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Drugs and Lactation Database (LactMed®) [Internet]. Bethesda (MD): National Institute of Child Health and Human Development; 2006-.
CASRN: 61-32-5
Drug Levels and Effects
Summary of Use during Lactation
Amounts of methicillin ingested by the infant in breastmilk are small and would not be expected to cause any adverse effects. Occasionally disruption of the infant's gastrointestinal flora, resulting in diarrhea or thrush have been reported with penicillins, but these effects have not been adequately evaluated. Methicillin is acceptable in nursing mothers.
Drug Levels
Maternal Levels. Intramuscular injections of methicillin 1 gram every 6 hours for 6 to 9 days in 17 women with monolateral mastitis yielded methicillin levels in milk that reached a peak of 0.31 mg/L at 3 hours after the first dose on the first day in the healthy breast, and much lower levels in the breast with mastitis. After the last dose, peak milk levels of 1.53 mg/L occurred 6 hours after the dose. Methicillin milk levels from both breasts were equal.[1]
After a single intramuscular dose of 1 gram of methicillin in 3 women, milk levels ranged from 0.2 to 0.3 mg/L between 1 and 6 hours.[2]
Infant Levels. Relevant published information was not found as of the revision date.
Effects in Breastfed Infants
Relevant published information was not found as of the revision date.
Effects on Lactation and Breastmilk
Relevant published information was not found as of the revision date.
Alternate Drugs to Consider
(Methicillin-sensitive Staph. aureus) Cefazolin, Cephalexin, Dicloxacillin, Floxacillin, Oxacillin, Nafcillin; (Methicillin-resistant Staph. aureus) Doxycycline, Linezolid, Minocycline, Trimethoprim-Sulfamethoxazole, Vancomycin
References
- 1.
- Kulakov VI, Zak IR, Kulikova NN, et al. Body pharmacokinetics of methicillin, oxacillin and cephaloridine in puerperal mastitis. Antibiotiki 1981;26:110-3. [PubMed: 7212690]
- 2.
- Matsuda S. Transfer of antibiotics into maternal milk. Biol Res Pregnancy Perinatol 1984;5:57-60. [PubMed: 6743732]
Substance Identification
Substance Name
Methicillin
CAS Registry Number
61-32-5
Drug Class
Breast Feeding
Lactation
Milk, Human
Anti-Infective Agents
Antibacterial Agents
Penicillins
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