Metronidazole Hydrochloride

An anti-infective agent from the imidazole family, indicated for the treatment of giardiasis, amoebiasis, trichomoniasis and anaerobic infections (Bacteroides and Clostridium). Administered orally once to three times a day. Intravenous administration is used in severe cases.

It is excreted into breast milk in moderate but clinically insignificant amounts. ^{(van Wattum 2019, Geballa 2018, Zhang 1997, Passmore 1988, Heisterberg 1983, Erickson 1981, Gray 1961)} The relative paediatric dose may reach 10.6%. ^{(van Wattum 2019)}

No problems have been observed in infants whose mothers were taking the drug ^{(Passmore 1988, Heisterberg 1983, Gray 1961)}, apart from one possible case of diarrhoea and secondary lactose intolerance. ^{(Clements 1980)} Plasma levels in these infants are undetectable or very low. ^{(Passmore 1988, Heisterberg 1983, Gray 1961)}

Metronidazole may discolour bodily fluids red and give the milk a bitter or metallic taste ^{(Chin 2001, Andersson 1981)}, although this is not harmful.

There are older studies which demonstrated carcinogenic effects in rats given high doses. This has not been demonstrated in humans ^{(Falagas 1998, Fahrig 1997, Beard 1988, Roe 1985)}, and there remains considerable controversy ^{(Adil 2018, Friedman 2009)}; metronidazole is one of the most widely used antibiotics for vaginal, intestinal and other infections, and its use in humans is becoming increasingly widespread. ^{(Adil 2018, Sobel 2015)}

Approved and widely used in paediatrics. The dose for infants under two months is 15 mg/kg/day and for those over two months, 30 mg/kg/day. ^{(AEMPS 2026)}

Although opinions are divided ^{(Huang 2016)}, and it is contraindicated for some ^{(van der Woude 2015 and 2010, Nielsen 2014, Yarur 2013)}, various medical societies, experts and expert consensus groups consider the use of this medication during breastfeeding to be safe ^{(Hale 2017, Schulze 2014, Kong 2013, Rowe 2013, Bar-Oz 2003, Einarson 2000, Rubin 1986)}, with some authors recommending that, where the dose is high, breastfeeding should be delayed for 12 to 24 hours following administration of a single 2g dose in order to minimise exposure. ^{(Workowski 2021, Damas 2015, Huang 2014, Rowe 2013, CDC 2010, WHO 2002)}
In the case of the mother of a premature or newborn baby, who metabolise metronidazole less effectively, it may be prudent either to use the minimum effective dose or to choose an alternative.

See below the information of this related product:

• Metronidazole (Dermal and Vaginal use) (Safe product and/or breastfeeding is the best option.)