Experimental studies on the acute cardiovascular toxicity of formalin and its antidotal treatment

Rats anesthetized with pentobarbital and ventilated artificially were infused with 0.01 ml formalin (= 0.12 mmol formaldehyde)/kg.min. They exhibited a sharp decline of arterial blood pressure, heart rate and peripheral resistance and a slower one of cardiac output and died after 59.9 +/- 6.0 min of infusion. Sinus bradycardia and, in some cases, AV-arrhythmia occurred in the ECG. The additional infusion with cysteine attenuated the cardiovascular failure and more than doubled the survival time of formalin-infused rats. Infusion of N-acetylcysteine or correction of formalin-induced metabolic acidosis with sodium bicarbonate, on the other hand, did not exert antidotal activity. On isolated rat atria in vitro, formalin decreased the rate and the contractility and cysteine antagonized these effects of formalin. In conclusion, the severe and often lethal incidents observed following the therapeutic administration of formalin are due to the cardiovascular-depressive activity of formaldehyde and may be antagonized by cysteine.