Influence of neutron activation factors on the physico-chemical properties of suppositories and their excipients

The effect of the neutron activation factors, i.e., admixture of samarium oxide (Sm2O3) and irradiation time, on the physico-chemical properties of the raw materials and the in vitro dissolution and disintegration of hydrophilic and lipophilic suppositories was investigated. It was possible to expose the pure bases and the model drugs (5-aminosalicylic acid [5-ASA] and ropivacaine hydrochloride) to 1 min of neutron irradiation in a flux of 1.1.1013 n cm-2s-1. The dissolution and disintegration of the corresponding suppositories showed that the physico-chemical properties and the fraction of incorporated drug together with the lipophilic/hydrophilic nature of the base were important factors. Sm2O3 increased the disintegration time of hydrophilic suppositories containing 5-ASA, while the dissolution of both drugs from these formulations remained unchanged. Sm2O3 did not alter the disintegration time of the lipophilic formulations, but it reduced the dissolution of both drugs from these suppositories. Irradiation induced different behaviour in the different bases.