VPT 311: General and Systemic Veterinary Pharmacology (2+1)

ACTIONS OF CALCIUM-CHANNEL BLOCKERS

• Most clinical ventricular arrhythmias are neither prevented nor suppressed by calcium-channel blockers
• Calcium-channel blockers are useful in treating arrhythmias involving re-entry within the AV node and in the rare forms of monomorphic ventricular tachycardia seen in patients with structurally normal myocardium
• Many of the calcium-channel blockers also have the ability to block sodium channels, probably due to the similarity in their amino acid sequences (sequence homology)
• Calcium-channel blockade is enhanced by verapamil (and to a lesser extent by diltiazem) as the frequency of depolarization is increased

Diltiazem

• For SVTs ,hypertension
• Dose: Dogs 0.125-0.35mg/kg i.v, chronic management- 0.5-1.5mg/kg p.o q8h
• Cats – 0.5-1mg/kg p.o
• Ferrets – ( hypertrophic cardiomyopathy)- 2-7.5mg/kg p.o twice daily
• V erapamil-
• Dose: Dogs – 0.05mg/kg i.v slowly, repeat every 5 minutes oral- 0.5-2mg/kg.q.8h