Drug Levels and Effects:

Summary of Use during Lactation:

Maternal clonazepam occasionally causes sedation in their breastfed infants, especially when given with other central nervous system depressants. Monitor the infant for drowsiness, adequate weight gain, and developmental milestones, especially in younger, exclusively breastfed infants and when using combinations of psychotropic drugs. Monitoring of the infant's serum concentration may be indicated if excessive sedation occurs. Safer alternatives to clonazepam are available for use as a general sedative or anxiolytic.

Drug Levels:

In published reports of anticonvulsant use during breastfeeding, most women were taking a combination of anticonvulsants. Some other anticonvulsants (e.g., phenytoin, carbamazepine) stimulate the metabolism of other drugs including anticonvulsants, whereas others (e.g., valproic acid) inhibit the metabolism of other drugs. Therefore, the relationship of the maternal dosage to the concentration in breastmilk can be quite variable, making calculation of the weight-adjusted percentage of maternal dosage less meaningful than for other drugs in this database.

Maternal Levels.

A breastfed newborn infant whose mother was taking clonazepam during pregnancy and lactation (dosage not stated) had serum levels that increased from about 23 mcg/L at 24 hours of age to 43 mcg/L at 96 hours of age.[1]

Repeated milk clonazepam levels were between 11 and 13 mcg/L in a woman taking clonazepam in an unstated dosage.[2]

A mother taking clonazepam 2 mg twice daily had several milk level measurements on days 2 to 4 postpartum. The highest milk level was 10.7 mcg/L 4 hours after a dose. The authors calculated that an exclusively breastfed infant would receive a maximum of 2.5% of the maternal weight-adjusted dosage of clonazepam.[3]

Infant Levels.

One preterm infant had cord blood levels of 19 mcg/L and was not breastfed until 72 hours after delivery. The infant's serum clonazepam level was 2.9 mcg/L at 120 hours after birth, and 1 mcg/L at day 14. The mother's serum level was 32 mcg/L at delivery and repeated milk clonazepam levels were between 11 and 13 mcg/L.[2]

A newborn infant was breastfeeding during a maternal dosage of clonazepam 2 mg twice daily. A pooled sample of infant serum from days 2 to 4 of age contained 4.7 mcg/L of clonazepam.[3]

Ten of 11 breastfed infants whose mothers were taking clonazepam in dosages of 0.25 to 2 mg daily had no detectable (assay limit varied from 5 to 14 mcg/L) clonazepam or metabolites in serum. The infants' average age was 7.9 weeks, but 6 were under 1 month of age. One 1.9 week-old-infant whose mother was taking clonazepam 0.5 mg daily had a serum concentration of 22 mcg/L.[4]

Effects in Breastfed Infants:

Excessive periodic breathing and prolonged apnea and cyanosis occurred in a newborn at 6 hours after birth at 36 weeks gestation and reoccurred repeatedly up to 10 days of age. The neonate was breastfed starting at 72 hours after delivery and her mother took clonazepam (dose not stated) during pregnancy and lactation. The repeated periodic breathing episodes continued up to 10 weeks of age and were possibly related to clonazepam in breastmilk. A neurodevelopmental examination was normal at 5 months of age.[2]

The infant of a mother taking clonazepam 1 mg daily during pregnancy and lactation was rated as highly apathetic and had decreased weight increase and slight neurologic signs at 4 weeks of age, but normal intelligence at 6 years of age.[5]

None of 11 infants whose mothers were taking clonazepam in dosages ranging from 0.25 to 2 mg daily (including 4 who were taking other psychotropic drugs also) had any side effects reported by their mothers. The infants' average age was 7.9 weeks, but 6 were under 1 month of age.[4]

In a telephone follow-up study, 124 mothers who took a benzodiazepine while nursing reported whether their infants had any signs of sedation. Twenty-two mothers took clonazepam while breastfeeding and 1 reported sedation in her infant. She was taking clonazepam 0.25 mg twice daily, flurazepam 15 mg daily, 1 mg ofbupropiondaily, and 0.75 mg of risperidone daily.[6]

Possible Effects on Lactation:

Relevant published information was not found as of the revision date.

Alternate Drugs to Consider:

(Sedative) Lorazepam,Oxazepam


1. Bossi L, Battino D, Caccamo ML et al. Pharmacokinetics and clinical effects of antiepileptic drugs in newborns of chronically treated epileptic mothers. In: Janz D et al, eds. Epilepsy, pregnancy and the child. New York: Raven Press, 1982:373-81.
2. Fisher JB, Edgren BE, Mammel MC et al. Neonatal apnea associated with maternal clonazepam therapy: a case report. Obstet Gynecol. 1985;66 (3 Suppl):34S-5S. PMID:4022513
3. Soderman P, Matheson I. Clonazepam in breast milk. Eur J Pediatr. 1988;147:212-3. Letter. PMID:3366144
4. Birnbaum CS, Cohen LS, Bailey JW et al. Serum concentrations of antidepressants and benzodiazepines in nursing infants: a case series. Pediatrics. 1999;104:e11. PMID:10390297
5. Hartmann AM, Koch S, Jager-Roman E et al. [Breast feeding, weight gain and behaviour in newborns of epileptic women]. Monatsschr Kinderheilkd. 1994;142:505-12.
6. Kelly LE, Poon S, Madadi P, Koren G. Neonatal benzodiazepines exposure during breastfeeding. J Pediatr. 2012;161:448-51. PMID:22504099

Substance Identification:

Substance Name:


CAS Registry Number:


Drug Class:

  • Anticonvulsants

  • Benzodiazepines

  • Administrative Information:

    LactMed Record Number:


    Last Revision Date:

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