Comparison of monthly intramuscular injections of Sandostatin LAR with multiple subcutaneous injections of octreotide in the treatment of acromegaly;effects on growth hormone and other markers of growth hormone secretion

OBJECTIVE To compare the effects of monthly intramuscular injections of a l ong acting preparation of octreotide, Sandostatin LAR, with multiple daily subcutaneous injections of octreotide and to study the interrelationships b etween mean 24 h growth hormone profile, serum total and free IGF-1 levels, 24 h urinary growth hormone levels and serum IGFBP-3, DESIGN Patients were assessed by 24 h GH profile off octreotide or any othe r GH modifying drug therapy; on subcutaneous octreotide (200-600 mu g daily in divided doses for six weeks); and 28 days after the second of two injec tions of Sandostatin LAR (20 mg by intra-muscular injection) administered 2 8 days apart. Serum total and free IGF-1, serum IGFBP-3 and 24 h urinary GH were also measured on each occasion, RESULTS Sandostatin LAR was well tolerated. None of the patients reported a ny adverse effect and all completed the study uneventfully. Mean GH off tre atment was 10.1 +/- 3.0 mu g/l falling equally significantly (P < 0.05) dur ing therapy with subcutaneous octreotide to 3.0 +/- 0.7 mu g/l and Sandosta tin LAR to 2.8 +/- 0.7 mu g/l. Fasting 0900 h GH was significantly reduced (P < 0.05) on Sandostatin LAR (3.0 +/- 0.7 mu g/l) compared with subcutaneo us octreotide (5.1 +/- 1.2 mu g/l). Mean total IGF-1 off treatment was 658. 6 +/- 56.1 mu g/l and was reduced to a comparable extent with subcutaneous octreotide and Sandostatin LAR (466.0 +/- 59.7 and 448.6 +/- 59.5 mu g/l re spectively; both P < 0.05). Free IGF-1 off treatment was 3.1 +/- 0.6 mu g/l and was reduced equally by subcutaneous octreotide and Sandostatin LAR (1. 2 +/- 0.2 and 1.2 +/- 0.2 mu g/l; both P < 0.05). IGFBP-3 was reduced to a greater extent during Sandostatin LAR than during subcutaneous octreotide ( 4518.2 +/- 247.3 vs 5132.8 +/- 280.7 mu g/l; P < 0.05). Twenty-four hour ur inary GH excretion was reduced to a comparable extent with both therapies, Highly significant positive correlations were found between mean 24 h GH le vels and free IGF-1 (r = 0.66, P < 0.0001) and 24 h urinary GH excretion (r = 0.94, P < 0.0001). The relationships between mean 24 h GH levels and tot al IGF-1 and IGFBP-3 although significant showed less powerful correlations , CONCLUSIONS These results suggest that Sandostatin LAR is well tolerated an d as effective as subcutaneous octreotide, In addition, urinary growth horm one and serum free IGF-1 may prove valuable for outpatient follow-up of acr omegalic patients, as both correlate well with mean 24h serum growth hormon e levels.