Background: The recent introduction of the depot somatostatin analogues octreotide LAR and lanreotide represent major advances in the medical treatment of acromegaly. However, it is uncertain whether the recommended dose intervals of 4 weeks and 10-14 days, respectively, are applicable to all patients.
Aims: To determine the optimum intervals between depot injections of either octreotide LAR and lanreotide for the suppression of serum GH and IGF-I in patients with acromegaly. Twenty-seven patients with acromegaly were randomly allocated to receive either three injections at 4 week intervals of octreotide LAR (n = 18) or five injections at 14 day intervals of lanreotide (n = 11); two patients participated in both arms. Prior to the first injection, at 4 and 6 weeks after the last injection of LAR, and at 10, 14 and 21 days after the last injection of lanreotide, serum mean GH and IGF-I levels were measured.
Results: In the LAR-treated group, at 4 and 6 weeks after the third injection 13 patients (72%) and 12 patients (67%), respectively, had a mean GH < 5 mU/l. IGF-I was normalized in 12 and 11 patients at these times. In the lanreotide-treated group, five (45%), four (36%) and three (27%) patients, respectively, had a GH < 5 mU/l at 10, 14 and 21 days after the last injection and eight, six and five patients had a normal serum IGF-I.
Conclusion: There is marked variability in individual patient responses to depot somatostatin analogues. The establishment of optimal drug intervals requires careful assessment. For octreotide LAR many patients may be as adequately controlled with 6 weekly injections as with 4 weekly injections. It is important to measure serum GH profiles at intervals after initiating therapy with these drugs to individualize doses for each patient and hence minimize cost.