Introduction: Nitrofurantoin (NFT) is abroad spectrum bactericidal antibiotic. The bioavailability of NFT is affected by many factors. Samafurantin® tablets containing 50 mg NFT were manufactured by Samarra drug industry. Urinary excretion studies were employed since; the urinary tract is the main site of NFT action and excretion. Objective: The objective of the study was to investigate the effect of Uricol® and food on secondary pharmacokinetic parameters of Samafurantin® tablets with different doses by applying urinary data. Methods: Twelve healthy male volunteers participated in this study. Urine samples were collected from each volunteer after overnight fasting at a specified time intervals which considered as a blank sample for measuring urine pH of urine. After that, volunteers were randomly divided into two groups (G1 and G2) each of six. Group 1 was administered 100 mg of NFT (Two tablets of 50 mg Samafurantin®) while, G2 was administered 200 mg of NFT (Four tablets of 50 mg Samafurantin®) as a single oral dose. Both groups administered the dose on an empty stomach (fasting), along with one Uricol® of 5 g sachet on fasting, and on full stomach after eating a standard breakfast after 1-week washout period between each experiment and another. For each experiment, urine samples were collected from each volunteer from 0.25 to 7 h post dosing. In addition, the volume of each void urine sample was measured. Results: Both groups (G1 and G2) showed only slight differences in the pH of urine after administration of Samafurantin® as compared with that of the blank. While, the pH of urine for both groups was higher after administration of Samafurantin® tablets along with Uricol® 5 g. In both groups, each of Uricol® and food exhibited no significant differences (P < 0.05) in secondary pharmacokinetic parameters of NFT; the rate constant of elimination (Kel) and absorption (Ka) and consequently their half-life (t0.5 el and t0.5 abs) as long as the drug followed first-order kinetics. While significant differences (P < 0.05) were observed for maximum excretion rate (ExRmax), cumulative amount excreted in urine (CAe) and CAe as percentage of the dose. This could be attributed to the pH-change of urine by Uricol® which alkalinized the urinary and kidney tract or delaying gastric emptying by food. Same observations were attained when comparing G1 with G2 after administration of NFT on fasting. Conclusions: Administration of Samafurantin® tablets at higher doses, along with Uricol® or with food increases secondary pharmacokinetic parameters related to the rate and extent of absorption and elimination without significant changes in their corresponding rate constants and half-lives. © 2018 Drug Invention Today.
