Breastfeeding and Drugs

Though many drugs are quite safe for a mother to take while nursing her child there are several agents for which safety during breast-feeding is not well-defined and may be a risk to the infant. Drugs that are contraindicated or should be used with caution by lactating women are described here. You can read more about this in our Motherisk Update on drugs use while breastfeeding.

Drugs Usually Contraindicated While Breastfeeding

Antineoplastics and Immune Suppressants
Even if small amounts of the drug were to be excreted into milk, the inherently toxic nature of these medications warrants caution with their use.

Ergot Alkaloids
Due to the dopaminergic activity of the ergot alkaloids they may have the ability to suppress prolactin and hence lactation. If breast-feeding is to be considered, milk volume must be monitored in mothers. Bromocriptine is used therapeutically to prevent lactation and is therefore contraindicated in nursing mothers. Short term, low dose therapy with ergonovine and methylergonovine does not cause a risk to the infant. However, methylergonovine would be the preferred choice of the two because is does not have prolactin lowering tendencies. Ergotamine is also able to affect milk secretion and is not a preferred choice while nursing because of the risk of ergotism in the infant. Signs of toxicity in the infant include vomiting, weight loss and weak pulse.

Gold
Infants should be closely monitored if breast-fed during maternal gold therapy as the exact effect on infants is not known at this time. Reported milk levels vary widely and aurothiomalite has been measured in both urine and plasma of infants.

Iodine
Iodine containing compounds are not generally recommended during breast-feeding. Iodine readily gains access to breast milk and can lead to hypothyroidism in the infant.

Lithium Carbonate
Breast-feeding during maternal lithium therapy is generally thought to be contraindicated because lithium has been found to attain concentrations in the milk of up to 40% of the maternal weight adjusted dose. Moreover, the excretion of lithium in milk appears to vary a great deal among patients. Since some women will have relatively low excretion of lithium into their milk, and breast-feeding can be extremely beneficial to a manic depressive mother it seems quite reasonable to initiate breast-feeding. It is recommended that infants' serum lithium concentrations be monitored and the infant be observed for signs of toxicity. Breast-feeding may be continued as long as infants' blood levels remain well below therapeutic concentrations and the infant shows no signs of toxicity.

Radiopharmaceuticals
Radioactive materials are contraindicated while breast-feeding, in order to avoid excess infant exposure to radioactivity. Once radioactivity is cleared from the mother's body, however, breast-feeding can be resumed. The length of time of breast-feeding interruption will vary with each radioisotope used depending on radioactive decay and elimination by the mother. Motherisk can be consulted regarding this length of time.

Social Drugs and Drugs of Abuse
Alcohol freely distributes into milk and will be ingested by nursing infants. Moderate, occasional alcohol consumption in not likely to pose a problem to the infant, but heavy alcohol consumption is to be avoided. Ideally nursing should be withheld temporarily after alcohol consumption; at least two hours per drink to avoid unnecessary infant exposure. Side effects reported in infants include sedation and impairment of motor skills.

Cigarette smoking is not recommended in nursing mothers. Nicotine and its major metabolite are detectable in milk. Smoking should be avoided while breast-feeding because it has been associated with infantile colic, lowered maternal prolactin levels and consequently, earlier weaning.

Street drugs can be very potent such that even very small amounts can have pharmacological activity and adverse effects on the infant. It is suggested that breast-feeding be at least temporarily delayed after maternal use of these agents and caution should be used to avoid infant exposure to smoke fumes. Infants may experience toxicity after maternal cocaine use,and marijuana use has been associated with slower motor development at one year of age.

