One hundred and three acromegalic patients from 14 medical centers were enrolled in this study to determine the efficacy and safety of the somatostatin analog, octreotide acetate, during long term treatment. Seventy percent of the patients had undergone previous surgery or radiation treatment. Octreotide was initiated at a dose of 100 micrograms, sc, every 8 h and gradually increased to a maximum of 1500 micrograms daily depending upon the individual patient's clinical and biochemical response [GH and insulin-like growth factor I (IGF-I) reduction]. The mean duration of treatment was 24 months (range, 3-30 months). However, most patients were treated for a mean of 30 months, because this study took place after an initial 6-month study previously reported. Mean serum GH fell from 30.9 micrograms/L (range, 2.7-350) to 5.7 micrograms/L (range, 0.6-59) at the 3 months visit and remained suppressed (P < 0.001). Plasma IGF-I concentrations were also significantly reduced and remained in the normal range for at least half of the treatment visits in 56 of 87 patients (64%) treated for 12-30 months. Patients with higher initial GH concentrations were less likely to normalize IGF-I concentrations during treatment (P < 0.001). There was no evidence of drug tachyphylaxis in those patients who continued taking stable doses of medication. With some exceptions, dose increments above 800 micrograms daily in 31 patients did not provide additional benefit in terms of GH and IGF-I reduction. Headache, excessive perspiration, fatigue, and joint pain were ameliorated in 83-95% of patients. Mean finger circumference was decreased significantly at the 12 month visit (P< 0.05). The most common adverse events reported were diarrhea, abdominal discomfort, loose stools, and nausea; these symptoms usually disappeared within 3 months of treatment. Five patients discontinued octreotide because of adverse events. Of 102 patients with normal baseline ultrasound examinations of the gallbladder, 24 patients (23.5%) developed gallstones (usually during the first year of treatment), and 21 patients developed sludge alone. Gallstone formation was not related to the dose of octreotide. Most patients with cholelithiasis were asymptomatic, and none developed cholecystitis. These observations suggest that octreotide is a valuable long term medical treatment for acromegaly.

Octreotide effectively decreased GH and IGF-1 concentrations in 53% and 68% of patients, respectively. The higher dose resulted in increased frequency of tumor shrinkage but added no biochemical or clinical benefit.

No abstract

The adverse gastrointestinal effects of octreotide, a synthetic analog of somatostatin, have not been fully elucidated. Low-dose octreotide frequently causes adverse gastrointestinal symptoms in normal individuals. We investigated the adverse gastrointestinal effects of high-dose octreotide, which is required for the normalization of growth hormone hypersecretion in some patients with acromegaly. Patients with acromegaly (N = 8) were treated with octreotide, 450 micrograms/day, then 1500 micrograms/day for two months at each dosage. Carbohydrate absorption was assessed using the D-xylose test, and fat absorption using fecal fat excretion and serum carotene concentrations, at baseline, at each dosage of octreotide, and after one month of washout. Ultrasonography was used to monitor for cholelithiasis. Growth hormone and insulin-like growth factor-I concentrations were significantly suppressed at both dosages. Adverse gastrointestinal symptoms were mild and transient. D-Xylose absorption remained normal at each dosage and after one month of washout. Fecal fat excretion increased from 7 +/- 2 to 12 +/- 2 g/24 hr (P < 0.05) after the higher dosage and resumed baseline levels after the washout. Mean fasting serum carotene levels remained normal, and carotene loading test (15,000 units three times a day for three days) was unreliable in identifying patients with high fecal fat. No new cholelithiasis was detected by ultrasonography. One of two patients with preexisting cholelithiasis developed biliary colic several days after the treatment period. Although steatorrhea was common, small intestinal absorptive capacity was otherwise unchanged by four months of high-dose octreotide treatment, which significantly suppressed growth hormone secretion in acromegalic patients.