Clinical and Forensic Drug Monitoring

Drug monitoring tends to be of two types 1) assays for specific therapeutic drug levels, closely related analogs, and preparation enhancers and 2) rapid, broad screening for the presence and overdosage detection of drugs of abuse. 

Theophylline, an asthma controller, has a very low safety/therapeutic ratio. One of the first clinical application for HPLC was to titrate theophylline levels in patient blood to avoid toxic overdoses. Blood levels can be controlled by assay at UV, 270 nm, on a C18 column in 7% An/water at pH 4.0 with phosphate buffer. 

Catecholamines, nerve transmitters monitored in brain and heart patients, are separated on C18 using octane sulfonate ion pairing in 6% An/water (pH 3) with added EDTA and phosphate. Detection can be at UV, 270 nm, or by electrochemical detection at +0.72 V for maximum sensitivity. Other tyrosine and tryptophan metabolite neurotransmitters such as serotonin, VMA, and HMA can be analyzed with ion pairing and EC detection. 

Anticonvulsants, used in controlling seizures, are analyzed on Ci8 columns at UV, 220 nm, eluting with 40% MeOFI/water. They are also common drugs of abuse and are monitored for in toxicology laboratories. 

Tricyclic antidepressants, major tranquillizers used in mental hospitals, are separated at UV, 254 nm, on Ci8 using 55% An/water at pH 5.5 with pentane sulfonate. Since these are very basic compounds, it is necessary to use hybrid or heavily end-capped columns and their separation benefits from organic modifiers, such as nonyl amine. 

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