Complete atrioventricular block due to overdose of pregabalin

Pregabalin, a synthetic derivate of the inhibitory neurotransmitter gamma-aminobutyric acid, shows antiepileptic, analgesic, anticonvulsant, anxiolytic, and sleep-modulating activities. The major advantage of pregabalin is its relative reliability, easy use, high tolerance, and lack of negative interaction with other drugs. A 65-year-old woman with medical histories of diabetes mellitus, lumbar spondylosis, diabetic nephropathy, chronic renal failure, and anemia of chronic disease was admitted with the complaint of dizziness and syncope. She had been taking pregabalin 300 mg daily for 8 months. Electrocardiogram revealed complete atrioventricular (AV) block and right bundle-brunch block with a heart rate of 39 per minute. Her creatinine was 1.8 mg/dL, and creatinine clearance was 50 mL/min. Pregabalin treatment was discontinued. Four days later, the complete AV block resolved spontaneously to Mobitz type II block and to sinus rhythm with right bundle-brunch block on the seventh day. To our knowledge, this is the first case of complete AV block associated with pregabalin. We believe that AV block occurred as a result of pregabalin's effect on L-type Ca++ channels in the heart. Pregabalin's different effects on electrocardiogram and on the heart in different individuals may have an association with the patterns of distribution of the L-type calcium channels in myocardium.