Table 4.

Drugs and foods interfering with 5-HIAA assay

False negative results

Acetylsalicylic acid  Phenothiazines: chlorpromazine, promethazine  Imipramine and MAO-inhibitors  ACTH  Ethanol  MethylDOPA and hydrazine derivatives  Ketoacids  LevoDOPA  Isoniazid, methenamine, gentisic and homogentisic acid  Streptozotocin  Heparin

False positive results

Acetaminophen, naproxen, phenacetin  Caffeine, nicotine  Coumaric acid  Diazepam  Ephedrine  Fluorouracil, melphalan  Phenobarbital  Phentolamine, reserpine, guaifenesin, mephenesin  Methamphetamine,  Phenmetrazine  Methocarbamol  Mesalamine  Foods: bananas, avocados, kiwi, pineapples, peanuts, tomatoes, plums, eggplants, walnuts, pecans, coffee, tea, cocoa/chocolate, vanilla, sweets, and cookies (sugar and marmalade are allowed)