""Nonfunctional" adrenal tumors may be anything but, new research suggests.
In a study published online August 2, 2016 in the Annals of Internal Medicine, Diana Lopez, MD, of Brigham and Women's Hospital and Harvard Medical Sc"...
Lactic acidosis is a rare, but serious, metabolic complication that can occur due to metformin accumulation during treatment with PrandiMet; when it occurs, it is fatal in approximately 50% of cases. Lactic acidosis may also occur in association with a number of pathophysiologic conditions, including diabetes mellitus, and whenever there is significant tissue hypoperfusion and hypoxemia. Lactic acidosis is characterized by elevated blood lactate levels (>5 mmol/L), decreased blood pH, electrolyte disturbances with an increased anion gap, and an increased lactate/pyruvate ratio. When metformin is implicated as the cause of lactic acidosis, metformin plasma levels >5 μg/mL are generally found.
The reported incidence of lactic acidosis in patients receiving metformin HCl is very low (approximately 0.03 cases/1,000 patient-years of exposure, with approximately 0.015 fatal cases/1,000 patient-years of exposure). In more than 20,000 patient-years exposure to metformin HCl in clinical trials, there were no reports of lactic acidosis. Reported cases have occurred primarily in diabetic patients with significant renal impairment, including both intrinsic renal disease and renal hypoperfusion, often in the setting of multiple concomitant medical/surgical problems and multiple concomitant medications. Patients with congestive heart failure requiring pharmacologic management, in particular those with unstable or acute congestive heart failure who are at risk of hypoperfusion and hypoxemia, are at increased risk of lactic acidosis. The risk of lactic acidosis increases with the degree of renal impairment and the patient's age. The risk of lactic acidosis may, therefore, be significantly decreased by regular monitoring of renal function in patients taking PrandiMet and by use of the minimum effective dose of PrandiMet. In particular, treatment of the elderly should be accompanied by careful monitoring of renal function. Treatment with PrandiMet should not be initiated in patients ≥80 years of age unless measurement of creatinine clearance demonstrates that renal function is not reduced, as these patients are more susceptible to developing lactic acidosis. In addition, PrandiMet should be promptly withheld in the presence of any condition associated with hypoxemia, dehydration, or sepsis. Because impaired hepatic function may significantly limit the ability to clear lactate, PrandiMet should generally be avoided in patients with clinical or laboratory evidence of hepatic disease. Patients should be cautioned against excessive alcohol intake, either acute or chronic, when taking PrandiMet, since alcohol potentiates the effects of metformin HCl on lactate metabolism. In addition, PrandiMet should be temporarily discontinued prior to any intravascular radiocontrast study and for any surgical procedure.
The onset of lactic acidosis often is subtle, and accompanied only by nonspecific symptoms such as malaise, myalgias, respiratory distress, increasing somnolence, and nonspecific abdominal distress. There may be associated hypothermia, hypotension, and resistant bradyarrhythmias with more marked acidosis. The patient and the patient's physician must be aware of the possible importance of such symptoms and the patient should be instructed to notify the physician immediately if they occur. PrandiMet should be withdrawn until the situation is clarified. Serum electrolytes, ketones, blood glucose and, if indicated, blood pH, lactate levels, and even blood metformin levels may be useful. Once a patient is stabilized on any dose level of PrandiMet, gastrointestinal symptoms, which are common during initiation of therapy, are unlikely to be drug related. Later occurrence of gastrointestinal symptoms could be due to lactic acidosis or other serious disease.
Levels of fasting venous plasma lactate above the upper limit of normal but less than 5 mmol/L in patients taking PrandiMet do not necessarily indicate impending lactic acidosis and may be explainable by other mechanisms, such as poorly controlled diabetes or obesity, vigorous physical activity or technical problems in sample handling.
Lactic acidosis is a medical emergency that must be treated in a hospital setting. In a patient with lactic acidosis who is taking PrandiMet, the drug should be discontinued immediately and general supportive measures promptly instituted. Because metformin HCl is dialyzable (with a clearance of up to 170 mL/min under good hemodynamic conditions), prompt hemodialysis is recommended to correct the acidosis and remove the accumulated metformin. Such management often results in prompt reversal of symptoms and recovery [see CONTRAINDICATIONS].
Impaired Renal Function
Patients with renal impairment should not receive PrandiMet [see CONTRAINDICATIONS].
As metformin is substantially excreted by the kidney, before initiation of therapy with PrandiMet and at least annually thereafter, renal function should be assessed and verified as normal. In patients in whom development of renal impairment is anticipated, renal function should be assessed more frequently and PrandiMet discontinued if evidence of renal impairment is present [see CLINICAL PHARMACOLOGY ].
Radiologic Studies with Intravascular Iodinated Contrast Materials
Intravascular contrast studies with iodinated materials can lead to acute alteration of renal function and have been associated with lactic acidosis in patients receiving metformin HCl [see CONTRAINDICATIONS]. Therefore, in patients in whom any such study is planned, PrandiMet should be temporarily discontinued at the time of or prior to the procedure, and withheld for 48 hours subsequent to the procedure and reinstituted only after renal function has been re-evaluated and found to be normal.
