Determination of the disappearance rate of iodine-125 labelled oils from the injection site after intramuscular and subcutaneous administration to pigs

The rate of disappearance of clinically used vegetable oils, Viscoleo, sesa me oil, castor oil and isopropyl myristate, from the injection site after i ntramuscular (i.m.) or subcutaneous (s.c.) administration to pigs were dete rmined by using a non-invasive gamma-scintigraphy method. All the oil vehic les were spiked with 2.5% (v/v) I-125-triolein and six injections of 1.9 ml were given to each of 12 pigs. No significant difference (ANOVA) in disapp earance rate of each individual oil vehicle from the different injection si tes was observed after administration of the oils: i.m. in the lower back, s.c. in the neck and s.c. in the mid-back. Likewise, no inter-individual di fference between the pigs was observed. The half-life of 14 days for Viscol eo was significantly smaller than those of the other oil vehicles (P < 0.00 01), i.e. 23, 20, 20 days for sesame oil, castor oil and isopropyl myristat e, respectively. Due to the spreading effect of the oils and reflux of the oils through the injection canal, the half-lives were calculated omitting t he data for the first sampling day. (C) 2001 Elsevier Science B.V. All righ ts reserved.