To the Editor: The antinausea medication dimenhydrinate has been recognized as an over-the-counter drug of abuse for years. Dimenhydrinate can cause euphoria, induce pleasant visual and tactile hallucinations, and have anxiolytic effects (1). Patients suffering from schizophrenia may be at an increased risk of dimenhydrinate abuse because of the drug’s anticholinergic properties, which may alleviate the extrapyramidal side effects of their neuroleptics (2). While the effects of clozapine on reducing alcohol, nicotine, and even cocaine use have been described (3), we are not aware of published reports of clozapine decreasing dimenhydrinate use. We report two relevant cases.
Ms. A had multiple hospitalizations for schizophrenia from the age of 20. Her first dimenhydrinate abuse was at age 29. Ms. A abused dimenhydrinate repeatedly "to get high" during an 8-year stay in the hospital. At these times, she would be loud and aggressive, with extremely poor self-care. At times, Ms. A ingested 5000 mg of dimenhydrinate, and on more than 10 occasions, she had generalized seizures secondary to overdoses. She stated, "I was relying on [dimenhydrinate] to get me through the day." The ward staff believed that Ms. A’s dimenhydrinate abuse would eventually kill her.
We gave Ms. A clozapine when she was 35 years old. At a dose of 700 mg/day of clozapine, her blood level of the drug was 635 ng/ml. Ms. A reported a decreased urge to use dimenhydrinate while taking clozapine. She has since lived in the community, been free of seizures, and worked in a sheltered workshop for more than 3 years. Her dimenhydrinate use dropped to an average of 250 mg/day.
Mr. B explained his dimenhydrinate abuse of up to 3000 mg at a time by saying that it was a cheaper alternative to cocaine. Such ingestions were pleasant, as he reported that they made him "musical" and "creative." He was 36 years old when we first gave him a prescription for clozapine for his schizophrenia. It was difficult to achieve a therapeutic blood level of clozapine. We then gave him fluvoxamine to increase his clozapine blood level. At a clozapine dose of 700 mg/day and a fluvoxamine dose of 25 mg/day, his blood level of clozapine increased to 441 ng/ml. His cravings for dimenhydrinate markedly decreased when clozapine had reached a therapeutic level. Mr. B has been out of hospital for 1.5 years and has continued to use dimenhydrinate at a markedly reduced level.
These are the first reports to our knowledge of clozapine helping to reduce cravings for dimenhydrinate. While neither of these patients ceased to use dimenhydrinate completely, their use was greatly curtailed, thus decreasing problematic behavior and seizures. These changes coincided with therapeutic clozapine levels. More important, the patients themselves reported that clozapine decreased their cravings for dimenhydrinate. Indeed, as Ms. A stated, "Clozapine takes the place of [dimenhydrinate]."