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Veterinary Pharmacology > Drugs MT II > Flashcards

Drugs MT II Flashcards

1
Q

Autonomic nervous system

Parasympathetic nervous system

Receptor and subtype

A
  1. ACh R is a Na channel -> if activated ⇒ Na influx ⇒ Depolarisation
  2. Muscarinic ACh R is a G-protein-coupled R -> if ACh is bound ⇒ G-protein cascade is activated.
  3. There are 5 subtypes, but mainly focus on M1, M2, M3
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2
Q

Autonomic nervous system

Parasympathetic nervous system

M1 and M3

A

M1,M3

  • Stomach and glands,
  • bronchial SM,
  • eye ciliary muscle (cause miosis)

Indirectly cause vasodilation via NO

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3
Q

Autonomic nervous system

Parasympathetic nervous system

M2

A

○ M2

■ Heart

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4
Q

Autonomic nervous system

Parasympathetic nervous system

○ Symptoms: “Sludge”

A

○ Symptoms: “Sludge”

Salivation

Lacrimation

Urination

Digestion

GI irritation

Emesis

Others: bradycardia, bronchoconstriction, miosis

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5
Q

Autonomic nervous system

Parasympathetic nervous system

parasympathomimetics

A

= cholinergic drugs

● Drugs that act on the parasympathetic NS

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6
Q

Parasympathomimetics = cholinergic drugs

● Drugs that act on the parasympathetic NS

● Pharmacological effects acts on:

A

○ Eye:

○ Cardiovascular system:

○ GI-tract:

○ Respiratory tract:

○ Urinary tract:

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7
Q

Parasympathomimetics = cholinergic drugs

● Drugs that act on the parasympathetic NS

● Pharmacological effects EYE

A
  • Constrict iris sphincter muscle ⇒ Constricting pupil will ↓ intraocular pressure (useful in glaucoma)
  • Keratoconjunctivitis sicca (KCS) -> dry eye disease (autoimmune disease)
  • Parasympathomimetics ⇒ ↑ lacrimal secretion (symptomatic treatment)
  • Causative treatment -> immunosuppressants (e.g. cyclosporine, pimecrolimus)
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8
Q

Parasympathomimetics = cholinergic drugs

● Drugs that act on the parasympathetic NS

● Pharmacological effects - Cardiovascular system

A
  • Negative chronotropic effects (bradycardia)
  • ∅ inotropic effect (∅ contractibility effect)
  • Vasodilation via NO (indirect)
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9
Q

Parasympathomimetics = cholinergic drugs

● Drugs that act on the parasympathetic NS

● Pharmacological effects: GI-tract:

A
  • SM constriction
  • Glandular hyperfunction (↑ secretion)
  • Vomiting, diarrhoea
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10
Q

Parasympathomimetics = cholinergic drugs

● Drugs that act on the parasympathetic NS

● Pharmacological effects: GI-tract: Respiratory tract:

A
  • Bronchoconstriction (must be careful in patients with asthma)
  • ↑ bronchial secretion
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11
Q

Parasympathomimetics = cholinergic drugs

● Drugs that act on the parasympathetic NS

● Pharmacological effects: Urinary tract:

A
  • Bladder contraction
  • Sphincter relaxation
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12
Q

● Direct parasympathomimetics

A

○ Bind to ACh Rs

  1. Acetylcholine (ACh)
  2. Carbachol
  3. Pilocarpine
  4. Bethanechol
  5. Methacholine
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13
Q

● Direct parasympathomimetics

Acetylcholine (ACh)

A

● Direct parasympathomimetics

  • Non-specific (N and M-ACh Rs)
  • Non-selective
  • Cannot be used therapeutically because of very short half-life
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14
Q

● Direct parasympathomimetics

CARBACHOL

A

● Direct parasympathomimetics

Old and obsolete

Non-specific to M-ACh Rs

Local administration only

Indications:

● Used to treat glaucoma (eye drops, obsolete drug)

● In uterus to treat metritis (intrauterine tablet)

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15
Q

● Direct parasympathomimetics

PILOCARPINE

A

● Direct parasympathomimetics

Natural alkaloid

Side effects are mild after administration

Indications:

● Glaucoma (miosis can be seen within 15 min)

● Keratoconjunctivitis sicca (KCS)

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16
Q

● Direct parasympathomimetics

BETHANECHOL

A

● Direct parasympathomimetics

Human

M-ACh R specific (less side effects)

Starts up bowel movement after surgery

Induce urination

17
Q

● Direct parasympathomimetics

METHACHOLINE

A

● Direct parasympathomimetics

Human

M-ACh specific

Application is rare (theoretically it’s useful for atrial fibrillation, but practically it is not)

Indications:

● Ergot toxicosis, which leads to serious vasoconstriction ⇒ brain damage

18
Q

Indirect parasympathomimetics

A

○ ACh esterase enzyme inhibition

⇒ ↓ ACh degradation ⇒ ↑ [ACh]

○ Contains a carboxylic acid group which binds to esteratic site and inactivates it for 1-6 hrs (i.e. ACh cannot bind and be down by ACh esterase enzyme)

○ Organophosphates

○ Physostigmine

○ Neostigmine

○ Pyridostigmine

○ Edrophonium

19
Q

Indirect parasympathomimetics

ORGANOPHOSPHATES

A

Irreversible binding! ⇒ excess ACh TOXICOSIS

First sign

⇒ parasympathomimetic effect (salivation, emesis, diarrhoea etc)

