A case of zaleplon overdose

To the Editor:

Zaleplon is a non-benzodiazepine hypnotic of the pyrazolopyrimidine class used for treating severe insomnia. We report a case of zaleplon overdose associated with blue-green discoloration of the mouth and lips, urine, and emesis.

A 24 year old woman was brought by a friend to the emergency department after having possibly ingested as many as 28 tablets of zaleplon. Her friend brought in empty blister-packs of zaleplon found in the patient´s car. The time of ingestion was undetermined but from her friend's account it was most likely more than 4 hours earlier. On arrival the patient was confused and sleepy. She looked pale and her mouth and lips were stained blue-green. Soon after arrival she vomited remarkably dark blue-green stomach contents. Cardiopulmonary examination was unremarkable and normal bowel sounds were present. Pupils were symmetric, isocoric and reactive to light. Though a complete neurological examination was difficult to perform initially due to her altered mental status, no salient abnormality was evident. Initial vital signs were pulse rate 99 beats/minute, blood pressure 85/65 mmHg, respiratory rate 18 breaths/minute, temperature 36.8ºC, pulseoximetry saturation 92% at room air. The patient was admitted to the observation unit of the emergency department for close monitoring. Her low blood pressure responded adequately to a 20 mL/kg bolus of normal saline. Gastric lavage and charcoal administration were withheld given the time interval. The patient was given 50% oxygen via Venturi mask maintaining 100% saturations. Chest radiography revealed no signs of pulmonary aspiration. The electrocardiogram showed sinus tachycardia. A blood test revealed only mild leukocytosis. Ethanol levels were undetectable. Her urine sample was strongly blue-green in color and a urine drug screen for opioids, benzodiazepines, cocaine, amphetamines, barbiturates, methadone and cannabinoids was negative. On admission the patient became restless, was confused and suffered visual hallucinations and intermittent myoclonia.

The next day the patient was alert and cooperative and a complete physical and neurological examination found nothing abnormal. She was then referred to a psychiatrist. She denied use of illicit drugs. She attributed her overdose to stress in personal relationships and work. She adamantly denied a suicidal motive and only desired to sleep profoundly for a while and so took her grandmother's sleeping pills.

Discussion

Zaleplon has proved useful in treatment of insomnia due to its rapid absorption and onset, low tolerance and short half life. Peak concentrations are reached within an hour and mean elimination half-life is also about an hour (1,2). Adverse clinical effects in therapeutic doses include mild or moderate headaches, dizziness, gastrointestinal symptoms, visual hallucinations, and depersonalisation (1,2,3). An exacerbation of these symptoms and decreased level of consciousness can occur in cases of overdose though abnormal behaviour and sleepwalking have also been reported (4).

The case presented is remarkable for the unusual finding of blue-green discoloration of lips, urine and emesis. To our knowledge these findings have been reported previously in two patients (5). In one of these cases a blue-green fluid was found after gastric lavage. Our patient had discoloration of both urine and emesis. The color is attributed to indigo carmine in the zaleplon capsules. This particular blue-greenish content of the emesis and the discolouration of urine could be an important sign of zaleplon overdose.