PRECAUTIONS
General
Macrovascular Outcomes
There have been no clinical studies establishing
conclusive evidence of macrovascular risk reduction with GLUCOVANCE or any
other antidiabetic drug.
GLUCOVANCE
Hypoglycemia
GLUCOVANCE is capable of producing hypoglycemia or
hypoglycemic symptoms, therefore, proper patient selection, dosing, and
instructions are important to avoid potential hypoglycemic episodes. The risk
of hypoglycemia is increased when caloric intake is deficient, when strenuous
exercise is not compensated by caloric supplementation, or during concomitant
use with other glucose-lowering agents or ethanol. Renal or hepatic
insufficiency may cause elevated drug levels of both glyburide and metformin
hydrochloride, and the hepatic insufficiency may also diminish gluconeogenic
capacity, both of which increase the risk of hypoglycemic reactions. Elderly,
debilitated, or malnourished patients and those with adrenal or pituitary
insufficiency or alcohol intoxication are particularly susceptible to hypoglycemic
effects. Hypoglycemia may be difficult to recognize in the elderly and people
who are taking beta-adrenergic blocking drugs.
Glyburide
Hemolytic Anemia
Treatment of patients with glucose-6-phosphate
dehydrogenase (G6PD) deficiency with sulfonylurea agents can lead to hemolytic
anemia. Because GLUCOVANCE belongs to the class of sulfonylurea agents, caution
should be used in patients with G6PD deficiency and a non-sulfonylurea alternative
should be considered. In postmarketing reports, hemolytic anemia has also been
reported in patients who did not have known G6PD deficiency.
Metformin Hydrochloride
Monitoring of Renal Function
Metformin is known to be substantially excreted by the
kidney, and the risk of metformin accumulation and lactic acidosis increases
with the degree of impairment of renal function. Thus, patients with serum creatinine
levels above the upper limit of normal for their age should not receive
GLUCOVANCE. In patients with advanced age, GLUCOVANCE 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, renal function should be monitored
regularly and, generally, GLUCOVANCE should not be titrated to the maximum dose
(see WARNINGS and DOSAGE AND ADMINISTRATION). Before initiation
of GLUCOVANCE therapy and at least annually thereafter, renal function should
be assessed and verified as normal. In patients in whom development of renal
dysfunction is anticipated, renal function should be assessed more frequently
and GLUCOVANCE discontinued if evidence of renal impairment is present.
Use Of Concomitant Medications That May Affect 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.
Radiologic studies involving the use of intravascular
iodinated contrast materials (for example, intravenous urogram, intravenous
cholangiography, angiography, and computed tomography (CT) scans with intravascular
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 (see CONTRAINDICATIONS).
Therefore, in patients in whom any such study is planned, GLUCOVANCE 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 reevaluated and found to be normal.
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 on
GLUCOVANCE therapy, the drug should be promptly discontinued.
Surgical Procedures
GLUCOVANCE therapy 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.
Alcohol Intake
Alcohol is known to potentiate the effect of metformin on
lactate metabolism. Patients, therefore, should be warned against excessive
alcohol intake, acute or chronic, while receiving GLUCOVANCE. Due to its effect
on the gluconeogenic capacity of the liver, alcohol may also increase the risk
of hypoglycemia.
Impaired Hepatic Function
Since impaired hepatic function has been associated with
some cases of lactic acidosis, GLUCOVANCE should generally be avoided in
patients with clinical or laboratory evidence of hepatic disease.
Vitamin B12 Levels
In controlled clinical trials with metformin of 29 weeks
duration, a decrease to subnormal levels of previously normal serum vitamin B12,
without clinical manifestations, was observed in approximately 7% of patients.
Such decrease, possibly due to interference with B12 absorption from the B12-intrinsic
factor complex is, however, very rarely associated with anemia and appears to
be rapidly reversible with discontinuation of metformin or vitamin B
supplementation. Measurement of hematologic parameters on an annual basis is
advised in patients on metformin and any apparent abnormalities should be
appropriately investigated and managed (see PRECAUTIONS: Laboratory
Tests ).
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.
Change In Clinical Status Of Patients With Previously Controlled Type 2 Diabetes
A patient with type 2 diabetes previously well controlled
on metformin 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, GLUCOVANCE
must be stopped immediately and other appropriate corrective measures initiated
(see also WARNINGS).
