Drug Levels and Effects:

Summary of Use during Lactation:

Because there is little published experience with clozapine during breastfeeding, and sedation and adverse hematologic effects have been reported in breastfed infants, other agents are preferred. If breastfeeding is undertaken by a mother who is taking clozapine, close monitoring of the infant for excessive sedation and periodic monitoring of the infant's white blood cell count is advisable.

Drug Levels:

Maternal Levels.

A woman taking oral clozapine 50 mg daily had a milk clozapine level of 63.5 mcg/L one day postpartum. At 3 days postpartum her dose was increased to 100 mg daily, and at 7 days postpartum clozapine in milk was 115.6 mcg/L. Her infant was not breastfed and timing of the samples with respect to the doses was not stated.[1]

Infant Levels.

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

Effects in Breastfed Infants:

Among 4 infants who were breastfed by mothers taking clozapine, 1 infant experienced drowsiness and 1 infant experienced agranulocytosis possibly caused by clozapine. Details of the cases are lacking.[2]

A healthy female infant was born to a mother who took clozapine 100 mg daily throughout pregnancy and lactation. She was breastfed (extent not stated) up to 1 year of age. The infant developed normally except for speech which was delayed considerably. She did not achieve normal, fluent speech until the age of 5 years. The delayed speech development was possibly related to clozapine in breastmilk, but it could have been the result of exposure to the drug during gestation or unrelated to clozapine.[3]

Possible Effects on Lactation:

Unlike the phenothiazines, clozapine has a minimal effect on maternal serum prolactin levels.[4][5] However, a woman who had been taking clozapine plus high-dosehaloperidoldeveloped hyperprolactinemia and severe galactorrhea 2 weeks after stoppinghaloperidoland 4 days after starting valproic acid. A dose of cabergoline normalized her serum prolactin and galactorrhea ceased for the following 2 months of observation.[6]

The maternal prolactin level in a mother with established lactation may not affect her ability to breastfeed.

Alternate Drugs to Consider:



1. Barnas C, Bergant A, Hummer M et al. Clozapine concentrations in maternal and fetal plasma, amniotic fluid, and breast milk. Am J Psychiatry. 1994;151:945. Letter. PMID:8185013
2. Dev VJ, Krupp P. Adverse event profile and safety of clozapine. Rev Contemp Pharmacother. 1995;6:197-208.
3. Mendhekar DN. Possible delayed speech acquisition with clozapine therapy during pregnancy and lactation. J Neuropsychiatry Clin Neurosci. 2007;19:196-7. PMID:17431071
4. Maguire GA. Prolactin elevation with antipsychotic medications: mechanisms of action and clinical consequences. J Clin Psychiatry. 2002;63 (Suppl 4):56-62. PMID:11913677
5. Bergemann N, Mundt C, Parzer P et al. Plasma concentrations of estradiol in women suffering from schizophrenia treated with conventional versus atypical antipsychotics. Schizophr Res. 2005;73:357-66. PMID:15653282
6. Conca A, Waler M, Walpoth M et al. A case of delayed galactorrhoea as an adverse event of overlappinghaloperidoland clozapine administration. Int J Neuropsychopharmacol. 2005;8:303-5. PMID:15850503

Substance Identification:

Substance Name:


CAS Registry Number:


Drug Class:

  • Antipsychotic Agents

  • Administrative Information:

    LactMed Record Number:


    Last Revision Date:

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