Carbamazepine induced osteomalacia: letter to the editor.

A 45 year-old woman with epilepsy who was treated with Carbamazepine (CBZ) 600 mg/daily for six years was seen at the neurology outpatient clinic with the complaints of back pain, weakness, fatigue, dizziness and recurrence of seizures during the last 2 months while she had been seizure free during the previous 4 years. She had been receiving no other medications. Detailed dietary and environmental (sun exposure) history did not suggest any risk factor for osteomalacia. Examinations of skin, eyes, respiratory, cardiovascular, gastrointestinal and neurological systems were all normal except for pain located bilaterally on the fifth and sixth thoracic rib areas by palpation. In laboratory examinations, thyroid hormones, complete blood cell count and erythrocyte sedimentation rate were normal. Her CBZ blood level was also in normal range : 29.75 mmol/L (N : 17-43 mmol/L). Biochemical analysis of the serum revealed. Alkaline phosphates (ALP) : 11.55 μkat/L (N : 0-4.5 μkat/L), calcium : 2 mmol/L (N : 2.202.55 mmol/L), phosphorus ; 0.61 mmol/L (N : 0.87-1.45 mmol/L), 25 (OH) D3 : 16.25 nmol/L (N : 25-110 nmol/L), Parathormone (PTH) : 395 ng/L (N : 10-65 ng/L). Serum calcitonin : 22 ng/L (N : 0-50 ng/L) and the urinary calcium excretion in 24-hours urine was 11.75 mmol/L (N : 12.5-75 mmol/L). ALP isoenzymes showed increased bone isoenzyme activity. 99m Tc-MDP bone scintigraphy of the patient showed focal regions of increased uptake at the ribs, bilateral humerus, proximal metaphysis and the left femur (Fig. 1). The patient was diagnosed with anticonvulsantinduced osteomalacia. The Naranjo probability score (3) for the adverse drug reactions (+7) was suggestive for this diagnosis. Since, epileptic attacks of the patient were not under control, antiepileptic treatment was continued. Calcitriol (1,25-dihydroxyvitamin D3) : 0.5 mcg/daily and calcium (elementary calcium) : 2 g/daily supplementations were initiated for the treatment of osteomalacia. Serum ALP and calcium concentration were monitored every each month during five months. At the end of this period, these critical bioCarbamazepine induced osteomalacia : Letter to the editor