Addition of Thiazolidinediones to GLUCOVANCE Therapy
Hypoglycemia
Patients receiving GLUCOVANCE in combination with a
thiazolidinedione may be at risk for hypoglycemia.
Weight Gain
Weight gain was seen with the addition of rosiglitazone
to GLUCOVANCE, similar to that reported for thiazolidinedione therapy alone.
Hepatic Effects
When a thiazolidinedione is used in combination with
GLUCOVANCE, periodic monitoring of liver function tests should be performed in
compliance with the labeled recommendations for the thiazolidinedione.
Information For Patients
GLUCOVANCE
Patients should be informed of the potential risks and
benefits of GLUCOVANCE and alternative modes of therapy. They should also be
informed about the importance of adherence to dietary instructions; a regular
exercise program; and regular testing of blood glucose, glycosylated
hemoglobin, renal function, and hematologic parameters.
The risks of lactic acidosis associated with metformin
therapy, its symptoms, and conditions that predispose to its development, as
noted in the WARNINGS and PRECAUTIONS sections, should be explained to
patients. Patients should be advised to discontinue GLUCOVANCE immediately and promptly
notify their health practitioner if unexplained hyperventilation, myalgia,
malaise, unusual somnolence, or other nonspecific symptoms occur. Once a
patient is stabilized on any dose level of GLUCOVANCE, gastrointestinal
symptoms, which are common during initiation of metformin therapy, are unlikely
to be drug related. Later occurrence of gastrointestinal symptoms could be due
to lactic acidosis or other serious disease.
The risks of hypoglycemia, its symptoms and treatment,
and conditions that predispose to its development should be explained to
patients and responsible family members.
Patients should be counseled against excessive alcohol
intake, either acute or chronic, while receiving GLUCOVANCE. (See PATIENT INFORMATION printed below.)
Laboratory Tests
Periodic fasting blood glucose (FBG) and HbA1c
measurements should be performed to monitor therapeutic response.
Initial and periodic monitoring of hematologic parameters
(eg, hemoglobin/hematocrit and red blood cell indices) and renal function
(serum creatinine) should be performed, at least on an annual basis. While
megaloblastic anemia has rarely been seen with metformin therapy, if this is
suspected, vitamin B12 deficiency should be excluded.
Carcinogenesis, Mutagenesis, Impairment Of Fertility
No animal studies have been conducted with the combined
products in GLUCOVANCE. The following data are based on findings in studies
performed with the individual products.
Glyburide
Studies in rats with glyburide alone at doses up to 300
mg/kg/day (approximately 145 times the maximum recommended human daily [MRHD]
dose of 20 mg for the glyburide component of GLUCOVANCE based on body surface
area comparisons) for 18 months revealed no carcinogenic effects. In a 2-year oncogenicity
study of glyburide in mice, there was no evidence of treatment-related tumors.
There was no evidence of mutagenic potential of glyburide
alone in the following in vitro tests: Salmonella microsome test (Ames
test) and in the DNA damage/alkaline elution assay.
Metformin Hydrochloride
Long-term carcinogenicity studies were performed with
metformin alone in rats (dosing duration of 104 weeks) and mice (dosing
duration of 91 weeks) at doses up to and including 900 mg/kg/day and 1500 mg/kg/day,
respectively. These doses are both approximately 4 times the MRHD dose of 2000
mg of the metformin component of GLUCOVANCE based on body surface area
comparisons. No evidence of carcinogenicity with metformin alone was found in
either male or female mice. Similarly, there was no tumorigenic potential
observed with metformin alone in male rats. There was, however, an increased incidence
of benign stromal uterine polyps in female rats treated with 900 mg/kg/day of
metformin alone.
There was no evidence of a mutagenic potential of
metformin 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.
Fertility of male or female rats was unaffected by
metformin alone when administered at doses as high as 600 mg/kg/day, which is
approximately 3 times the MRHD dose of the metformin component of GLUCOVANCE
based on body surface area comparisons.
Pregnancy
Teratogenic Effects
Pregnancy Category B
Recent information strongly suggests that abnormal blood
glucose levels during pregnancy are associated with a higher incidence of
congenital abnormalities. Most experts recommend that insulin be used during
pregnancy to maintain blood glucose as close to normal as possible. Because animal
reproduction studies are not always predictive of human response, GLUCOVANCE
should not be used during pregnancy unless clearly needed. (See below.)
