Pharmacology Concepts/ Definitions Flashcards
(34 cards)
Grand mal
Intra cranial causes include: Encephalitis, hydrocephalus, trauma, epilepsy
Extracranial causes include Hepatoecephalopathy, toxicity (lead, paraldehyde), hypoglycemia & hypocalcemia.
Typically 4 phases:
- Prodromal: mild behavior change
- Aura: pronounced change in behavior prior to seizure
- Fit/ seizure
- Post ictal: associated with disorientation (these are characterised from human experience)
Petit mal
Partial Seizure:
- Characterized by a short period of unconsciousness
- May not be common in animals
- Sometimes classed as a partial seizure or focal seizure
Jacksonian seizure: slow-moving tonic spasm in appendage
Psychomotor: unusual behaviors
NB: In all cases seizures are a result of overstimulation and excessive electrical activity
Phenothiazines
Dopamine antagonist + anticholinergic, anti-histamine, and adrenergic (α) blocker
- Antiemetic
- Not useful for seizures or storms/fireworks
- No analgesia!
- Hypotensive
Examples: Acepromazine, Chlorpromazine, Promazine.
S.L.U.D.G.E - symptoms of Organophosphate poisoning
- Salivation
- Lacrimation
- Urination
- Defecation
- Gastrointestinal problems
- Emesis
a1 Receptor
- Activation causes the release of intracellular Ca2+ stores excitatory effects
- Found mainly on smooth muscle (contraction)
- Decreased smooth m. motility (GIT)
- Mydrisis (pupil dilation)
- Sphincter contraction (Bladder)
- Increased glycogenolysis (Liver)
a2 Receptor
- Activation causes inhibitory effects
- Located pre-synaptically (pre-synaptic inhibition of NA release)
- Decreased smooth m. motility (GIT)
- GIT sphincter constriction
B1 Receptor
- Activation causes increased Ca2+ conductance
- Located mainly on cardiac muscle (increased HR and contractility)
- Receptor on the heart that causes it beat faster and stronger
B2 Receptor
- Activation causes phosphorylation of intracellular proteins
- Located mainly on smooth muscle (relaxation)
- Dilates (causes bronchodilation, vasodilation)
- Decreased smooth muscle motility (GIT)
- Smooth m. relaxation (bladder)
- increased gluconeogenesis
B3 Receptor
- Found mainly on adipose tissue (lipolysis & thermogenesis)
- Mainly associated with hibernation of animals
Tricyclic Antidepressants
Three main effects of these drugs:
- Block reuptake of amines
- Anticholinergic (muscarinic)
- (also H1 and α1 adrenergic antagonist)
- Sedative
- Required twice a day
Dogs: Anxiety, some aggression, separation anxiety, noise phobias, OCD
Cats: Anxiety, spraying, over-grooming
Example Drugs:
Amitriptyline: Used in small animals, takes 10-14+ days
Nortriptyline: Has active secondary metabolites
Doxepin: Has anti histamine effects, Useful for anxious pruritus
Clomipramine: 200X serotonin > norepinephrine, generally for OCD, takes 6-8 weeks to take effect, can permanently affect neuroreceptor (withdraw use)
Side Effects:
- Sedation
- Anti cholinergic = dry mouth, increased thirst, urinary retention, constipation
- Tachycardia
- Ataxia
SSRI’s (Selective Serotonin Reuptake Inhibitors)
Cats: anxiety, spraying, OCD
Dogs: Anxiety, some aggression, separation anxiety, noise phobias, OCD
- Require 6-8 weeks to effect
- Only need once a day
Side effects:
- Hepatic/ Liver dysfunction
- GIT (lots of serotonin receptors), diarrhoea
- Increased anxiety
Example drugs:
Fluoxetine, Fluvoxamine, Paroxetine, Sertraline
Monoamine oxidase inhibitors (MAOI’s)
Monoamine oxidase inhibitors (MAOI’s)
- Selegiline Fears, phobias and age-related problems esp. canine cognitive dysfunction
Side effects:
- GI effects, restlessness or lethargy, anorexia
- Hyperactivity
- Depression
Contraindication:
- Do not combine with SSRIs, ephedrine, opioids, phenylpropanolamine
Glucocorticosteroids
- Corticosteroids stabilise cell membranes and prevent release of arachidonic acid (and histamine), which disrupts the inflammatory mediator pathway
- Induce gluconeogenesis in the liver
- Provide some control over allergies
- NOT analgesics
- Delay healing
- Increase susceptibility to infections (may activate latent infections)
- Antagonize insulin (beware diabetic patients)
- NOTE: Adverse side effects are dose and/or frequency related
USE:
- Control of immune mediated diseases
- Reduce inflammation and scarring
NSAIDs
- NSAIDs stop the release of COX-1 and COX-2, blocking pain (nociception).
