Approved Drug Label (PDF)
6
Adverse Reactions
6.1 Clinical Trials Experience
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refer to label)
6.2 Postmarketing Experience
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are underlined)
The following adverse
reactions have been identified during post-approval use of RELISTOR injection.
Because reactions are reported voluntarily from a population of
uncertain size, it is not always possible to reliably estimate the
frequency or establish a causal relationship to drug exposure.
7
Drug Interactions
7.2 Drugs Metabolized by Cytochrome P450 Isozymes
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are underlined)
In
healthy subjects, a subcutaneous dose of 0.3 mg/kg of RELISTOR
did not significantly affect the metabolism of dextromethorphan, a CYP2D6
substrate.
8
Use in Specific Populations
8.1 Pregnancy
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are underlined)
Risk
Summary
The
limited available data with RELISTOR in pregnant women are not sufficient to inform a
drug-associated risk for major birth defects and miscarriages. There are
clinical considerations when RELISTOR is used by pregnant women. In animal reproduction studies, no
effects on embryofetal development were observed with the administration of
intravenous methylnaltrexone bromide during organogenesis in rats and rabbits
at doses up to 20 times and 26 times, respectively, the subcutaneous maximum
recommended human dose (MRHD) of 12 mg RELISTOR injection per day. The
intravenous doses in rats and rabbits are about 0.5 times and 0.7 times,
respectively, the oral MRHD of 450 mg/day. Advise pregnant women of the
potential risk to a fetus.
The
estimated background risk of major birth defects and miscarriage for the indicated
population is unknown. In the U.S. general population, the estimated background
risk of major birth defects and miscarriage in clinically recognized
pregnancies is 2 to 4% and 15 to 20%, respectively.
Clinical
Considerations
Fetal/Neonatal Adverse
Reactions
The
use of RELISTOR during pregnancy may precipitate opioid withdrawal in a fetus
due to the immature fetal blood-brain barrier.
Data
Animal Data
Reproduction
studies have been performed with methylnaltrexone bromide administered
during the period of organogenesis to rats at intravenous doses up to 25
mg/kg/day (about 20 times the subcutaneous MRHD of 12 mg/day
based on body surface area), and did not cause any adverse effects on
embryofetal development. In rabbits, intravenous doses of methylnaltrexone bromide
up to 16 mg/kg/day (about 26 times the subcutaneous MRHD of 12
mg/day) did not show any embryofetal toxicity. The intravenous doses in rats
(25 mg/kg/day) and rabbits (16 mg/kg/day) are about 0.5 and 0.7 times,
respectively, the oral MRHD of 450 mg/day based on body surface area. A
pre- and postnatal development study in rats showed no evidence of any adverse
effect on pre- and postnatal development at subcutaneous doses of
methylnaltrexone bromide up to 100 mg/kg/day (about 81 times the
subcutaneous MRHD of 12 mg/day; about 2.2 times the oral MRHD of 450 mg/day).
8.2 Lactation
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Risk
Summary
There
is no information regarding the presence of methylnaltrexone in human milk, the
effects on the breastfed infant, or the effects on milk production.
Methylnaltrexone is present in rat milk. Because
of the potential for serious adverse reactions, including opioid withdrawal, in
breastfed infants, advise women that breastfeeding is not recommended during
treatment with RELISTOR.
Data
Radioactivity
appeared in rat milk within 30 minutes of a single subcutaneous administration
of radiolabeled methylnaltrexone bromide and was concentrated up to 24-fold at
8 hours after administration relative to plasma concentrations.
8.4 Pediatric Use
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are underlined)
Safety
and effectiveness of RELISTOR tablets and injection have not been
established in pediatric patients.
Juvenile
Animal Studies
In
juvenile rats administered intravenous methylnaltrexone bromide for 13 weeks,
adverse clinical signs such as convulsions, tremors and labored breathing were
observed, and the juvenile rats were found to be more sensitive to the adverse
effects of methylnaltrexone when compared to adult animals.
8.5 Geriatric Use
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are underlined)
Of the total number of
patients in clinical studies of RELISTOR tablets, a total of 136
patients (10%) were aged 65 years and older, while 23 (2%) were
aged 75 and older. In clinical studies of RELISTOR tablets, no overall differences
in effectiveness were observed. Adverse reactions in
were similar; however, there was a higher incidence of diarrhea in elderly
patients.
Of the
total number of patients in clinical studies of RELISTOR injection, a total of
226 (28%) were aged 65 years and older, while 108 (13%) were aged 75 years and
older. In clinical studies of RELISTOR injection, no overall differences in
safety or effectiveness were observed between elderly patients and
younger patients.
Based
on pharmacokinetic data, and safety and efficacy data from controlled clinical
trials, no dosage adjustment based on age is recommended. Monitor
elderly patients for adverse reactions.
8.6 Renal Impairment
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are underlined)
In a study of subjects with
varying degrees of renal impairment receiving
RELISTOR injection subcutaneously, there was a significant increase in the
exposure to methylnaltrexone in subjects with moderate and severe renal
impairment (creatinine clearance less than 60 mL/minute as estimated
by Cockcroft-Gault) compared to healthy subjects.
Therefore, a dosage
reduction of RELISTOR tablets and RELISTOR injection is recommended in patients
with moderate and severe renal impairment. No dosage adjustment of RELISTOR
tablets or RELISTOR injection is needed in patients with mild renal impairment
(creatinine clearance greater than 60 mL/minute as estimated by
Cockcroft-Gault).
8.7 Hepatic Impairment
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are underlined)
Tablets
In a study of subjects
with varying degrees of hepatic impairment receiving a 450 mg dose of RELISTOR
tablets, there was a significant increase in systemic exposure of
methylnaltrexone for subjects with moderate (Child-Pugh Class B) and severe
(Child-Pugh Class C) hepatic impairment compared to healthy subjects with
normal hepatic function. Therefore, a dosage reduction of RELISTOR tablets is
recommended in patients with moderate or severe hepatic impairment. No dosage adjustment of RELISTOR
tablets is needed in patients with mild hepatic impairment (Child-Pugh Class
A).
Injection
In a study of subjects
with mild or moderate hepatic impairment, there was no clinically meaningful
change in systemic exposure of methylnaltrexone compared to healthy subjects
with normal hepatic function. Therefore, no dosage adjustment of RELISTOR
injection is needed for patients with mild or moderate hepatic impairment.
Patients with severe
hepatic impairment were not studied. In patients with severe hepatic
impairment, monitor for methylnaltrexone-related adverse reactions. If
considering dosage adjustment, follow the recommendations in Table 3.