There are no adequate and well-controlled studies in
pregnant women with GLUCOVANCE or its individual components. No animal studies
have been conducted with the combined products in GLUCOVANCE. The following
data are based on findings in studies performed with the individual products.
Glyburide
Reproduction studies were performed in rats and rabbits
at doses up to 500 times the MRHD dose of 20 mg of the glyburide component of
GLUCOVANCE based on body surface area comparisons and revealed no evidence of
impaired fertility or harm to the fetus due to glyburide.
Metformin Hydrochloride
Metformin alone was not teratogenic in rats or rabbits at
doses up to 600 mg/kg/day. This represents an exposure of about 2 and 6 times
the MRHD dose of 2000 mg of the metformin component of GLUCOVANCE based on body
surface area comparisons for rats and rabbits, respectively. Determination of
fetal concentrations demonstrated a partial placental barrier to metformin.
Nonteratogenic Effects
Prolonged severe hypoglycemia (4-10 days) has been
reported in neonates born to mothers who were receiving a sulfonylurea drug at
the time of delivery. This has been reported more frequently with the use of
agents with prolonged half-lives. It is not recommended that GLUCOVANCE be used
during pregnancy. However, if it is used, GLUCOVANCE should be discontinued at
least 2 weeks before the expected delivery date. (See Pregnancy: Teratogenic
Effects : Pregnancy Category B.)
Nursing Mothers
Although it is not known whether glyburide is excreted in
human milk, some sulfonylurea drugs are known to be excreted in human milk.
Studies in lactating rats show that metformin is excreted into milk and reaches
levels comparable to those in plasma. Similar studies have not been conducted
in nursing mothers. Because the potential for hypoglycemia in nursing infants
may exist, a decision should be made whether to discontinue nursing or to
discontinue GLUCOVANCE, taking into account the importance of the drug to the
mother. If GLUCOVANCE is discontinued, and if diet alone is inadequate for controlling
blood glucose, insulin therapy should be considered.
Pediatric Use
The safety and efficacy of GLUCOVANCE were evaluated in
an active-controlled, double-blind, 26- week randomized trial involving a total
of 167 pediatric patients (ranging from 9-16 years of age) with type 2
diabetes. GLUCOVANCE was not shown statistically to be superior to either
metformin or glyburide with respect to reducing HbA1c from baseline (see Table
5). No unexpected safety findings were associated with GLUCOVANCE in this
trial.
Table 5: HbA1c (Percent) Change From Baseline at 26
Weeks : Pediatric Study
|
Glyburide 2.5 mg tablets |
Metformin 500 mg tablets |
GLUCOVANCE 1.25 mg/250 mg tablets |
Mean Final Dose |
6.5 mg |
1500 mg |
3.1 mg/623 mg |
Hemoglobin Aic |
N=49 |
N=54 |
N=57 |
Baseline Mean (%) |
7.70 |
7.99 |
7.85 |
Mean Change from Baseline |
-0.96 |
-0.48 |
-0.80 |
Difference from Metformin Difference from Glyburide |
|
|
-0.32 +0.16 |
Geriatric Use
Of the 642 patients who received GLUCOVANCE in
double-blind clinical studies, 23.8% were 65 and older while 2.8% were 75 and
older. Of the 1302 patients who received GLUCOVANCE in open-label clinical
studies, 20.7% were 65 and older while 2.5% were 75 and older. No overall
differences in effectiveness or safety were observed between these patients and
younger patients, and other reported clinical experience has not identified
differences in response between the elderly and younger patients, but greater
sensitivity of some older individuals cannot be ruled out.
Metformin hydrochloride is known to be substantially
excreted by the kidney and because the risk of serious adverse reactions to the
drug is greater in patients with impaired renal function, GLUCOVANCE should
only be used in patients with normal renal function (see CONTRAINDICATIONS,
WARNINGS, and CLINICAL PHARMACOLOGY: Pharmacokinetics ).
Because aging is associated with reduced renal function, GLUCOVANCE should be
used with caution as age increases. Care should be taken in dose selection and
should be based on careful and regular monitoring of renal function. Generally,
elderly patients should not be titrated to the maximum dose of GLUCOVANCE (see
also WARNINGS and DOSAGE AND ADMINISTRATION).