PHARMACOKINETICS OF THE LONG‐ACTING SOMATOSTATIN ANALOGUE OCTREOTIDE (SMS 201‐995) IN ACROMEGALY

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Abstract
A single‐dose study was performed to examine the pharmacokinetics of subcutaneous octreotide in acromegalic patients and to investigate the relationship between growth hormone and the elimination half‐life of the drug. Fourteen acromegalic patients (six men and eight women; age range 35‐59 years) who had previously received conventional treatment were studied. Two subjects were on long‐term octreotide which had been discontinued 72 h before the study. Octreotide 100 μg was administered subcutaneously and plasma samples taken every 10 min for 1 h and then hourly for up to 8 h. Growth hormone was measured at 0, 2 and 8 h. Octreotide was rapidly absorbed with a mean (± SEM) t1/2abs of 5‐4 min (± 0.8) peaking at a mean plasma concentration of 3.4 nmo1/1 (± 0.2) in 27.4 min (± 3.7). The monoexponential elimination phase had a mean half‐life of 110 min (± 9.6). The apparent volume of distribution was 29.4 1 (± 1.9) and total clearance was 172 ml/min (± 10.4). These results were similar to those obtained in normal volunteers. There was no simple relationship between the level of growth hormone and the half‐life of octreotide. Growth hormone levels ranged from 2.5 to 34.0 mIU/1 but were only > 10 mIU/l in three subjects. Further studies of octreotide pharmacokinetics are needed in untreated patients with acromegaly with raised growth hormone levels.