[Carbamazepine poisoning caused by confusing the drugs]

By error a pharmacist had dispensed to a 41-year-old woman Tegretal (carbamazepine; 400 mg retard tablets) instead of Trental (pentoxifylline; 400 mg retard dragées). Similarly, a 76-year-old woman had been prescribed carbamazepine-neuroxpharm (600 mg retard tablets) instead of piracetam-neuraxpharm (800 mg tablets) by her family doctor. Thirdly, a 79-year-old man was, as an in-patient, by error given by a nurse Tegretal, 400 mg retard tablets three times daily, presumably instead of 400 mg Trental retard. All 3 patients developed mild cerebellar symptoms. The two elder patients showed additionally wakefulness. After a fall the male in-patient, known to have a hemiparesis, also developed myoclonus in the limbs: computed tomography demonstrated a mild left temporal contusion.

Routine laboratory tests were unremarkable. All 3 patients had raised carbamazepine levels (12-13 micrograms/ml [normal range: 4-12 micrograms/ml]).

Because fast carbamazepine saturation had been done in those three patients by error, all of them showed symptoms of carbamazepine overdosage, but all symptoms fully regressed within a few days without specific treatment.

Adverse drug events are not rare in routine medical practice and should be thought of in the differential diagnosis of both in- and out-patients with unclear symptoms. In addition to careful history-taking and consideration of the clinical symptoms, toxicological screening can be of vital importance.