Risk Summary
The data on use of buprenorphine, one of
the active ingredients in buprenorphine and naloxone sublingual tablets,
in pregnancy, are limited; however, these data do not indicate an
increased risk of major malformations specifically due to buprenorphine
exposure. There are limited data from randomized clinical trials in
women maintained on buprenorphine that were not designed appropriately
to assess the risk of major malformations [see Data]. Observational studies
have reported on congenital malformations among buprenorphine-exposed
pregnancies, but were also not designed appropriately to assess the
risk of congenital malformations specifically due to buprenorphine
exposure [see Data]. The extremely limited data on sublingual naloxone exposure in pregnancy
are not sufficient to evaluate a drug-associated risk.
Reproductive and developmental
studies in rats and rabbits identified adverse events at clinically
relevant and higher doses. Embryo-fetal death was also observed in
both rats and rabbits administered buprenorphine during the period
of organogenesis at doses approximately 6 and 0.3 times, respectively,
the human sublingual dose of 16 mg/day of buprenorphine. Pre-and post-natal
development studies in rats demonstrated increased neonatal deaths
at 0.3 times and above and dystocia at approximately 3 times the human
sublingual dose of 16 mg/day of buprenorphine. No clear teratogenic
effects were seen when buprenorphine was administered during organogenesis
with a range of doses equivalent to or greater than the human sublingual
dose of 16 mg/day of buprenorphine. However, increases in skeletal
abnormalities were noted in rats and rabbits administered buprenorphine
daily during organogenesis at doses approximately 0.6 times and approximately
equal to the human sublingual dose of 16 mg/day of buprenorphine,
respectively. In a few studies, some events such as acephalus and
omphalocele were also observed but these findings were not clearly
treatment-related [see Data]. Based on animal data, advise pregnant women of the potential
risk to a fetus.
The
estimated background risk of major birth defects and miscarriage for
the indicated population are unknown. All pregnancies have a background
risk of birth defect, loss, or other adverse outcomes. 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
Disease-associated maternal and embryo-fetal
risk
Untreated
opioid addiction in pregnancy is associated with adverse obstetrical
outcomes such as low birth weight, preterm birth, and fetal death.
In addition, untreated opioid addiction often results in continued
or relapsing illicit opioid use.
Dose Adjustment during Pregnancy and
the Postpartum Period
Dosage adjustments of buprenorphine may be
required during pregnancy, even if the patient was maintained on a
stable dose prior to pregnancy. Withdrawal signs and symptoms should
be monitored closely and the dose adjusted as necessary.
Fetal/neonatal adverse reactions
Neonatal opioid withdrawal
syndrome may occur in newborn infants of mothers who are receiving
treatment with buprenorphine and naloxone sublingual tablets.
Neonatal opioid withdrawal syndrome
presents as irritability, hyperactivity and abnormal sleep pattern,
high pitched cry, tremor, vomiting, diarrhea, and/or failure to gain
weight. Signs of neonatal withdrawal usually occur in the first days
after birth. The duration and severity of neonatal opioid withdrawal
syndrome may vary. Observe newborns for signs of neonatal opioid withdrawal
syndrome and manage accordingly [see Warnings and Precautions
(5.5)].
Labor or Delivery
Opioid-dependent women on buprenorphine
maintenance therapy may require additional analgesia during labor.
Data
Human Data
Studies have been conducted
to evaluate neonatal outcomes in women exposed to buprenorphine during
pregnancy. Limited data from trials, observational studies, case series,
and case reports on buprenorphine use in pregnancy do not indicate
an increased risk of major malformations specifically due to buprenorphine.
Several factors may complicate the interpretation of investigations
of the children of women who take buprenorphine during pregnancy,
including maternal use of illicit drugs, late presentation for prenatal
care, infection, poor compliance, poor nutrition, and psychosocial
circumstances. Interpretation of data is complicated further by the
lack of information on untreated opioid-dependent pregnant women,
who would be the most appropriate group for comparison. Rather, women
on another form of opioid medication-assisted treatment, or women
in the general population are generally used as the comparison group.
However, women in these comparison groups may be different from women
prescribed buprenorphine-containing products with respect to maternal
factors that may lead to poor pregnancy outcomes.
In a multicenter, double-blind, randomized,
controlled trial [Maternal Opioid Treatment: Human Experimental Research
(MOTHER)] designed primarily to assess neonatal opioid withdrawal
effects, opioid-dependent pregnant women were randomized to buprenorphine
(n=86) or methadone (n=89) treatment, with enrollment at an average
gestational age of 18.7 weeks in both groups. A total of 28 of the
86 women in the buprenorphine group (33%) and 16 of the 89 women in
the methadone group (18%) discontinued treatment before the end of
pregnancy.
Among women
who remained in treatment until delivery, there was no difference
between buprenorphine-treated and methadone-treated groups in the
number of neonates requiring NOWS treatment or in the peak severity
of NOWS. Buprenorphine-exposed neonates required less morphine (mean
total dose, 1.1 mg vs. 10.4 mg), had shorter hospital stays (10.0
days vs. 17.5 days), and shorter duration of treatment for NOWS (4.1
days vs. 9.9 days) compared to the methadone-exposed group. There
were no differences between groups in other primary outcomes (neonatal
head circumference) or secondary outcomes (weight and length at birth,
preterm birth, gestational age at delivery, and 1-minute and 5-minute
Apgar scores), or in the rates of maternal or neonatal adverse events.
