Acetylator status

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.

This functional test is increasingly being replaced by pharmacogenetic tests.

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 (especially salicylazosulphapyridine), hydralazine, procainamide, isoniazid.

Interpretation:

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

Reference:

Pillans PI. Intern Med J 2001; 31: 476-478.