Amelioration of decompression sickness in mice by pretreatment with cyproheptadine

Substances that stimulate smooth muscle have been previously implicated in the pathogenesis of decompression sickness. This concept was strongly supported by the demonstration that compounds that combine activities against histamine, bradykinin, and serotonin prevent or ameliorate decompression sickness. This communication deals with the prophylactic effect of cyproheptadine (Periactin), a drug exhibiting such pharmacologic properties. More than 500 obese mice were used. Experimental groups, subcutaneously injected with cyproheptadine (0.5-40 mg/kg) prior to compression, and corresponding control animals were simultaneously subjected to 75 psig air pressure for 6 h and then rapidly decompressed. Most control animals exhibited signs of decompression sickness (chokes, scratching, twitching, convulsions, paralysis) and died. Gross and histologic examination revealed gas bubbles in vessels and tissues, perivascular edema, and other changes. In cyproheptadine-treated animals the incidence and severity of clinical manifestations and pathologic alterations were reduced, and mortality was markedly decreased. Statistically significant results were obtained with doses of 2.5-10.0 mg/kg. The 5-mg/kg dose lowered mortality by 45.9%. These results support the proposed pathogenetic concept and suggest a potential preventive treatment for human subjects.