Drug Interaction Report

MONITOR: The neuromuscular blocking effect of succinylcholine may be potentiated by chronic administration of estrogens or high-dose corticosteroids. Available data suggest that steroids may reduce plasma cholinesterase activity, resulting in decreased metabolic clearance of succinylcholine. There have been isolated case reports of patients treated with estrogen-containing products such as estradiol and diethylstilbestrol who experienced prolonged apnea or muscle paralysis following succinylcholine administration. Laboratory testing demonstrated reduced serum pseudocholinesterase activity in these patients. One study conducted in 33 women of childbearing age reported significantly reduced serum cholinesterase levels after one month of treatment with various oral contraceptives, with no further reductions after three months. Another 33 women in the same study who had been taking oral contraceptives for at least one year exhibited similarly reduced levels of serum cholinesterase.

MANAGEMENT: Patients receiving chronic therapy with estrogens or corticosteroids should be monitored for increased or prolonged neuromuscular blockade when succinylcholine is administered. A lower initial dosage of succinylcholine may be required.