The effect of chronic cadmium exposure on the pharmacokinetics of theophylline and ciprofloxacin in rats

Cadmium has been associated with a number of adverse health effects but the impact of those effects on the pharmacokinetics of different drugs has not been investigated. Therefore, the pharmacokinetics of theophylline and ciprofloxacin were studied in cadmium-exposed and control rats (72 rats) following i.p. (6.5 mg/kg) and p.o. (10 mg/kg) administration, respectively. The third-generation offsprings of rats exposed to 100 μg/mL of cadmium chloride in drinking water were used in this study. Following 8 weeks of exposure, animals received the drugs as a single dose. Blood samples were withdrawn at different time-points and the plasma concentrations of both drugs were analyzed by HPLC. The pharmacokinetic parameters of theophylline and ciprofloxacin were altered significantly in the cadmium-exposed animals. For theophylline, a statistically significant increase (p<0.0001) in Cmax (69%) and AUC0−∞ (68%) of theophylline in the cadmium-exposed rats as compared to the control were observed. A corresponding significant (p<0.0001) reduction of 41% in clearance (CL/F) of theophylline was detected in the exposed group. Neither the half-life nor the mean residence time (MRT) showed any significant change due to the exposure to cadmium. For ciprofloxacin, no significant difference was seen in the Cmax of the exposed group as compared to the control animals. However, a delay in Tmax was observed in the exposed group (from 0.16(±0.003) to 0.37(±0.14) h). A small, but significant increase in t1/2 (p<0.05) was detected (1.74(±0.25) vs. 1.45(±0.12) h). A significant reduction (p<0.05) of CL/F from 30.54(±1.9) to 24.01(±3.81) mL/min/kg was seen in the treated group. The current investigation showed that chronic exposure to cadmium could have a very significant impact on altering the pharmacokinetic parameters of various drugs. Therefore, in cadmium-polluted areas, dose adjustments and drug monitoring, especially for drugs with a narrow therapeutic window, should be carried out.