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

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Abstract
OBJECTIVE: To compare the effects of monthly intramuscular injections of a long acting preparation of octreotide, Sandostatin LAR, with multiple daily subcutaneous injections of octreotide and to study the interrelationships between 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 other GH modifying drug therapy; on subcutaneous octreotide (200–600 μg daily in divided doses for six weeks); and 28 days after the second of two injections of Sandostatin LAR (20 mg by intra‐muscular injection) administered 28 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 any adverse effect and all completed the study uneventfully. Mean GH off treatment was 10.1 ± 3.0 μg/l falling equally significantly (P < 0.05) during therapy with subcutaneous octreotide to 3.0 ± 0.7 μg/l and Sandostatin LAR to 2.8 ± 0.7 μg/l. Fasting 0900 h GH was significantly reduced (P < 0.05) on Sandostatin LAR (3.0 ± 0.7 μg/l) compared with subcutaneous octreotide (5.1 ± 1.2 μg/l). Mean total IGF‐1 off treatment was 658.6 ± 56.1 μg/l and was reduced to a comparable extent with subcutaneous octreotide and Sandostatin LAR (466.0 ± 59.7 and 448.6 ± 59.5 μg/l respectively; both P < 0.05). Free IGF‐1 off treatment was 3.1 ± 0.6 μg/l and was reduced equally by subcutaneous octreotide and Sandostatin LAR (1.2 ± 0.2 and 1.2 ± 0.2 μg/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 μg/l; P < 0.05). Twenty‐four hour urinary GH excretion was reduced to a comparable extent with both therapies. Highly significant positive correlations were found between mean 24 h GH levels 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 total IGF‐1 and IGFBP‐3 although significant showed less powerful correlations.CONCLUSIONS: These results suggest that Sandostatin LAR is well tolerated and as effective as subcutaneous octreotide. In addition, urinary growth hormone and serum free IGF‐1 may prove valuable for outpatient follow‐up of acromegalic patients, as both correlate well with mean 24 h serum growth hormone levels.

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