Severe ⇒ tremors, convulsions, seizures

⇒ ↑ body temperature ⇒ death

Effects:

● Salivation
● Diarrhoea
● emesis
● Convulsions

● Tremors

Antidote:

  • Atropine
    • Tropane alkaloid
    • ↑ dose => ↑ symptoms (can cross BBB => hallucinations, coma)
    • Dose: 0.01-0.02mg/kg IM/IV (narrow TI)
  • Pralidoxime
    • AChE activator
    • Works only shortly after organophosphate administration. If given later, it’ll have no effect (timing = important!)
20
Q

Indirect parasympathomimetics

PHYSOSTIGMINE

A
  • Tertiary N -> can cross BBB => small TI
  • Lipophilic
  • Topically -> eye drops, however, tolerance can occur!
  • Can be used in case of atropine poisoning
21
Q

Indirect parasympathomimetics

NEOSTIGMINE

A
  • Quaternary N -> ∅ cross BBB
  • ∅ Po (absorption = very bad)
  • IV, IM
  • Eye drop -> treatment of glaucoma (tolerance can occur!)

Indications:

  • Myasthenia gravis (an autoimmune disease that destroys ACh Rs)

Effects:

  • Suspends action of nondepolarizing muscle relaxants because they’re competitive antagonists of this R
  • Restores function of SKM
  • ↑ intestinal motility
  • Induces emesis
22
Q

Indirect parasympathomimetics

PYRIDOSTIGMINE

A

Quaternary N (∅ crossing BBB)

Po (F= 3-8%)

Indications:

  • Myasthenia gravis

↑ intestinal motility

23
Q

Indirect parasympathomimetics

EDROPHONIUM

A
  • Competitive inhibition in neuromuscular junction -> action is suspended by diffusion
  • Short DOA -> 5-15 min
  • Used in diagnosis of myasthenia gravis (Tensilon test)
24
Q

Parasympatholytics = anticholinergic drugs

A
  • Muscarinic R antagonist
  • Atropine

Parasympatholytics = anticholinergic drugs

  • Tropane alkaloid
  • Dose: 0.01-0.02mg/kg
25
Q

Parasympatholytics = anticholinergic drugs

Pharmacological effects ON:

A

■ Eye:

■ Cardiovascular:

■ GI-tract:

■ Bronchi:

26
Q

Parasympatholytics = anticholinergic drugs

Pharmacological effects ON:

EYE

A

● CYCLOPLEGIA -> accommodation disturbance due to paralysis of ciliary muscle. It is very painful and atropine can be applied to relieve the pain (alleviate muscle spasms)

● Eye EXAMINATION-> use derivatives

  • (tropicamide, homatropine)
    • because atropine has a much longer DOA in healthy eyes (1 day);
    • bad eyes = much shorter (why atropine is given 3-6x/day in unhealthy eyes)

● SYNECHIAE -> fibrin deposits that will cause iris to irreversibly attach to cornea or lens.

  • Atropine and its derivatives can be applied to prevent the cornea from binding by dilating the pupils
27
Q

Parasympatholytics = anticholinergic drugs

Pharmacological effects ON:

CARDIOVASCULAR

A

● Tachycardia by lifting the cholinergic blockade of heart

(n.vagus)

● ∅ effect on blood vessels

28
Q

Parasympatholytics = anticholinergic drugs

Pharmacological effects ON:

GI-TRACT

A

● ↓ gastric secretion and salivation

(important in premedication)

● Transit time ↑

● Causes constipation

29
Q

Parasympatholytics = anticholinergic drugs

Pharmacological effects ON:

BRONCHI

A

● Bronchodilation

● ↓ mucus secretion (premedication)

30
Q

Parasympatholytics = anticholinergic drugs

Indication

A

○ Indications:

  1. Premedication:

● Antagonizing bradycardia, however ∅ influence on blood

vessels -> can be dangerous before α-2 agonist administration

(vasoconstriction)

● ↓ saliva production

● ↓ bronchial secretion, bronchodilation

● Glycopyrrolate is better than atropine!!!

○ Glycopyrrolate -> doa on heart: 2-3 min, doa on bowel movement inhibition: 7 hrs, ↓ CNS side effects (∅ BBB crossing)

○ Atropine -> doa on heart: 20-30 min, doa on bowel movement inhibition: 1.5 hrs

  1. Bronchodilation:

● Fe, Hu = asthma; eq = RAO (recurrent airway obstruction) ↔

COPD (chronic obstructive pulmonary disease)

● Ipratropium

○ DOA = 6 hrs

○ ∅ crossing BBB

  1. Atropine as antidote:

● Organophosphate toxicosis

  1. Antidiarrheals:

● Atropine will ↓ secretion and bowel movement (peristalsis and segmental contractions = inhibited)

● Atropine -> used for obstipation

● Benzethimid

○ Ru

○ ↓ secretion and motility
● Use morphine derivatives instead because it doesn’t affect

segmental contraction (only longitudinal)

  1. Antispasmodics:

● Atropine ↓ SM function -> antispasmodic effect in the intestine

● Effective in eq colic (esp. butyl-scopolamine)

Other:

● Treatment of Parkinson-disease in Hu

  1. ○ Toxicity

Small TI

Rabbits are relatively resistant (liver atropine) whereas eq are quite sensitive

Symptoms: dry mouth, tachycardia, mydriasis, constipation, convulsions, coma, death

Veterinary Pharmacology (21 decks)

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