:

A
  1. ATIPAMEZOLE: Used in cases of overdose.
  2. YOHIMBINE
108
Q

Drugs acting on the sympathetic nervous system:

Sympatholythics

Non-specific beta-antagonists:

A

Non-specific beta-antagonists:

The main indication is to treat

  • hypertension,
  • arrhythmia, and
  • hyperthyroidism.
109
Q

Drugs acting on the sympathetic nervous system:

Sympatholythics

Non-specific beta-antagonists:

PROPRANOLOL:

A
  • Acts on beta-1 and beta-2-receptors.
  • Its main indication is to treat high blood pressure.
  • With this treatment, it will also cause bronchoconstriction due to stimulation of the beta-2-receptors i.e.
    • if you have a patient with asthma, it will induce an asthmatic attack as it is non-specific.
      • For treating asthma, use a specific beta antagonist instead.
110
Q

Drugs acting on the sympathetic nervous system:

Sympatholythics

Non-specific beta-antagonists:

TIMOLOL:

A
  • Indication (other than hypertension) is as eye drops in cases of glaucoma.
  • Not only will it reduce the aqueous humor production, but it will also
  • Open the Schlemm channel to allow for the outflow of fluid .
111
Q

Drugs acting on the sympathetic nervous system:

Sympatholythics

Specific beta-1-antagonists

A

Specific beta-1-antagonists:

  1. METOPROLOL
  2. ATENOLOL

Veterinary Pharmacology (21 decks)

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