In a court-mandated drug screening programme, a habitual heavy marijuana smoker must declare how long cannabinoids remain detectable in his urine after last use, compared with an occasional user. The correct statement is:

• A Detection time depends only on dose, not on pattern of use
• B Chronic users clear the drug faster due to enzyme induction
• C Both occasional and chronic users test positive for exactly 48 hours
• D Occasional users test positive for 1 to 3 days; chronic heavy users may test positive for up to 3 to 4 weeks or longer ✓

Explanation

Delta-9-tetrahydrocannabinol is highly lipophilic and accumulates in adipose tissue, from which it and its metabolites are slowly released. In occasional users, urine immunoassays detect the carboxy metabolite for about 1 to 3 days, whereas in chronic heavy users detection extends to 3 to 4 weeks and occasionally longer. Enzyme induction cannot offset this large depot effect, so clearance is slower, not faster.

Reference: Katzung's Basic and Clinical Pharmacology, 15th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.