ACETYLATOR STATUS - urine or plasma

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Specimen: Laboratories differ in the drugs used to assess acetylator status - consult pathologist before commencing test. If the protocol specifies caffeine or a drug which the patient is already taking, a random specimen of urine is satisfactory. Otherwise, the patient is given a specified dose of a drug that undergoes acetylation (usually a sulphonamide) and urine is collected between five and six hours after the dose. For most drugs, the test can also be performed on plasma.

Method: Spectrophotometry, HPLC, GC.

Reference Interval: Depends on the drug. Slow acetylators usually excrete less than 60-80% of the drug in its acetylated form, whereas fast acetylators excrete more than 60-80% of the drug in its acetylated form.

Application: Assessment of the ability to perform acetylation of a potentially toxic drug which is detoxified by acetylation. Such drugs include sulphonamides (esp salicylazosulphapyridine), hydralazine, procainamide, isoniazid.

Interpretation: Slow acetylators are more likely to develop toxicity when given the drug.

Reference: Weber WW and Hein DW. Pharmacol Rev 1985; 37: 25-79.

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