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Published: 10 November 2010

Levamisole as a cocaine adulterant

Adulterants or ‘cutting agents’ are substances intentionally added to drugs, in particular to powdered drugs, to increase the sale value and economic benefit. They are distinguished from impurities, which are small quantities of unwanted substances from the synthetic process (King, 2009).

Cocaine, because of its high value, may be cut several times with one or more substances. These may be inert diluents (such as sugars and starch) that increase the volume of the drug. Pharmacologically active adulterants may also be used to enhance or mimic the drug’s effects or improve its appearance. This category includes analgesics (e.g. paracetamol), local anaesthetics (e.g. lidocaine), antihistamines (e.g. hydroxyzine), diltiazem and atropine (Meijers, 2007).

The use of levamisole (l-tetramisole) as a cocaine adulterant has been reported in the United States and Europe since 2004. Levamisole is used as an anti-parasitic agent in veterinary medicine and was formerly used in human medicine as an immunostimulant. When used over a long period and in high doses, it may cause adverse effects, of which agranulocytosis (1) is the most alarming.

Levamisole is not routinely identified in cocaine seizures, and is rarely quantified. The available information, however, indicates an increase in both the proportion of cocaine samples adulterated with levamisole and the concentration of levamisole in the drug. This led the European early-warning system (see New drugs and emerging trends) to issue a warning and to launch an additional data collection. A public health warning issued in the United States announced that over 7 % of cocaine seizures analysed in 2009 contained levamisole (2) and by the end of that year 20 confirmed or probable cases of agranulocytosis (with two fatalities) had been reported in the country. The number of cases in relation to the number of cocaine users appears, however, to be very low.

(1) Agranulocytosis is a haematological condition that can lead to rapidly-developing life threatening infections.

(2) SAMHSA news release.

King, L.A. (2009), Forensic chemistry of substance misuse: a guide to drug control, Royal Society of Chemistry, Cambridge.

Meijers, R. (2007), Toxicity of cocaine adulterants, Trimbos Instituut, Utrecht.

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Page last updated: Monday, 18 October 2010