Cocaine adulteration with the anthelminthic tetramisole (levamisole/dexamisole): Long-term monitoring of its intake by chiral LC-MS/MS analysis of cocaine-positive hair samples

Molecular Insights and Clinical Outcomes of Drugs of Abuse Adulteration: New Trends and New Psychoactive Substances

Adulteration is a well-known practice of drug manufacturers at different stages of drug production. The intentional addition of active ingredients to adulterate the primary drug may enhance or mask pharmacological effects or may produce more potent drugs to increase the number of available doses and the dealer's profit. Adulterants found in different drugs change over time in response to different factors. A systematic literature search in PubMed and Scopus databases and official international organizations' websites according to PRISMA guidelines was performed. A total of 724 studies were initially screened, with 145 articles from PubMed and 462 from Scopus excluded according to the criteria described in the Method Section. The remaining 117 records were further assessed for eligibility to exclude articles without sufficient data. Finally, 79 studies were classified as "non-biological" (n = 35) or "biological" (n = 35 case reports; n = 9 case series) according to the samples investigated. Although the seized samples analyses revealed the presence of well-established adulterants such as levamisole for cocaine or paracetamol/acetaminophen for heroin, the reported data disclosed new adulteration practices, such as the use of NPS as cutting agents for classic drugs of abuse and other NPS. For example, heroin adulterated with synthetic cannabinoids or cocaine adulterated with fentanyl/fentalogues raised particular concern. Notably, adulterants play a role in some adverse effects commonly associated with the primary drug, such as levamisole-adulterated cocaine that may induce vasculitis via an autoimmune process. It is essential to constantly monitor adulterants due to their changing availability that may threaten drug consumers' health.

Separation and Determination of the Enantiomeric Levamisole and Dexamisole in Equine Plasma Samples Using Chiral Polysaccharide Column/ LC-MS/MS

Background:

Drug Enforcement Administration confirmed that many manufacturers began adding tetramisole or its individual isomers to cocaine as an adulterant, and believed that tetramisole may augment cocaine’s effects. In recent times, there is an increasing trend in the usage of tetramisole and its individual enantiomer in race sports especially in horse and camel races. So it’s is very much required to confirm the stereochemistry of this illicit drug in the routine race day samples coming to the anti-doping labs in order to avoid legal arguments and challenges to the analytical findings.

Methods:

The aim of the study was to develop a simple, rapid and accurate method for the chiral separation and determination of enantiomeric mixtures of levamisole and dexamisole using Thermo Q-Exactive High-Resolution Mass Spectrometer. In order to evaluate the suitability of the method for determining the enantiomeric purity of tetramisole, validation studies were also carried out by using equine plasma.

Results:

The enantio-separation was achieved using the Lux i-cellulose-5 column. Isocratic flow was used with a 1:1 mixture of mobile phase A (10 mM ammonium acetate in water) and mobile phase B (acetonitrile), at a flow rate of 0.6 mL/min. The run time was 8.0 min, and the column temperature was 50°C. Dexamisole eluted at 5.94 min, and levamisole eluted at 6.62 min, giving the R-value of 1.50. The obtained inter-day precisions of dexamisole, levamisole were 3.16% and 2.85%, respectively. The accuracy of dexamisole was in the range of 97.78 to 102.44%, and that for levamisole was 99.16 to 102.82%. The limit of quantification value for both isomers in this method was 0.1 ng/ mL. The method was linear in the range of 0 to 50 ng/mL.

Conclusion:

Chromatographic separation was achieved using the polysaccharide cellulose chiral column, and the reverse-phase separation approach was found to have the highest potential for successful chiral resolution in LC-MS. Linearity, precision, accuracy, detection limit, recovery, and the matrix effect in equine plasma were determined. Under the optimized conditions, the validated method can be applied for the identification and detection of the tetramisole enantiomers in different sources of illicit drugs of abuse.