Impaired Hepatic Function
Hepatic impairment has been associated with some cases of lactic acidosis. Therefore, PrandiMet should generally be avoided in patients with hepatic impairment [see CLINICAL PHARMACOLOGY].
Alcohol potentiates the effect of metformin on lactate metabolism. Patients should be warned against excessive alcohol intake while receiving PrandiMet.
Combination with NPH-insulin
Repaglinide is not indicated for use in combination with NPH-insulin.
Across seven controlled clinical trials, there were six serious adverse events (1.4%) of myocardial ischemia with repaglinide in combination with NPH-insulin compared to one event (0.3%) in patients using insulin alone [see ADVERSE REACTIONS].
Repaglinide is partly metabolized by CYP2C8 and CYP3A4 and appears to be a substrate for active hepatic uptake transporter (organic anion transporting protein OATP1B1). Drugs that inhibit CYP2C8, CYP3A4, or OATP1B1 (e.g., cyclosporine) may increase plasma concentrations of repaglinide. Dose reduction of repaglinide may be needed [see DRUG INTERACTIONS and CLINICAL PHARMACOLOGY ].
Most blood glucose-lowering drugs, including repaglinide, can cause hypoglycemia. Patients who have not previously been treated with a meglitinide should be started on the lowest available repaglinide component of PrandiMet to reduce the risk of hypoglycemia. Elderly, debilitated or malnourished patients and those with adrenal or pituitary insufficiency or alcohol intoxication are particularly susceptible to hypoglycemia. Hypoglycemia may be difficult to recognize in the elderly and in people who are taking β-adrenergic blocking drugs [see ADVERSE REACTIONS].
Vitamin B12 Levels
In controlled clinical trials of metformin HCl of 29 weeks' duration, a decrease to subnormal levels of previously normal serum vitamin B12 levels, without clinical manifestations, was observed in approximately 7% of patients. This finding, possibly due to interference with B12 absorption from the B12-intrinsic factor complex, is rarely associated with anemia and appears to be rapidly reversible with discontinuation of metformin HCl or vitamin B12 supplementation. Measurement of hematologic parameters on an annual basis is advised in patients on PrandiMet and any apparent abnormalities should be appropriately investigated and managed.
Certain individuals (those with inadequate vitamin B12 or calcium intake or absorption) appear to be predisposed to developing subnormal vitamin B12 levels. In these patients, routine serum vitamin B12 measurements at 2- to 3-year intervals may be useful.
Use of PrandiMet should be temporarily suspended for any surgical procedure (except minor procedures not associated with restricted intake of food and fluids) and should not be restarted until the patient's oral intake has resumed and renal function has been evaluated as normal.
Loss of Control of Blood Glucose
When a patient stabilized on any diabetic regimen is exposed to stress such as fever, trauma, infection, or surgery, a temporary loss of glycemic control may occur. At such times, it may be necessary to withhold PrandiMet and temporarily administer insulin. PrandiMet may be reinstituted after the acute episode is resolved.
Use of Concomitant Medications Affecting Renal Function or Metformin Disposition
Concomitant medication(s) that may affect renal function or result in significant hemodynamic change or may interfere with the disposition of metformin, such as cationic drugs that are eliminated by renal tubular secretion [see DRUG INTERACTIONS] should be used with caution.
Hypoxic States Cardiovascular collapse (shock) from whatever cause, acute congestive heart failure, acute myocardial infarction, and other conditions characterized by hypoxemia have been associated with lactic acidosis and may also cause prerenal azotemia. When such events occur in patients receiving PrandiMet, the drug should be promptly discontinued.
Change in Clinical Status of Patients with Previously Controlled Type 2 Diabetes
A patient with type 2 diabetes previously well-controlled on PrandiMet who develops laboratory abnormalities or clinical illness (especially vague and poorly defined illness) should be evaluated promptly for evidence of ketoacidosis or lactic acidosis. Evaluation should include serum electrolytes and ketones, blood glucose and, if indicated, blood pH, lactate, pyruvate, and metformin levels. If acidosis of either form occurs, PrandiMet must be stopped immediately and other appropriate corrective measures initiated.
There have been no clinical studies establishing conclusive evidence of macrovascular risk reduction with PrandiMet or any other oral anti-diabetic drug.
Carcinogenesis, Mutagenesis, Impairment of Fertility
No animal studies have been conducted with the combined products in PrandiMet to evaluate carcinogenesis, mutagenesis and impairment of fertility. The following data are based on findings in studies performed with the individual components.
In a 104-week carcinogenicity study in rats at doses up to 120 mg/kg/day, the incidences of benign adenomas of the thyroid and liver were increased in male rats. The higher incidences of thyroid and liver tumors in male rats were not seen at lower dose of 30 mg/kg/day and 60 mg/kg/day respectively (which are over 15 and 30 times, respectively, clinical exposures on a mg/m² basis).
