Absence of pharmacokinetic interaction between digitoxin and quinidine in the dog

Clinical toxicology of cardiovascular drugs

Drugs used to treat cardiovascular diseases have low therapeutic indices, may produce the very pathophysiologic effects that it is hoped they will reverse, and are used commonly in aged animals with multisystemic diseases for which they are receiving other compounds. These factors predispose to undesirable drug reactions and interactions. It is difficult to determine, a priori, which animals will respond with profound toxic manifestations; therefore, resuscitative measures, including drugs and devices, must be available at all times, and the clinician must be schooled in their use. In particular, class IA antiarrhythmics, digitalis glycosides, and antineoplastic compounds, all used relatively frequently, have great potential for producing toxicosis. An important role of the clinician with regard to cardiovascular toxicology lies in providing consultation to both the pharmaceutical industry and governmental regulatory agencies. Because the worst aspects of cardiovascular toxicosis lie in electrical disturbances of the heart, and because electrocardiography is the best method for studying these electrical properties, the clinician and adviser to the pharmaceutical industry and the FDA must be well schooled in electrocardiography.

Drug interactions

Drug interactions are often the result of complex biochemical, physical, and kinetic factors and may not often be easily predicted or even recognized. Although this article has attempted to point out the more common mechanisms and results of drug interactions, the few interactions that have been documented in small animals are undoubtedly only the tip of the iceberg. For the safety of patients and for the highest quality of veterinary care, it is essential that the practitioner become thoroughly familiar with the actions and interactions of drugs used in his or her practice and realize the possible consequences of multiple drug therapies before adding another drug to a therapeutic regimen. From a therapeutics standpoint, the temptation to polypharmacy is great, but the adage "an ounce of prevention is worth a pound of cure" is especially appropriate when discussing drug therapy. The rational decision to use as few drugs as possible in any given situation is the route to safe and successful drug therapy.