- Can have COX specific and dual inhibitor NSAIDs depending on the desired outcome.
COX-1
COX-1:
- Inhibition is often undesirable
- Homeostatic function
- Nociceptor sensitization (central & peripheral)
- Increased gastric mucus secretion
- Reduced acid secretion
- Increased bicarbonate secretion
- Increased gastric mucosal cell turnover
- Increased platelet aggregation (clotting)
COX-2
COX-2:
- Inhibition often is desirable
- Inflammation
- Nociceptor sensitization
- Vasodilation
- Inhibition of platelet aggregation
- Increased Na excretion (inhibited reabsorption)
- Altered renal blood flow
Antiarrhythmic Drugs
Class One (I):
- Membrane stabilisers that block voltage-gated sodium channels
- Increases the refractory period
- Class 1a, 1b, 1c
Class Two (II):
- B blockers that antagonize adrenergic receptors
- Slow AV conduction and reduce contractility
- Longer fill time (reduced HR)
- Decreased oxygen demand in the myocardium
- Propranolol (non-selective), atenolol (selective B1)
Class Three (III):
- K+ channel blockers
- Antifibrillatory
(e. g.) Amiodarone, Sotalol
Class Four (IV):
- Ca channel Blockers
- Decreased heart rate
- Decreased AV conduction and decreased contractility
(e. g.) Verapamil and Diltiazem
What concurrent findings accompany severe liver disease?
- Ascites/oedema/pulmonary oedema (from hypoproteinaemia)
- Polyuria (decreased urea synthesis)
- Anaemia
- Hypocalcaemia ( decrease in albumin bound Ca and decrease in Vitamin D conversion)
- Hypoglycaemia
- Hypothermia
- Blood clotting
- Jaundice
- Increase in blood ammonia, bile acids, acid base & electrolyte abnormalities
- Hepatic encephalopathy
- Autonomic dysfunction (esp. chronic liver disease) causes increased circulating vasodilators and decreased response to vasoconstrictors
Type A Adverse Drug Reactions
Type A (augmented) reactions:
- Expected but exaggerated pharmacological or toxic responses to a drug
- Primary response exaggeration of the intended response (absolute or relative overdose)
- Secondary response affecting an organ other than the target (side effects)
- The reaction is predictable, dose dependent and usually avoidable.
- Includes the normal side effects of the drug
(E.g.)
- Tachycardia with β2 adrenoceptor agonist bronchodilators (e.g. salbutamol, terbutaline)
- Hypotension with Acepromazine
Type B Adverse Drug Reactions
Type B (Bizarre) reactions:
- Not related to the drug’s expected pharmacological effects
- Unpredictable, dose independent, difficult to avoid
- High mortality
- Drug allergies or drug hypersensitivity reactions
(e. g.) Penicillin allergy - Idiosyncratic reactions
(e .g.) malignant hyperthermia - Anaphylactoid reactions
(e .g.) histamine release on first exposure to the drug as with Cremaphor in “Saffan” - Allergic or hypersensitivity reactions:
- Drugs may act as haptens or as antigens
- Can occur with the active or the excipient
- Require previous exposure
- Severity does not correspond to the dose given
- Cross sensitivity may be seen to drugs with a related structure
(e. g.) A dog allergic to Penicillin G may also be allergic to amoxycillin
Type C Adverse Drug Reactions
Type C (Chronic) Reactions:
- Related to the cumulative dose and duration of administration
(e. g.) Hypothalamic pituitary adrenal axis suppression with long term corticosteroid administration
(e. g.) gastric bleeding after administering naproxen to a dog for 10 days (elimination half life = 72 hours)
Type D Adverse drug reactions
Type D (delayed) reactions:
- Time-related
- Usually dose-related
- Becomes apparent sometime after the use of the drug
- Uncommon
(e. g.) Carcinogenesis
Type E Adverse Drug Reactions:
Type E (end of use) Reactions: - Occurs soon after the withdrawal of the drug
(e. g.) Opioid withdrawal
(e. g.) Hypoadrenocorticism after withdrawal of long term corticosteroids
Type F Adverse Drug Reactions:
Type F (failure) Reactions:
- Unexpected failure of therapy
- Dose-related
- May be caused by drug interactions
(e. g.) A drug that induces liver enzymes may result in the increased rate of elimination of a drug metabolized by those enzymes