In a 104-week carcinogenicity study in mice at doses up to 500 mg/kg/day, no evidence of carcinogenicity was found in mice (which is approximately 125 times clinical exposure on a mg/m² basis).
Repaglinide was non-genotoxic in a battery of in vivo and in vitro studies: Bacterial mutagenesis (Ames test), in vitro forward cell mutation assay in V79 cells (HGPRT), in vitro chromosomal aberration assay in human lymphocytes, unscheduled and replicating DNA synthesis in rat liver, and in vivo mouse and rat micronucleus tests.
In a rat fertility study, repaglinide was administered to male and female rats at doses up to 300 and 80 mg/kg/day, respectively. No adverse effects on fertility were observed (which are over 40 times clinical exposure on a mg/m² basis).
In a 104-week carcinogenicity study in rats at doses up to 900 mg/kg/day, the incidences of benign stromal uterine polyps were increased in female rats at 900 mg/kg/day (which is approximately four times the maximal recommended human daily dose of 2000 mg of metformin HCl component of PrandiMet on a mg/m² basis).
In a 91-week carcinogenicity study in mice at doses up to 1500 mg/kg/day, no evidence of carcinogenicity was found in mice (which is approximately four times the maximal recommended human daily dose of 2000 mg of metformin HCl component of PrandiMet on a mg/m² basis).
There was no evidence of a mutagenic potential of metformin HCl alone in the following in vitro tests: Ames test (S. typhimurium), gene mutation test (mouse lymphoma cells), or chromosomal aberrations test (human lymphocytes). Results in the in vivo mouse micronucleus test were also negative.
In a rat fertility study, metformin HCl was administered to male and female rats at doses up to 600 mg/kg/day. No adverse effects on fertility were observed (which is approximately three times the maximal recommended human daily dose of 2000 mg of metformin HCl component of PrandiMet on a mg/m² basis).
Use In Specific Populations
Pregnancy Category C
There are no adequate and well-controlled studies in pregnant women with PrandiMet or its individual components. Because animal reproduction studies are not always predictive of human response, PrandiMet like other antidiabetic medications, should be used during pregnancy only if clearly needed.
No animal studies have been conducted with the combined products in PrandiMet. The following data are based on findings in studies performed with repaglinide or metformin individually.
Repaglinide was not teratogenic in rats at doses 40 times, and rabbits approximately 0.8 times the clinical exposure (on a mg/m² basis) throughout pregnancy. Offspring of rat dams exposed to repaglinide at 15 times clinical exposure on a mg/m² basis during days 17 to 22 of gestation and during lactation developed nonteratogenic skeletal deformities consisting of shortening, thickening, and bending of the humerus during the postnatal period. This effect was not seen at doses up to 2.5 times clinical exposure (on a mg/m² basis) on days 1 to 22 of pregnancy or at higher doses given during days 1 to 16 of pregnancy. Relevant human exposure has not occurred to date and therefore the safety of repaglinide administration throughout pregnancy or lactation cannot be established.
Metformin HCl alone was not teratogenic in rats or rabbits at doses up to 600 mg/kg/day. This represents an exposure of approximately two and six times the near-maximal efficacious human daily dose of 2000 mg of the metformin HCl component of PrandiMet based on body surface area comparisons for rats and rabbits, respectively. Determination of fetal concentrations demonstrated a partial placental barrier to metformin.
No studies in lactating animals have been conducted with the PrandiMet fixed dose combination. In studies performed with individual components, both repaglinide and metformin are excreted into milk of lactating rats.
In rat reproduction studies, measurable levels of repaglinide were detected in the breast milk of the dams and lowered blood glucose levels were observed in the pups. Cross fostering studies indicated that skeletal changes could be induced in control pups nursed by treated dams, although this occurred to a lesser degree than those pups treated in utero.
Studies in lactating rats with metformin HCl show that it is excreted into milk and reaches levels comparable to those in plasma. It is not known whether repaglinide or metformin are excreted in human milk. PrandiMet is not recommended in nursing mothers because it may potentially cause hypoglycemia in nursing infants.
Safety and effectiveness of PrandiMet in pediatric patients have not been established. PrandiMet is not recommended for use in children.
Healthy volunteers treated with repaglinide 2 mg before each of 3 meals, showed no significant differences in repaglinide pharmacokinetics between the group of patients <65 years of age and those ≥65 years of age. In patients with advanced age, PrandiMet should be carefully titrated to establish the minimum dose for adequate glycemic effect, because aging is associated with reduced renal function. In elderly patients, particularly those ≥80 years of age, dose adjustment of PrandiMet should be based on a careful assessment of renal function [see WARNINGS AND PRECAUTIONS, CONTRAINDICATIONS, CLINICAL PHARMACOLOGY].This monograph has been modified to include the generic and brand name in many instances.
Last reviewed on RxList: 11/29/2016
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