DRUGS Flashcards
Pilocarpine
MECHANISM OF ACTION:
- Muscarinic receptor agonist
- Causes myosis (pupillary constriction), promotes drainage
- Mimics Ach in turn promoting parasympathetic stimulation
USE:
- Drops used in eyes
- Treatment for glaucoma (increase intra-ocular pressure)
- Can be used in conjunction with mydriatics (dilators) to prevent adhesion
SIDE EFFECTS: HR: - GIT: +++ Bladder Contraction: ++ Myosis: +++
Bethanechol (Urocarb)
MECHANISM OF ACTION:
- Muscarinic receptor agonist
- Mimics ACh in turn promoting parasympathetic stimulation
USE:
- Used post operatively to stimulate GIT
- Can be in drop form (ophthalmic)
SIDE EFFECTS: HR: - GIT: +++ Myosis: ++ Bronchoconstriction Increased secretions
Carbachol
MECHANISM OF ACTION:
- Muscarinic receptor agonist
USE:
- Could be used post-surgery to stimulate GIT
- Comes in drop form – myosis
SIDE EFFECTS:
Myosis: ++
GIT: ++
Bronchoconstriction
Atropine (Atrosite)
MECHANISM OF ACTION:
- Muscarinic Antagonist (competitive antagonist)
- Binds to the same site as ACh/ muscarinic agonist, but doesn’t activate it (blocks agonist from binding)
- readily absorbed
USE:
- Used as a premed for anesthesia
- Treatment for OP poisoning (reversal)
SIDE EFFECTS: HR: ++ Mydriasis: ++ GIT: - - Prevents bronchoconstriction Urinary retention Dries up secretions (lacrimal, salivary, bronchial)
Pancuronium (Pavulon)
MECHANISM OF ACTION:
- Nicotinic Competitive antagonist – competitively binds cholinergic receptor sites inhibiting ACh
NB: SHORT ACTING
USE:
- Used adjacent to general anesthetic to produce muscle relaxation
- Muscular paralysis & Paresis
- Reversibly by Cholinesterase inhibitor
SIDE EFFECTS: HR: + BP: + Hypersalivation Caution: Myasthenia Gravis
Vecuronium (Norcuron)
MECHANISM OF ACTION:
- Competitive nicotinic antagonist (non-depolarizing)
- Competitively binds cholinergic receptor sites inhibiting ACh
- MORE POTENT THAN PANCURONIUM (3x)
- SHORT ACTING (shorter than pancuronium)
USE:
- Causes muscular paralysis/ paresis
- Reversibly by Cholinesterase inhibitor
SIDE EFFECTS:
- Caution: Myasthenia gravis
- Beware recovery and ‘spare’ receptors (i.e. 80% occupied, yet ‘recovered’/ animal has muscle movement again)
- Does not pass BBB
Physostigmine
Neostigmine
Edrophonium
MECHANISM OF ACTION:
- Cholinesterase Inhibitor
- Reversibly inhibits the destruction of ACh by anticholinesterase, thereby increasing ACh at the receptor site
- Crosses BBB, therefore, inhibits cholinesterase’s centrally and peripherally
USE:
- Used in the diagnosis and treatment of myasthenia gravis (prolongs the action of ACh at receptor sites/ NM junction)
SIDE EFFECTS:
Risk of toxicity therefore should have Atropine on hand (stops the ACh binding)
Toxic doses: Bradycardia Bronchial constriction Hypersalivation Muscle weakness
Salbutamol (Ventolin)
MECHANISM OF ACTION:
- Beta 2 agonist (selective)
- Relaxation of smooth muscle of bronchi & bronchioles (airway dilation)
- Dilates blood vessels in skeletal m.
USE:
- Tablets or inhalants
- Treatment for feline asthma (with Glucocorticosteroids)
- Treatment for chronic obstructive pulmonary disease in horses
SIDE EFFECTS:
- Uterine relaxation
- Bronchial relaxation
- Relaxation of detrusor m.
- Induced hyperglycemia
Acute toxicity:
- Tachycardia, hypertension, tremors
Adrenaline (Epinephrine)
MECHANISM OF ACTION:
- Alpha 2 & Beta 1 receptor agonists
- Causes vasoconstriction (arteries and arterioles)
- Increased glycogenolysis and raised blood sugar
USE:
- Emergency: Patient flatlining
- Can be used prior to antiserum administration and prior to blood transfusions to deter anaphylaxis
- Sometimes can be used in conjunction with local anesthetics (stops drug from drifting away from the surgery site)
SIDE EFFECTS:
BP: +++
HR: +++
Myosis: ++
Can cross the placenta and into milk
Xylazine (Rompun)
MECHANISM OF ACTION:
- Alpha 2 receptor adrenergic agonist
- Causing skeletal muscle relaxation
- Causes CNS depression
USE:
- Used as sedation (pre-anesthetic) before local or general anesthetic.
