Pharmacokinetics and drug interactions of herbal medicines: the effect of Garcinia kola and Carmellia sinensis on norfloxacin use in the treatment of urinary tract infections

People consume herbal products such as Garcinia kola seed (GKS) or Carmellia sinensis (tea) while on conventional or orthodox medication. Urinary tract infections are frequently treated using norfloxacin. This work investigated the clinical outcome of co-administration of norfloxacin, and either Garcinia kola seed (GKS) or Carmellia sinensis (tea) on the urinary clearance of E. coli using human volunteers. Three parallel groups were used for the study. The urinary excretion rate, urinary concentration-time profile, cumulative amount of drug excreted in urine and reciprocal urinary inhibitory titer (RUIT) were clinically determined for norfloxacin. Urine samples were collected at intervals (up to 24 h) from 3 groups (n = 4) of healthy volunteers (norfloxacin alone, norfloxacin and either GKS or tea) and used for the studies. The results indicated that both herbs reduced the peak excretion rate and peak urinary concentrations of norfloxacin. The percentage of norfloxacin recovered in the urine of subjects decreased from 2.3 ± 0.4% (without herb) to 2.0± 0.3 % (G. kola) and 1.5 ± 0.3% (C. sinensis) when herbs were administered concomitantly. Tea enhanced antibacterial activity at 1st and 3rd hours, while GKS maintained antibacterial activity much longer than the other groups. Although, all the groups had equal antibacterial potency at the 7th hour, only GKS could sustain it until the 10th hour. The highest bacteriostatic potency in urine was from subjects that consumed the antibiotics concomitantly with tea, suggesting that tea enhanced the potency of norfloxacin. The urinary concentration and hence bactericidal potency of norfloxacin was significantly influenced by tea and GKS, which may be beneficial in the treatment of urinary tract infections. Thus co-administration of tea and norfloxacin in the treatment of UTI may result in increased bacterial clearance, rapid recovery, and possibly some pharmacoeconomic advantagesKeywords: Drug-Herb Interactions, Pharmacokinetics, Urinary tract Infections, Pharmacotherapy, Synergism