Cardiovascular effects of diethylcarbamazine citrate.

1 The cardiovascular effects of the anthelmintic drug diethylcarbamazine citrate (DECC) were examined in cats anaesthetized with pentobarbitone. There were two quite distinct haemodynamic responses, an initial transient hypotension (occurring within 10 s of an intravenous injection) and a pronounced secondary hypertension which reached a peak 30-60 s after the injection. 2 Within 10 s of an intravenous injection of DECC (2.5 to 10 mg/kg) there was hypotension, bradycardia and there were reductions in left ventricular and carotid artery dP/dt max. These effects were most pronounced following injections into the pulmonary artery; they were not observed after bilateral vagotomy or after injections into the lumen of the left ventricle. It is suggested that DECC, like nicotine, stimulates vagal receptors in the pulmonary vascular bed. 3 The secondary phase was characterized by marked systemic and pulmonary hypertension, by contractions of the nictitating membrane and by increases in left ventricular dP/dt (at fixed isovolumic pressures), in cardiac output and in myocardial blood flow. All these effects were prevented, or markedly reduced, following the administration of hexamethonium or bethanidine and the pressor response was prevented by phentolamine. It is concluded that, in doses similar to those used in therapeutics, DECC stimulates sympathetic ganglia and releases noradrenaline. The relevance of this finding to the reported side effects of the drug are discussed. 4 DECC (5 or 10 mg/kg) significantly inhibited prostaglandin F2alpha-induced increases in peak inspiratory intra-tracheal pressure without modifying its pulmonary hypertensive effect. The possible relevance of this finding to the use of DECC in asthma is discussed.