Antiepileptic drug poisoning: Three-year experience

Antiepileptic drugs, which are also called anticonvulsants, are used in the therapy and prophylaxis of epileptic seizures. The purpose of this paper was to investigate the relevant epidemiological data and to determine which of these drugs was the most frequent cause of intoxication. Another purpose of this study was to determine the neurological, cardiac, and biochemical problems caused by antiepileptics.

This retrospective study included 95 consecutive patients under 18 years of age with antiepileptic intoxication, presenting to and being followed-up in, the Toxicology Unit between January 2010 and February 2013. The data were obtained by screening the patient files.

Of the cases, 67 (70.5%) were self-poisoned by first generation antiepileptics (FGAEs) and 28 (29.5%) by second generation antiepileptics (SGAEs). The Glasgow Coma Scale (GCS) scores and the serum lactate levels of the patients poisoned by FGAEs and SGAEs on admission to emergency department were 15 (25th: 12; 75th: 15; 95th: 15; IQR: 3) and 1.9 (25th: 1.4; 75th: 3.1; 95th: 5.6; IQR: 1.7), and 15 (25th: 14.3; 75th: 15; 95th: 15; IQR: 0.75) and 1.07 (25th: 0.9; 75th: 1.6; 95th: 5.5; IQR: 0.71), respectively. The serum lactate levels of patients poisoned by FGAEs were significantly higher (p < 0.001). Among the cases poisoned by carbamazepine, the most frequent cause of intoxication, the GCS score was significantly lower and serum lactate level was significantly higher in the group with high serum levels of carbamazepine (p = 0.004 and p < 0.001, respectively). In cases poisoned by valproic acid (VPA), the second frequent cause of intoxication, there was neither a significant association between the serum VPA level and the GCS score, nor between the serum lactate level and the systolic blood pressure (p = 0.470, p = 0.897, and p = 0.088, respectively). However, there was a positive correlation between the serum VPA level and the serum ammonia level (kk = 0.742, p < 0.001).

First generation antiepileptics are more toxic than SGAEs. In patients with serum carbamazepine level, particularly those over 30 mg/L, serious disorders of consciousness, cardiovascular toxicity, and metabolic disorders may occur. In VPA intoxication, there is a positive correlation between the serum VPA levels and ammonia levels. On account of this finding, one should be more careful about hyperammonemic hepatic encephalopathy as the serum VPA level rises.