Direct and rapid determination of baclofen (Lioresal) and carisoprodol (Soma) in bovine serum by liquid chromatography-mass spectrometry

Baclofen (Lioresal), a lipophilic analogue of c-aminobutyric acid (GABA), and carisoprodol (Soma), a central nervous system depressant with an unknown mechanism of pharmacologic action, are categorized as muscle relaxants. Baclofen is used clinically in the management of spasticity and its sequelae secondary to severe chronic disorders such as multiple sclerosis and other types of spinal cord lesions. Carisoprodol is used for discomfort associated with acute and painful musculoskeletal conditions. Intoxication from these drugs occurs in both humans and animals necessitating a need for their detection in plasma/serum, tissue, and gastrointestinal contents samples. A sensitive and specific analytical method for detection and quantitation of these compounds using liquid chromatography with positive atmospheric pressure chemical ionization-mass spectrometry was developed. A rapid extraction procedure for both analytes from fortified bovine sera is described. Chromatographic separation was carried out on a C(18) reverse-phase column with a gradient elution of acetonitrile and 0.25% acetic acid. The effluent was directed to the mass spectrometer with fragmentation information for baclofen and carisoprodol obtained in a scan monitoring mode. Linear standard curves for baclofen and carisoprodol were constructed based on at least two corresponding extracted ions over a concentration range of 0.1-50 micro g/mL. The analysis of fortified sera samples demonstrates good accuracy and precision for the method with a limit of detection of 0.5 micro g/mL for carisoprodol (n = 3) and 1 micro g/mL for baclofen (n = 4) and a limit of quantitation of 2 micro g/mL for both compounds. Recoveries at the limit of quantitation were between 75 and 95% for both analytes, with a 4.8-9.3% range in standard deviation.