Anticoagulants (oral): The activity of oral anticoagulants may be potentiated by
anti-vitamin-K activity attributed to methimazole.
ß-adrenergic blocking agents: Hyperthyroidism may cause an increased clearance of
beta ratio. A dose reduction of beta-adrenergic blockers may be needed when a hyperthyroid patient becomes
Digitalis glycosides: Serum digitalis levels may be increased when hyperthyroid patients
on a stable digitalis glycoside regimen become euthyroid; reduced dosage of digitalis glycosides may be required.
Theophylline: Theophylline clearance may decrease when hyperthyroid patients on a stable
theophylline regimen become euthyroid; a reduced dose of theophylline may be needed.