Renal clearance of endogenous creatinine and doxycycline in male volunteers

Renal clearance of endogenous creatinine and doxycycline was studied following on oral dose of 100 x 2 mg doxycycline in eight healthy adult male volunteers. Blood and urine samples were collected at predetermined time intervals after the drug administration and analyzed for creatinine and doxycycline concentration for the determination of their renal clearance. The average plus-minus SE pH value of blood was 7.81 plus-minus 0.030 and urine was 6.13 plus-minus 0.187. The average plus-minus SE values of creatinine in plasma and urine was 9.121 plus-minus 0.802 ug/mL and 435.80 plus-minus 144.92 ug/ml respectively. The average plus-minus SE value for creatinine doxycycline renal clearance were 1.109 plus-minus 0.297 ml/min/kg and 0.999 plus-minus 0.090 ml/min/kg body weight respectively. The mean plus-minus SE value for the clearance ratio was 0225 plus-minus 0.090. The studies indicated that the renal clearance of endogenous creatinine in male volunteers almost equal than the values given in literature and the renal clearance of doxycycline is slightly lower to the values given in the literature. It diffuses back and clearance decreases. With the increase in pH the drug becomes unionized hence excretion of drug increases as a result clearance of drug also increases. There is significant positive correlation between diuresis and doxycycline clearance Fig. 4. As the rate of urine flow increased rate of doxycycline clearance also increases and vice versa. However, at lower diuresis the renal clearance of doxycycline decreases because of back diffusion, compared to previous results. A positive correlation between diuresis and renal clearance of doxycycline was indicative of renal tubular back diffusion or reabsorption. There is trend of positive correlation (R2 = 0.139) between pH of urine and drug renal clearance. So pH of urine does not have any influence on the renal clearance of the drug.