Myla Moretti, Motherisk

Motherisk Research

• Do silicone breast implants affect breastfeeding?
  Gideon Koren, MD, FRCPC; Shinya Ito, MD
• Paediatr Drugs. 2000 Mar-Apr;2(2):113-26. Review.
  Bar-Oz B, Nulman I, Koren G, Ito S: Anticonvulsants and breast feeding: a critical review.
• N Engl J Med. 2000 Jul 13;343(2):118-26.
  Ito S: Drug therapy for breast-feeding women.
• Pediatrics. 2000 Jul;106(1 Pt 1):27-30.
  Lee A, Moretti ME, Collantes A, Chong D, Mazzotta P, Koren G, Merchant SS, Ito S: Choice of breastfeeding and physicians' advice: a cohort study of women receiving propylthiouracil
• J Hum Lact. 1998 Sep;14(3):243-4
  MacDonell JW, Ito S: Breastfeeding anaphylaxis case study.
• Am J Psychiatry. 1997 Aug;154(8):1174. No abstract available.
  Ito S, Koren G: Antidepressants and breast-feeding
• Pediatr Clin North Am. 1997 Feb;44(1):41-54. Review.
  Bailey B, Ito S: Breast-feeding and maternal drug use.
• American Journal of Psychiatry. 154(8):1174, 1997 Aug. No Abstract on-line.
  Ito S. Koren G. Antidepressants and breast-feeding [letter; comment].
• Canadian Medical Association Journal 1997 Jul 1;157(1):16. No Abstract on-line.
  Bailey B, Einarson A, Koren G Alert over sound-alike drugs
• Journal of Clinical Pharmacology 36/11 (1078-1079) 1996. No Abstract on-line.
  Duffull-SB; Begg-EJ; Ilett-KF; Ito-S; Taddio-A; Koren-G Fluoxetine distribution in human milk (multiple letters)
• Pediatric Clinics of North America. 44(1):41-54, 1997 Feb.
  Bailey B. Ito S. Breast-feeding and maternal drug use. [Review] [48 refs]
• Amer J Obstet Gynecol 168: 1393-1399, 1993.
  Ito S, Blachjman A, Stephenson M, Eliopoulos C, Horlatch N, Koren G: Prospective follow-up of adverse reactions in breast-fed infants exposed to maternal medication.
• 
  Koren G, Concentrations of beta blocking drugs in human milk. J Pediatr 16: 156-, 1990.
• 
  Koren G: Toxic effects of atenolol consumed during breast-feeding. J Pediatr 115: 336-337, 1989.
• J Pediatr 114: 476-478, 1989. No Abstract on-line.
  Schimmel M, Eidelman AJ, Wilschanski MA, Shaw D, Ogilvie R, Koren G: Toxic effects of atenolol consumed during breast-feeding.
• Ann Pharmacother 27: 40-42, 1993.
  Ito S, Koren G, Einarson TR: Maternal noncompliance with antibiotics during breast-feeding.
• Br J Clin Pharmacol 38: 99-102, 1994.
  Ito S, Koren G: A novel index for expressing exposure of the infants to drugs in breast milk.
• Am J Obstet Gynecol, 172: 881-886, 1995.
  Ito S, Moretti M, Chu M, Koren G: Initiation and duration of breast-feeding in women receiving antiepileptics.
• 
  Matsui D, Koren G: Drug transfer into human milk, Pediatric pathophysiology, (Gluckman & Heymann, eds). Edward Arnold, ltd, London (In Press).
• Ann Pharmacother 28: 585-587, 1994.
  Taddio A, Klein J, Koren G: Acyclovir excretion in human breast milk
• J Clin Toxicol 28: 365-370, 1990.
  Robieux I, Koren G, Wandenberg H, Schneiderman J: Morphine excretion in breastmilk and resultant exposure in a nursing infant.
• J Clin Pharmacol 36: 42-47, 1996.
  Taddio A, Ito S, Koren G: Excretion of fluoxetine and its metabolite in human breast milk.
• Am J Obstet Gynecol 173: 1625-1626, 1995.
  Moretti M, Ito S, Koren G: Disposition of ketoconazole in human milk
• Reprod Toxicol 9: 153-157, 1995.
  Taddio A, Ito S, Einarson T, Leeder JS, Koren G: Effect of counseling on maternal reporting of adverse effects in nursing infants exposed to antibiotics through breast milk.
• J Hum Lact 2000 Aug;16(3):229-30.
  Bar-Oz B, Ito S, Parks V, Maurer MP, Koren G: Estimation of neonatal exposure after accidental ingestion of lufenuron in a breastfeeding mother.
• Biol Neonate 2001; 80: 219-22.
  Ho E, Collantes A, Kapur BM, Moretti M, Koren G: Alcohol and breastfeeding: calculation of time to zero level in milk