Patients who receive octreotide acetate injection intravenously may be at increased risk for higher degree atrioventricular blocks. In postmarketing reports, complete atrioventricular block was reported in patients receiving intravenous octreotide acetate injection during surgical procedures. In majority of patients, octreotide acetate injection was given at higher than recommended doses and/or as a continuous intravenous infusion. The safety of continuous intravenous infusion has not been established in patients receiving octreotide acetate injection for the approved indications. Consider cardiac monitoring in patients receiving octreotide acetate injection intravenously.
Octreotide acetate injection alters the balance between the counter-regulatory hormones, insulin, glucagon and growth hormone (GH), which may result in hypoglycemia or hyperglycemia. Octreotide acetate injection also suppresses secretion of thyroid stimulating hormone, which may result in hypothyroidism. Cardiac conduction abnormalities have also occurred during treatment with octreotide acetate injection. 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 injection therapy is not clear, new abnormalities of glycemic control, thyroid function, and electrocardiogram (ECG) developed during octreotide acetate injection therapy, as described below.
Risk of Pregnancy with Normalization of Insulin Growth Factor-1 (IGF-1; Somatomedin C) and Growth Hormone (GH)
Although acromegaly may lead to infertility, there are reports of pregnancy in acromegalic women. In women with active acromegaly who have been unable to become pregnant, normalization of GH and IGF-1 (somatomedin C) may restore fertility. Female patients of childbearing potential should be advised to use adequate contraception during treatment with octreotide.
The hypoglycemia or hyperglycemia which occurs during octreotide acetate injection therapy is usually mild, but may result in overt diabetes mellitus or necessitate dose changes in insulin or other hypoglycemic agents. Hypoglycemia and hyperglycemia occurred on octreotide acetate injection in 3% and 16% of acromegalic patients, respectively. Severe hyperglycemia, subsequent pneumonia, and death following initiation of octreotide acetate injection therapy was reported in one patient with no history of hyperglycemia.
In patients with concomitant Type I diabetes mellitus, octreotide acetate injection may affect glucose regulation, and insulin requirements may be reduced. Symptomatic hypoglycemia, which may be severe, has been reported in these patients. In nondiabetics and Type II diabetics with partially intact insulin reserves, octreotide acetate injection administration may result in decreases in plasma insulin levels and hyperglycemia. It is therefore recommended that glucose tolerance and antidiabetic treatment be periodically monitored during therapy with these drugs.
In acromegalic patients, 12% developed biochemical hypothyroidism only, 8% developed goiter, and 4% required initiation of thyroid replacement therapy while receiving octreotide acetate injection. Baseline and periodic assessment of thyroid function (TSH, total, and/or free T4 ) is recommended during chronic therapy.
In acromegalics, bradycardia (<50 bpm) developed in 25%; conduction abnormalities occurred in 10% and arrhythmias occurred in 9% of patients during octreotide acetate injection therapy.
Other electrocardiogram (ECG) changes observed included QT prolongation, axis shifts, early repolarization, low voltage, R/S transition, and early R-wave progression. These ECG changes are not uncommon in acromegalic patients.
Dose adjustments in drugs such as beta-blockers that have bradycardia effects may be necessary.
In one acromegalic patient with severe congestive heart failure, initiation of octreotide acetate injection therapy resulted in worsening of congestive heart failure with improvement when drug was discontinued. Confirmation of a drug effect was obtained with a positive rechallenge.
Several cases of pancreatitis have been reported in patients receiving octreotide acetate injection therapy.
Octreotide acetate injection may alter absorption of dietary fats in some patients.
Depressed vitamin B12 levels and abnormal Schilling’s tests have been observed in some patients receiving octreotide acetate injection therapy, and monitoring of vitamin B12 levels is recommended during chronic octreotide acetate injection therapy.
In patients with severe renal failure requiring dialysis, the half-life of octreotide acetate injection may be increased, necessitating adjustment of the maintenance dosage.
Careful instruction in sterile subcutaneous injection technique should be given to the patients and to other persons who may administer octreotide acetate injection. Inform patients that cholelithiasis has been reported with the use of octreotide acetate injection. Advise patients to contact their healthcare provider if they experience signs or symptoms of gallstones (cholelithiasis) or complications of gallstones (e.g., cholecystitis, cholangitis, and pancreatitis).
Laboratory tests that may be helpful as biochemical markers in determining and following patient response depend on the specific tumor. Based on diagnosis, measurement of the following substances may be useful in monitoring the progress of therapy:
Growth hormone (GH), insulin growth factor-1 (IGF-1; somatomedin C) Responsiveness to octreotide acetate injection may be evaluated by determining GH levels at 1 to 4 hour intervals for 8 to 12 hours post dose. Alternatively, a single measurement of IGF-1 (somatomedin C) level may be made two weeks after drug initiation or dosage change.
Carcinoid: urinary 5-hydroxyindole acetic acid (5-HIAA), plasma serotonin, plasma Substance P
VIPoma: plasma vasoactive intestinal peptide (VIP)
Baseline and periodic total and/or free T4 measurements should be performed during chronic therapy (see PRECAUTIONS, General).
Octreotide has been associated with alterations in nutrient absorption, so it may have an effect on absorption of orally administered drugs. Concomitant administration of octreotide acetate injection with cyclosporine may decrease blood levels of cyclosporine and result in transplant rejection.
Patients receiving insulin, oral hypoglycemic agents, beta blockers, calcium channel blockers, or agents to control fluid and electrolyte balance, may require dose adjustments of these therapeutic agents.
Concomitant administration of octreotide and bromocriptine increases the availability of bromocriptine. Limited published data indicate that somatostatin analogs might decrease the metabolic clearance of compounds known to be metabolized by cytochrome P450 enzymes, which may be due to the suppression of growth hormone (GH). Since it cannot be excluded that octreotide may have this effect, other drugs mainly metabolized by CYP3A4 and which have a low therapeutic index (e.g., quinidine, terfenadine) should therefore be used with caution.
No known interference exists with clinical laboratory tests, including amine or peptide determinations.
Studies in laboratory animals have demonstrated no mutagenic potential of octreotide acetate injection.
No carcinogenic potential was demonstrated in mice treated subcutaneously for 85 to 99 weeks at doses up to 2,000 mcg/kg/day (8 x the human exposure based on body surface area). In a 116-week subcutaneous study in rats, a 27% and 12% incidence of injection site sarcomas or squamous cell carcinomas was observed in males and females, respectively, at the highest dose level of 1,250 mcg/kg/day (10 x the human exposure based on body surface area) compared to an incidence of 8% to 10% in the vehicle-control groups. The increased incidence of injection-site tumors was most probably caused by irritation and the high sensitivity of the rat to repeated subcutaneous injections at the same site. Rotating injection sites would prevent chronic irritation in humans. There have been no reports of injection-site tumors in patients treated with octreotide acetate injection for up to 5 years. There was also a 15% incidence of uterine adenocarcinomas in the 1,250 mcg/kg/day females compared to 7% in the saline-control females and 0% in the vehicle-control females. The presence of endometritis coupled with the absence of corpora lutea, the reduction in mammary fibroadenomas, and the presence of uterine dilatation suggest that the uterine tumors were associated with estrogen dominance in the aged female rats which does not occur in humans.
Octreotide acetate injection did not impair fertility in rats at doses up to 1,000 mcg/kg/day, which represents 7x the human exposure based on body surface area.
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