Therefore, plasma lithium concentrations are not an accurate indicator of lithium toxicity in patients receiving concurrent methyldopa therapy. The most frequently reported adverse effect of methyldopa therapy is drowsiness. This usually occurs within the first 48-72 hours of administration and may subside with continued therapy. Larger doses produce sedation, decreased mental acuity, lapses of memory, and impaired ability to concentrate. Nightmares, vertigo, headache, weakness, and asthenia also have been reported, generally occurring during early treatment.
Orthostatic hypotension can occur with methyldopa administration.
Sinus bradycardia, worsening angina, and myocarditis have been reported, as well as congestive heart failure and carotid sinus hypersensitivity. Sodium and fluid retention can occur, producing edema, and can often be alleviated with concomitant thiazide diuretic therapy. Patients receiving methyldopa can develop a positive Coombs' test. This is usually not clinically important, but hemolysis with anemia has occurred on rare occasions, causing death in two patients. If hemolysis is present, methyldopa therapy should be discontinued.