The aim of the present study tvas to determine, using ibuprofen as a m
odel drug, whether hard gelatin capsules were of value as rectal dosag
e forms in man. The effects of training in administration of the capsu
les and use of liquid paraffin as a glidant were also studied. The inf
luences of different diluents in the capsule, i.e., lactose, dicalcium
phosphate and hydroaxypropyl methylcellulose, on the bioavailability
of ibuprofen were determined The results showed that ibuprofen is adeq
uately absorbed after rectal administration via hard gelatin capsules.
Training in administration and use of a glidant to facilitate rectal
administration nonetheless played an important role. The type of dilue
nt used markedly affected bioavailability. Capsules containing lactose
behaved like immediate release formulations. Those containing hydroxy
propyl methylcellulose behaved like prolonged release products.