The outcomes among mothers who discontinued treatment before delivery
and may have relapsed to illicit opioid use are not known. Because
of the imbalance in discontinuation rates between the buprenorphine
and methadone groups, the study findings are difficult to interpret.
Animal Data
The exposure margins
listed below are based on body surface area comparisons (mg/m2) to the human sublingual dose of 16 mg buprenorphine
via buprenorphine and naloxone sublingual tablets.
Effects on embryo-fetal development were
studied in Sprague-Dawley rats and Russian white rabbits following
oral (1:1) and intramuscular (IM) (3:2) administration of mixtures
of buprenorphine and naloxone during the period of organogenesis.
Following oral administration to rats, no teratogenic effects were
observed at buprenorphine doses up to 250 mg/kg/day (estimated exposure
approximately 150 times the human sublingual dose of 16 mg) in the
presence of maternal toxicity (mortality). Following oral administration
to rabbits, no teratogenic effects were observed at buprenorphine
doses up to 40 mg/kg/day (estimated exposure approximately 50 times
the human sublingual dose of 16 mg) in the absence of clear maternal
toxicity. No definitive drug-related teratogenic effects were observed
in rats and rabbits at IM doses up to 30 mg/kg/day (estimated exposure
approximately 20 times and 35 times, respectively, the human sublingual
dose of 16 mg). Maternal toxicity resulting in mortality was noted
in these studies in both rats and rabbits. Acephalus was observed
in one rabbit fetus from the low-dose group and omphalocele was observed
in two rabbit fetuses from the same litter in the mid-dose group;
no findings were observed in fetuses from the high-dose group. Maternal
toxicity was seen in the high-dose group but not at the lower doses
where the findings were observed. Following oral administration of
buprenorphine to rats, dose-related post-implantation losses, evidenced
by increases in the numbers of early resorptions with consequent reductions
in the numbers of fetuses, were observed at doses of 10 mg/kg/day
or greater (estimated exposure approximately 6 times the human sublingual
dose of 16 mg). In the rabbit, increased post-implantation losses
occurred at an oral dose of 40 mg/kg/day. Following IM administration
in the rat and the rabbit, post-implantation losses, as evidenced
by decreases in live fetuses and increases in resorptions, occurred
at 30 mg/kg/day.
Buprenorphine
was not teratogenic in rats or rabbits after IM or subcutaneous (SC)
doses up to 5 mg/kg/day (estimated exposure was approximately 3 and
6 times, respectively, the human sublingual dose of 16 mg), after
IV doses up to 0.8 mg/kg/day (estimated exposure was approximately
0.5 times and equal to, respectively, the human sublingual dose of
16 mg), or after oral doses up to 160 mg/kg/day in rats (estimated
exposure was approximately 95 times the human sublingual dose of 16
mg) and 25 mg/kg/day in rabbits (estimated exposure was approximately
30 times the human sublingual dose of 16 mg). Significant increases
in skeletal abnormalities (e.g., extra thoracic vertebra or thoraco-lumbar
ribs) were noted in rats after SC administration of 1 mg/kg/day and
up (estimated exposure was approximately 0.6 times the human sublingual
dose of 16 mg), but were not observed at oral doses up to 160 mg/kg/day.
Increases in skeletal abnormalities in rabbits after IM administration
of 5 mg/kg/day (estimated exposure was approximately 6 times the human
sublingual dose of 16 mg) in the absence of maternal toxicity or oral
administration of 1 mg/kg/day or greater (estimated exposure was approximately
equal to the human sublingual dose of 16 mg) were not statistically
significant.
In rabbits,
buprenorphine produced statistically significant pre-implantation
losses at oral doses of 1 mg/kg/day or greater and post-implantation
losses that were statistically significant at IV doses of 0.2 mg/kg/day
or greater (estimated exposure approximately 0.3 times the human sublingual
dose of 16 mg). No maternal toxicity was noted at doses causing post-implantation
loss in this study.
Dystocia was noted in pregnant rats treated intramuscularly with
buprenorphine from Gestation Day 14 through Lactation Day 21 at 5
mg/kg/day (approximately 3 times the human sublingual dose of 16 mg).
Fertility, and pre- and postnatal development studies with buprenorphine
in rats indicated increases in neonatal mortality after oral doses
of 0.8 mg/kg/day and up (approximately 0.5 times the human sublingual
dose of 16 mg), after IM doses of 0.5 mg/kg/day and up (approximately
0.3 times the human sublingual dose of 16 mg), and after SC doses
of 0.1 mg/kg/day and up (approximately 0.06 times the human sublingual
dose of 16 mg). An apparent lack of milk production during these studies
likely contributed to the decreased pup viability and lactation indices.
Delays in the occurrence of righting reflex and startle response were
noted in rat pups at an oral dose of 80 mg/kg/day (approximately 50
times the human sublingual dose of 16 mg).