OCTREOTIDE ACETATE

OCTREOTIDE ACETATE — octreotide acetate injection, solution
USV North America Inc.

DESCRIPTION

Octreotide Acetate Injection, a cyclic octapeptide prepared as a clear, colorless sterile solution of octreotide, acetate salt, in a buffered acetic acid solution for administration by deep subcutaneous (intrafat) or intravenous injection. Octreotide acetate, USP known chemically as D-phenylalanyl-L-cysteinyl-L-phenylalanyl-D-tryptophyl-L-lysyl-L-threonyl-N -[(1R ,2R)-2-hydroxy-1-(hydroxyl methyl)propyl]-L-cysteinamide cyclic (2→7)-disulfide acetate (salt), is a long-acting octapeptide with pharmacologic actions mimicking those of the natural hormone somatostatin.
Octreotide Acetate Injection is available as sterile 1 mL single-dose vials in 3 strengths, each mL containing 50 mcg, 100 mcg, or 500 mcg of octreotide acetate, USP as the active and the following inactive ingredients: glacial acetic acid USP 2 mg, sodium chloride 7 mg, sodium acetate (trihydrate) USP 2 mg, and water for injection, q.s.
Glacial acetic acid USP and sodium acetate (trihydrate) USP are added to provide a buffered solution, pH range 3.9 to 4.5. The molecular weight of octreotide acetate, USP is 1019.3 (free peptide, C₄₉ H₆₆ N₁₀ O₁₀ S₂ ) and its amino acid sequence is:

CLINICAL PHARMACOLOGY

Octreotide acetate exerts pharmacologic actions similar to the natural hormone, somatostatin. It is an even more potent inhibitor of growth hormone, glucagon, and insulin than somatostatin. Like somatostatin, it also suppresses LH response to GnRH, decreases splanchnic blood flow, and inhibits release of serotonin, gastrin, vasoactive intestinal peptide, secretin, motilin, and pancreatic polypeptide.
By virtue of these pharmacological actions, octreotide acetate has been used to treat the symptoms associated with metastatic carcinoid tumors (flushing and diarrhea), and Vasoactive Intestinal Peptide (VIP) secreting adenomas (watery diarrhea). Octreotide acetate substantially reduces growth hormone and/or IGF-I (somatomedin C) levels in patients with acromegaly. Single doses of octreotide acetate have been shown to inhibit gallbladder contractility and to decrease bile secretion in normal volunteers. In controlled clinical trials the incidence of gallstone or biliary sludge formation was markedly increased (see WARNINGS).
Octreotide acetate suppresses secretion of thyroid stimulating hormone (TSH).

Pharmacokinetics

After subcutaneous injection, octreotide is absorbed rapidly and completely from the injection site. Peak concentrations of 5.2 ng/mL (100 mcg dose) were reached 0.4 hours after dosing. Using a specific radioimmunoassay, intravenous and subcutaneous doses were found to be bioequivalent. Peak concentrations and area under the curve values were dose proportional after intravenous single doses up to 200 mcg and subcutaneous single doses up to 500 mcg and after subcutaneous multiple doses up to 500 mcg t.i.d. (1,500 mcg/day).
In healthy volunteers the distribution of octreotide from plasma was rapid (t_α ½= 0.2 h), the volume of distribution (Vdss) was estimated to be 13.6 L, and the total body clearance ranged from 7 L/hr to 10 L/hr. In blood, the distribution into the erythrocytes was found to be negligible and about 65% was bound in the plasma in a concentration-independent manner. Binding was mainly to lipoprotein and, to a lesser extent, to albumin.
The elimination of octreotide from plasma had an apparent half-life of 1.7 to 1.9 hours compared with 1 to 3 minutes with the natural hormone. The duration of action of octreotide acetate is variable but extends up to 12 hours depending upon the type of tumor. About 32% of the dose is excreted unchanged into the urine. In an elderly population, dose adjustments may be necessary due to a significant increase in the half-life (46%) and a significant decrease in the clearance (26%) of the drug.
In patients with acromegaly, the pharmacokinetics differ somewhat from those in healthy volunteers. A mean peak concentration of 2.8 ng/mL (100 mcg dose) was reached in 0.7 hours after subcutaneous dosing. The volume of distribution (Vdss) was estimated to be 21.6 ± 8.5 L and the total body clearance was increased to 18 L/h. The mean percent of the drug bound was 41.2%. The disposition and elimination half-lives were similar to normals.In patients with renal impairment the elimination of octreotide from plasma was prolonged and total body clearance reduced. In mild renal impairment (Cl_CR 40 to 60 mL/min) octreotide t_1/2 was 2.4 hours and total body clearance was 8.8 L/hr, in moderate impairment (Cl_{c R} 10 to 39 mL/min) t_1/2 was 3 hours and total body clearance 7.3 L/hr, and in severely renally impaired patients not requiring dialysis (Cl_CR <10 mL/min) t_1/2 was 3.1 hours and total body clearance was 7.6 L/hr. In patients with severe renal failure requiring dialysis, total body clearance was reduced to about half that found in healthy subjects (from approximately 10 L/hr to 4.5 L/hr). Patients with liver cirrhosis showed prolonged elimination of drug, with octreotide t_1/2 increasing to 3.7 hr and total body clearance decreasing to 5.9 L/hr, whereas patients with fatty liver disease showed t_1/2 increased to 3.4 hr and total body clearance of 8.2 L/hr.

