Rhabdomyolysis caused by tocolytic therapy with oral ritodrine hydrochloride in a pregnant woman with placenta previa

Oral-ritodrine-hydrochloride-induced rhabdomyolysis is rare. We report a case of oral-ritodrine-hydrochloride-induced rhabdomyolysis in a pregnant woman with placenta previa without neuromuscular disorders. The patient was a 30-year-old, Japanese primigravida woman, who became pregnant spontaneously. At 23 gestational weeks, she was diagnosed as having placenta previa and prophylactic oral ritodrine hydrochloride (15 mg/day) was initiated. At 29 1/7 gestational weeks, she was referred to our hospital for perinatal management of placenta previa. Two days thereafter, vaginal bleeding accompanied by frequent uterine contractions occurred and she was admitted. On admission, laboratory tests revealed an abnormal increase of blood creatine kinase (CK) value of 7200 IU/L. CK-MB isoenzyme was 208 IU/L. Aspartate transaminase (163 IU/L), alanine transaminase (74 IU/L) and lactate dehydrogenase (536 IU/L) levels were also increased. The patient started to complain of extreme muscle pain in her upper and lower limbs and general weakness. The next day, laboratory tests revealed a tremendous increase of blood CK level of 87 300 IU/L, a blood myoglobin level of 11 200 ng/mL, and a urinary myoglobin level of 615 ng/mL. An emergency cesarean section was carried out. After delivery, the laboratory data improved gradually with the CK levels at 107 IU/L. If patients complain of muscular symptoms following oral ritodrine hydrochloride use, physicians should consider rhabdomyolysis.