Hypersensitivity reactions to trimetrexate.

Trimetrexate is a nonclassical antifol currently being tested for efficacy in cancer patients and as an antiparasitic agent against Pneumocystis carinii pneumonia in AIDS patients. We have now received the first reports of hypersensitivity reactions in Phase II cancer trials. Two types of reactions were noted. The most severe reaction, immediate hypotension with loss of consciousness, occurred in only one patient. Four other patients exhibited an immediate systemic effect with one or more of the following symptoms: facial flushing, fever, shaking, pruritus, bronchospasm, periorbital edema, and difficulty in swallowing. Immediate hypersensitivity should now be considered a known side effect of trimetrexate therapy, occurring in less than 2% of patients.