Inhibition of the adverse reaction to diethylcarbamazine in Dirofilaria immitis-infected dogs by diazepam.

Eight dogs with a Dirofilaria immitis microfilaraemia predictive for a moderately severe post-diethylcarbamazine (DEC) reaction, and 6 dogs with a microfilarial density predictive for a severe, fatal or near-fatal, reaction were given 5 mg diazepam (Valium) by intramuscular injection followed, 30 minutes later, by an intramuscular injection of 5 mg/kg DEC. Diazepam completely, or almost completely, blocked the post-DEC adverse reaction in all dogs of both groups. However, 5 D. immitis-infected dogs given DEC immediately following the injection of diazepam all developed an adverse reaction of a degree of severity, as measured by clinical and haematological parameters, customary for their level of microfilaraemia.