INDICATIONS & USAGE

Acromegaly
Octreotide acetate injection is indicated to reduce blood levels of growth hormone and IGF-I (somatomedin C) in acromegaly patients who have had inadequate response to or cannot be treated with surgical resection, pituitary irradiation, and bromocriptine mesylate at maximally tolerated doses. The goal is to achieve normalization of growth hormone and IGF-I (somatomedin C) levels (see DOSAGE AND ADMINISTRATION). In patients with acromegaly, octreotide acetate injection reduces growth hormone to within normal ranges in 50% of patients and reduces IGF-I (somatomedin C) to within normal ranges in 50% to 60% of patients. Since the effects of pituitary irradiation may not become maximal for several years, adjunctive therapy with octreotide acetate injection to reduce blood levels of growth hormone and IGF-I (somatomedin C) offers potential benefit before the effects of irradiation are manifested. Improvement in clinical signs and symptoms or reduction in tumor size or rate of growth were not shown in clinical trials performed with octreotide acetate injection; these trials were not optimally designed to detect such effects.
Carcinoid Tumors
Octreotide acetate injection is indicated for the symptomatic treatment of patients with metastatic carcinoid tumors where it suppresses or inhibits the severe diarrhea and flushing episodes associated with the disease.
Octreotide acetate injection studies were not designed to show an effect on the size, rate of growth or development of metastases.
Vasoactive Intestinal Peptide Tumors (VIPomas) Octreotide acetate injection is indicated for the treatment of the profuse watery diarrhea associated with VIP-secreting tumors. Octreotide acetate injection studies were not designed to show an effect on the size, rate of growth or development of metastases.

CONTRAINDICATIONS

Sensitivity to this drug or any of its components.

WARNINGS

Single doses of octreotide acetate have been shown to inhibit gallbladder contractility and decrease bile secretion in normal volunteers. In clinical trials (primarily patients with acromegaly or psoriasis), the incidence of biliary tract abnormalities was 63% (27% gallstones, 24% sludge without stones, 12% biliary duct dilatation). The incidence of stones or sludge in patients who received octreotide acetate for 12 months or longer was 52%. Less than 2% of patients treated with octreotide acetate for 1 month or less developed gallstones. The incidence of gallstones did not appear related to age, sex or dose. Like patients without gallbladder abnormalities, the majority of patients developing gallbladder abnormalities on ultrasound had gastrointestinal symptoms. The symptoms were not specific for gallbladder disease. A few patients developed acute cholecystitis, ascending cholangitis, biliary obstruction, cholestatic hepatitis, or pancreatitis during octreotide acetate therapy or following its withdrawal. One patient developed ascending cholangitis during octreotide acetate therapy and died.

PRECAUTIONS

General

Octreotide acetate alters the balance between the counter-regulatory hormones, insulin, glucagon and growth hormone, which may result in hypoglycemia or hyperglycemia. Octreotide acetate also suppresses secretion of thyroid stimulating hormone, which may result in hypothyroidism. Cardiac conduction abnormalities have also occurred during treatment with octreotide acetate. However, the incidence of these adverse events during long-term therapy was determined vigorously only in acromegaly patients who, due to their underlying disease and/or the subsequent treatment they receive, are at an increased risk for the development of diabetes mellitus, hypothyroidism, and cardiovascular disease. Although the degree to which these abnormalities are related to octreotide acetate therapy is not clear, new abnormalities of glycemic control, thyroid function and ECG developed during octreotide acetate therapy as described below.