Two cases of agranulocytosis associated with cocaine use: is this phenomenon becoming more prevalent?

Levamisole in cocaine: unexpected news from an old acquaintance

Levamisole is a pharmaceutical with anthelminthic and immunomodulatory properties that was previously used in both animals and humans to treat inflammatory conditions and cancer. Levamisole has been identified as a cocaine adulterant in the United States since 2003. By 2009, the United States Drug Enforcement Administration (DEA) estimated that 69% of the cocaine seized contained levamisole. The first case reports of complications related to levamisole in cocaine users were published in 2009. The objectives of this article are to review the literature regarding the full spectrum of possible complications related to levamisole use for medical purposes, to review the current scope of levamisole-induced complications in cocaine users and to discuss the pharmacological properties that might explain the motivation behind the large-scale adulteration of cocaine with levamisole. Literature review revealed that significant complications were quickly reported when levamisole was used in inflammatory conditions. By 1976, several cases of leukopenia and agranulocytosis were reported. Recurrence with re-exposure was well described and agranulocytosis spontaneously reversed upon discontinuation of therapy. Vasculitis secondary to levamisole treatment was first reported in 1978 and mostly manifests as leukocytoclastic vasculitis, cutaneous necrotising vasculitis and thrombotic vasculopathy without vasculitis. These findings typically, but not invariably, involve the ear lobes. Discontinuation of levamisole therapy was again a critical part of the treatment. Various neurological side effects were described with levamisole therapy, the most concerning complication being multifocal inflammatory leukoencephalopathy (MIL). Literature review identified 203 unique cases of complications in cocaine users that can be attributed to levamisole adulteration. The two principal complications reported are haematological (140 cases of neutropenia) and dermatological (84 cases). Even though these complications can occur in isolation, many cases displayed both simultaneously. No formal case of leukoencephalopathy in the setting of cocaine use has been reported so far. A striking phenomenon is the apparent high level of recurrence (27.1%) of symptoms in cocaine users after re-exposure to cocaine that is presumably adulterated. The importance of accurately identifying levamisole-induced complications is therefore critical for symptomatic patients as discontinuation of exposure is fundamental and as a correct diagnosis prevents unnecessary and potentially dangerous use of other treatment modalities like powerful immunosuppressive therapy. Literature review suggests that levamisole might have the advantages of enhancing noradrenergic neurotransmission by inhibiting reuptake, by inhibiting MAO and/or COMT, by acting on ganglionic nicotinic receptors and by being partially metabolized into an amphetamine-like compound. It could also increase endogenous opioids and increase dopamine concentration in the cerebral reward pathway. These potential effects make levamisole an interesting choice as a cocaine adulterant. It seems unlikely that levamisole use as a cocaine adulterant will soon reach an end. More information is needed about the diagnosis and treatment of levamisole-induced complications, and the efforts of the medical and public health community is needed to face this challenging problem.

Aminorex poisoning in cocaine abusers

Levamisole is found in more than 80% of illicit cocaine seized within United States borders. Percentages are somewhat lower in Europe. In 2009, controlled in vivo studies demonstrated that horses metabolize levamisole to aminorex. Earlier this year our laboratory demonstrated that the same conversion occurs in man. Levamisole itself causes aplastic anemia and numerous reports have begun to appear in the literature, but the conversion of levamisole to aminorex is of much more concern. Aminorex ingestion was responsible for a five-year epidemic (1967-1972) of idiopathic pulmonary hypertension (IPH) confined to Switzerland, Austria, and Germany, the only countries where aminorex had been marketed as an anorectic. The incidence of IPH reverted to normal levels as soon as aminorex was withdrawn. In most cases onset of symptoms in IPH began after six to nine months of aminorex use, with average dosage ranges of 10 to 40 mg per day. The outcome was almost uniformly fatal. The conversion rate of levamisole to aminorex has not been established, but given the high daily intake of cocaine by many abusers, it seems likely that many of them will have ingested enough contaminated cocaine to ultimately cause IPH. Until the disease is well established, the symptoms of IHP are vague, and existing drug registries specifically exclude drug abusers, making it difficult to track these cases. This review is intended to draw attention to what may be a slowly emerging new epidemic.