The novel basic drug methcathinone has a pKa of 8. OF is collected from a driver stopped for possible DUI and is tested in a forensic toxicology laboratory. Assuming the blood is at physiological pH and the OF has a pH of 6.5, the concentration detected in the OF is likely to be _________ than the plasma concentration.

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Methcathinone has a pKa of 8, which means it is a weak base that will be mostly ionized at physiological pH (~7.4). When the pH is lowered to 6.5 in the OF sample, more of the drug will be in the lipid-soluble, non-ionized state, making it more easily detectable. This means that the concentration of methcathinone detected in the OF is likely to be higher than the plasma concentration.

The Novel Basic Drug Methcathinone Has a PKa of 8