Veterinary Pharmacology: Drug Use and Safety

Drugs

• A drug is a substance administered to diagnose, treat, prevent disease, relieve pain, or improve physiological function.

Over-the-Counter (OTC) Drugs

• These can be purchased without a prescription

Extra-Label Drug Use

• When a vet prescribes a drug for a use not specifically listed on its label.

Drug Compounding

• The process of combining or altering drugs to create a customized medication for a specific patient.

Duration of Treatment on Prescription Label

• Includes the drug name, quantity dispensed, route, frequency, and timeframe for administration.

Therapeutic Range

• The concentration of a drug in the body that produces a desired effect with minimal toxicity.

Loading Dose

• An initial higher amount to quickly reach the therapeutic range.

Low Margin of Safety

• This is when a drug's effective dose is close to its lethal dose.

High Margin of Safety

• This is when the Lethal dose is greater than the effective dose

Protein Binding

• This is when drug molecules bind to blood proteins like albumin, slowing distribution.

Ion Trapping

• This occurs when a drug becomes trapped in a body compartment due to pH differences.

Acetylcholine

• A neurotransmitter released at the neuromuscular junction to stimulate muscle contraction.

Pancuronium

• A neuromuscular blocker competes with acetylcholine for receptor sites.
• Requires a reversal agent to restore muscle function.

Positive Dromotropic Drugs

• Increase conduction of myocardial electrical impulse.
• Used to treat Heart Block.

Negative Dromotropic Drugs

• Decrease conduction of myocardial electrical impulse.
• Used to treat AV Block.

Positive Chronotropic Drugs

• Increase heart rate.
• Used to treat Bradycardia.

Negative Chronotropic Drugs

• Decrease heart rate.
• Used to treat Tachycardia.

Positive Inotropic Drugs

• These increase the force of myocardial contraction.
• They are used to treat congestive heart failure.

Negative Inotropic Drugs

• Decrease the force of myocardial contraction.
• Used to treat hypertension

Epinephrine (Cardiac Stimulant)

• Increases force and rate of contraction.
• Causes vasoconstriction to increase BP.
• Used to treat cardiac and respiration arrest.

Dopamine (Cardiac Stimulant)

• Increases BP and heart rate & contraction.
• Used to treat acute heart failure

Dobutamine (Cardiac Stimulant)

• Increases Heart Contraction.
• Used to treat cardiac depression with hypotension.

Digoxin & Digitoxin

• Increase strength of contraction and decrease heart rate.
• Used to treat CHF.
• Have a low therapeutic index.

Pimobendane - Inodilator

• Acts as a vasodilator.
• Used to treat CHF.

Class IA - Membrane stabilizers

• Procainamide and Quinidine drugs increase conduction time and used to treat Ventricular Arrythmias

Class IB - Membrane stabilizers

• Tocainide and Lidocaine drugs increase conduction time and used to treat Ventricular Tachycardia

Class II - Beta Adrenergic Blockers

• Propranolol and Atenolol decrease Automaticit
• Atenolol is used to treat Hypertension
• Propranolol is used to treat Ventricular Arrhythmias

Class III - Potassium Chanel blocker

• Sotolol, Amiodarone and Bretylium, Reduce Sinus Rate, treat Ventricular arrythmias

Class IV - Calcium Channel Blocker

• Diltiazem and Verapamil reduce spontaneous depolarization
• Used to treat Ventricular Tachycardia

Amlodipine

• Treats Hypertension and inhibit movement of Ca2+

Vasodilator

• Opens constricted blood vessels, making it easier for the heart to pump blood through them.

Arteriole Dilators

• Cause arteriolar smooth muscle relaxation, reducing afterload.

ACE Inhibitors

• These work by inhibiting the angiotensin-converting enzyme, leading to vasodilation and reduced cardiac afterload.

Acetylsalicylic Acid (Anticoagulant)

• Prevents clot formation by inhibiting thromboxane, a substance that makes platelets sticky.

EDTA (Anticoagulant)

• Chelates Ca2+, preventing clot formation.
• Used for blood tests or to chelate lead poison.

Heparin

• Stops conversion of prothrombin to thrombin.
• Used for blood tests or transfusion.

Hemostatic Drugs (Stop Bleeding)

• Silver Nitrate + Gel foam
• Vitamin K + Protamine Sulfate

Blood Enhancing Drugs

• Make red blood cells that produce in the kidney
• Iron
• Erythropoietin – Natural protein

Sympathetic Nervous System

• Responsible for the "fight or flight" response.

Parasympathetic Nervous System

• Acetylcholine is the primary neurotransmitter in this energy-saving division of the autonomic nervous system

Sympathomimetics (adrenergic)

• Mimic the effects of the sympathetic nervous system.

Sympatholytic (Adrenergic Blocking)

• Inhibit the effects of the sympathetic nervous system

Parasympathomimetic (Cholinergic)

• Mimic the effects of the Parasympathetic nervous system

Parasympatholytic (Anti Cholinergic)

• Inhibit the effects of the Parasympathetic Nervous system

Diazepam

• GABA is an inhibitory neurotransmitter

Pentobarbital

• A barbiturate often used in euthanasia solutions

Potassium bromide

• An anticonvulsant that requires blood level monitoring due to a low therapeutic index.
• Used in dogs only

Acepromazine

• Used for sedation and as an anti-emetic

Xylazine

• Provides sedation and is an anti-emetic.
• Can treat GI pain in horses.

Dexmedetomidine

• Used for sedation and analgesi

Doxapram

• Treats respiratory depression or arrest

Phenobarbital

• Drug blood levels 3-4 weeks post start or dose Athen q 6 mos
• Liver Function q 6 mos

Goblet Cells and Cilia

• Cellular structures that help trap and remove foreign material from the respiratory tract.

Antitussives

• Suppress non-productive coughs.

Anticholinergics

• Competitively block acetylcholine receptors to prevent bronchoconstriction

Acetylcysteine

• A mucolytic drug used to treat acetaminophen toxicity in cats and dogs

Guaifenesin

• Increases liquid secretion.
• Can cause muscle relaxation in horses.

Mucolytics vs. Expectorants

• Mucolytics are used for wet coughs when cilia cannot remove thick and sticky mucus.
• Expectorants increase liquid secretion to increase mucus fluid.

Phenylephrine

• It is a decongestant used to decrease blocking nasal passage
• Avoided in patients with hypertension or tachycardia because it increases blood pressure and heart rate.

Methylxanthine Bronchodilators

• Inhibit enzymes in bronchial smooth muscles that promote bronchoconstriction.

Terbutaline and Albuterol

• These two β2-adrenergic agonist drugs are commonly used for feline asthma