quinapril

angiotensin converting enzyme inhibitor prodrug

indications

chronic heart failure, especially mitral regurgitation

contra-indications

aortic stenosis, pregnancy

side effects

hypotension in overdose, mild hyperkalaemia

care

with frusemide - hypotension, renal damage, reduces uptake of tetracyclines

dose

dog & cat - 0.5mg/kg once daily

notes

not widely used in domestic animals

quinidine

class 1 antiarrhythmic

indications

supraventricular arrhythmias, traditionally atrial fibrillation

side effects

anorexia, vomiting, diarrhoea, tachycardia, ventricular fibrill-ation, allergy, laminitis, ataxia, nasal mucosal swelling

contra-indications

liver disease, myasthenia gravis, complete A-V block, intra-ventricular conduction defects, symptoms of digitalis toxicity

care

acid-base disorders, hypokalaemia, hypoxia, and renal or liver insufficiency

pharmacokinetics

Absorption orally nearly completely absorbed

Distribution 85% protein bound, displaces digoxin from skeletal muscle binding and reduces digoxin plasma clearance, resulting in higher plasma digoxin concentrations

Metabolism Half life in dog - 5-6 hrs, cat - 2 hours therefore useless for maintenance therapy. Some first pass effect and is metabolised by hydroxylation in the liver to some cardioactive and some inactive metabolites. Microsomal enzyme inducing drugs eg. anti-convulsants may decrease tl/2. Renal disease and heart failure may increase serum concentrations through decreased clearance

Elimination About 20% of a dose may be excreted unchanged in the urine within 24 hours of dosing. Acidic urine (pH<6) can increase renal excretion of quinidine.

dose

horse 20mg/kg po every 2 hours until AF goes or side effects start, max 60g

dogs 6 - 16 mg/kg po 3 - 4 times daily

interactions

increases digitalis plasma levels, increased chance of arrhythmias with diuretics which induce hypokalaemia, ie frusemide and thiazides.

notes

mainly used in horses because it is cheap enough to give horse size doses