- Short period of analgesia for “healthy animals” – some risk associated with small animals
- Primary used in horses and cattle
SIDE EFFECTS:
- May cause emesis in cats and some dogs
- Initial increase in BP, followed by a prolonged period of depressed BP (below baseline).
- Depresses thermoregulatory mechanisms (hypothermia and hyperthermia possible).
Medetomidine (Domitor)
MECHANISM OF ACTION:
- Alpha 2 receptor agonist
- Depression of the CNS (sedation), GI (decreased secretions), muscle relaxation (not enough for intubation)
USE:
- Used as a sedative and analgesia
- Primary use in small animals – dogs, cats, exotics, and small mammals
SIDE EFFECTS: GIT: - - Bradycardia Hypothermia Respiratory depression Vasoconstriction Can cause cyanotic mucous membranes
Dopamine (Intropin)
MECHANISM OF ACTION:
- “All-rounder” (Stimulates a1, a2, B1, B2)
- Rapidly metabolized in GIT (therefore cannot administer orally, must be IV, IM, SC)
- Precursor to norepinephrine and acts directly and indirectly (by releasing norepinephrine) on both alpha and beta receptors
USE:
- Critical Care Drug (ICU)
- Often used post-cardiac arrest for their positive inotrope action
- Can be used during surgery to maintain HR and BP
SIDE EFFECTS: Can cause nausea and vomiting Tachycardia Palpitation Hypotension Dyspnoea Vasoconstriction
Low dose: (0.5-2ug/kg/min)
Dilation of renal (Improve GFR), mesenteric, cerebral, coronary, and intracerebral vascular beds.
Intermediate dose: (2-10ug/kg/min)
Stimulates
Metoprolol (Lopressor)
MECHANISM OF ACTION:
- Beta 1 blocker (specific)
- Blocks sympathetic innervation to the myocardium and as a result causes an increase in ventricular filling
USE:
- Use in supraventricular tachyarrhythmias and systemic hypertension
- Treatment for cats with hypertrophic cardiomyopathy
SIDE EFFECTS:
- Decreased sinus HR, slowed AV conduction, and diminished cardiac output (beware CHF patients)
- Blocks glycogenolysis (beware diabetic patients)
- Inhibits bronchodilation (beware asthma patients)
Atenolol (Tenormin)
MECHANISM OF ACTION:
- Selective Beta 1 antagonist (blocker)
- Slows down the heart, and as a result, allows the heart to fill properly
USE:
- Used in the treatment of cardiovascular disease
- Use in tachycardia, tachyarrhythmias, hypertrophic heat wall disease.
SIDE EFFECTS:
- Hypotension
- Lethargy
- Diarrhea
- Blocks glycogenolysis
- Caution in animals with CHF, asthma, diabetes, and hypoglycemia
Propanolol (Inderal)
MECHANISM OF ACTION:
- Non-selective Beta 1 & Beta 2 antagonist
- Blocks both Beta 1 and Beta 2 receptors in the myocardium, bronchi, and smooth muscle.
USE:
- Use for antiarrhythmic effects. Use for dysrhythmias
- Improves cardiac performance in animals with cardiomyopathy
SIDE EFFECTS:
- Inhibits bronchodilation (beware asthma patients)
- Decreases cardiac contractions (beware CHF/ heart patients)
- Blocks glycogenolysis (beware diabetic/ hypoglycaemic patients)
Phenoxbenzamine
Dibenzyline
MECHANISM OF ACTION:
- Non-selective alpha 1 & 2 antagonist
- Alpha-adrenergic response to circulating epinephrine and norepinephrine is non-competitively blocked by Phenoxbenzamine
USE:
- Use in reducing urethral sphincter tone
- Treatment of hypertension
- Use in preventing and treating laminitis in its early stages
- Treatment of some secretory diarrhea
SIDE EFFECTS:
- Use with cautions in patients with CHF or other heart diseases, as drug-induced tachycardia
Phenylephrine
MECHANISM OF ACTION:
- Alpha 1 receptor agonist
USE:
- Used to increase blood pressure or topically to control bleeding
SIDE EFFECTS:
- Vasoconstriction
- Not a replacement for fluid therapy for patients with shock to increase BP
- Reflex bradycardia (can be blocked by atropine)
- Restlessness and headache
- Mydriasis: ++
Lignocaine/ Lidocaine
MECHANISM OF ACTION:
- Combines with fast sodium channels when inactive which inhibits recovery after repolarisation.
