OBJECTIVE Azithromycin (AZM) is widely used as a first-line treatment option for children with mycoplasma pneumonia. Although pharmacists perform medication counseling in the pediatric ward, children often experience vomiting as a result of oral AZM administration. Drugs that are administered rectally are generally considered to enter the circulation system without passing through the liver first. The aim of our study was to prepare an AZM suppository and investigate the pharmaceutical properties and well as pharmacokinetics of the rectal administration route in humans. METHODS Five healthy volunteers were enrolled in the study. All subjects provided written informed consent before participating in the study. Subjects were randomly assigned to either oral administration of oral AZM 500-mg tablet or rectal administration of 125-mg, 250-mg, or 500-mg AZM suppository. Blood samples for preparation of serum were collected predose as well as at 1, 2, 3, 4, 6, 12, and 24 hours following the first rectal dose. Serum concentrations of AZM were determined by high-performance liquid chromatography (HPLC) with electrochemical detection. CONCLUSIONS The bioavailability of the AZM suppository through rectal administration was 20.3% compared to oral administration. We hypothesize that the surface area where AZM is absorbed also affects the absorption by rectal administration. Although further investigation is necessary to improve the absorption of AZM by the rectum and to ensure safety in children, the AZM suppository may be an effective preparation in cases where oral administration is not tolerated.