AbstractA pilot bioavailability study was carried out to evaluate the drug interaction and influence of dioctyl sodium sulfosuccinate (DS) on the absorption/bioavailability of tetracycline. Three tetracycline products—a fast dissolving capsule, a slow dissolving capsule and a suspension, were used in the study. DS was administered (a) 30 minutes before tetracycline administration; and (b) on −3, −2 and −1 day in the evening before tetracyline administration. Frequent urine samples were collected up to 48 hours and analyzed by a microbiological method. Although not statistically significant in this small study, the results suggest that there is a reduction in tetracycline bioavailability due to DS. The indiscriminate use of surface active agents to increase the dissolution rate of solid oral dosage forms in the belief that the resulting increased dissolution improves product bioavailability must be que