- Rapid onset with 1-2 hr duration
USE:
- Local Anaesthetic & anti-arrhythmic agent (ventricular tachycardia)
- In horses, used postoperatively to prevent post-operative ileus and reperfusion injuries
- Can be used as a topical spray prior to painful injections
SIDE EFFECTS:
- Cats more sensitive to cardio depressant effects of the drug
Prazosin (Minipres)
MECHANISM OF ACTION:
- Selective competitive Alpha 1 antagonist (blocker)
- Vasodilation (arteries and venous side) causing a reduction in BP
USE:
- Adjunctive treatment for CHF and hypertension in dogs
- Also used to treat functional urethral blockages/ obstructions in dogs and cats (reduced sympathetic tone)
SIDE EFFECTS:
BP: - -
Reduced peripheral vascular resistance
Vasodilation of arteries and venous side.
Caution: patients with chronic renal failure or animals with pre-existing hypotension
Apomophine (meditate)
MECHANISM OF ACTION:
- Dopamine agonist
- Stimulates dopamine receptors in the chemoreceptor trigger zone, thus inducing vomiting.
USE:
- Used as an emetic in dogs and not cats (xylazine is more effective for felines)
SIDE EFFECTS:
Emesis: +++
Risk: aspiration
Caution: Rabbits and rodents (unable to vomit and stomach walls unable to tolerate emesis).
CNS Excitation/ depression
NB: Emetics only remove 40-60% of stomach contents
Metoclopramide (Maxolon)
MECHANISM OF ACTION:
- Dopamine antagonist
- Blocks the uptake of dopamine at the chemoreceptor trigger zone
USE:
- Used as an anti-emetic in dogs, cats, and small mammals to control nausea
- Used also to stimulate the motility of the upper GIT, increasing peristalsis
- Treatment of gastroesophageal reflux disorders
SIDE EFFECTS:
Emesis: —
Caution: do not use on animals with a history of seizures as it may lower the seizure threshold
Succinylcholine/ Suxamethonium
MECHANISM OF ACTION:
- Depolarising neuromuscular blocking agent
- Bonds with motor endplate cholinergic receptors to produce depolarisation causing flaccid paralysis
USE:
- Short term muscle relaxation needed for surgical or diagnostic procedures.
- No Analgesia
SIDE EFFECTS:
- Muscle Paralysis/ paresis
- Hyperthermia
- Excessive salivation
- Hyperkalaemia
- Bradycardia/ tachycardia
- Hypertension/ hypotension
- Arrhythmias
Atipamezole
MECHANISM OF ACTION:
- Alpha 2 adrenergic antagonist
- Competitively inhibits alpha 2 adrenergic receptors, thereby acting as a reversal agent to reduce sedation of Alpha 2 agonist drugs
USE:
- Reversal agent used for medetomidine sedation agent or Xylazine
SIDE EFFECTS:
- Vomiting/ Diarrhoea
- Hypersalivation
- Tremors
- Brief excitation/ apprehensiveness
Dobutamine
MECHANISM OF ACTION:
- Selective Beta 1 agonist
- Mild beta 2 and alpha 1 adrenergic effect
- Does not cause the release of norepinephrine
USE:
- Used as a short-term treatment of heart failure, to increase cardiac output.
SIDE EFFECTS:
- Caution: Patients with ventricular tachycardias
- Tachycardia
- Increased BP
Norepinephrine/ Noradrenaline
MECHANISM OF ACTION:
- Alpha receptor agonist
- Causes vasoconstriction, which in turn causes an increase in BP
USE:
- Treatment of profound hypotension
- Short half-life – approximately two mins
SIDE EFFECTS:
- Skin sloughing if administered dermally (administer via central line)
Ondanzetron
MECHANISM OF ACTION:
- 5-HT3 (serotonin type III) receptor antagonist
- These receptors are found peripherally on the vagal n. terminals and centrally within the chemoreceptor trigger zone.
USE:
- Used as an antiemetic in dogs for severe vomiting (use when other conventional antiemetics are ineffective
SIDE EFFECTS:
- Don’t use in cats (controversial)
- Constipation
- Sedation
- Arrhythmias
- Hypotension
Isoprenaline/ Isoproterenol
MECHANISM OF ACTION:
- Non-selective B1 & B2 agonist
- Relaxes bronchial smooth muscle causing bronchodilation and peripheral vasodilation. Stimulates Beta 1 receptors causing an increase in heart rate and contractility.
USE:
- In patients experiencing cardiac arrest, and airway collapse
- As adjunctive therapy in heart failure or shock (not an adequate replacement for fluid therapy)
SIDE EFFECTS:
- Tachycardia
- Vomiting
- Tremors
- Anxiety
