Local anaesthetics are quite widely used in society from repairing the damaged perineum in childbirth to tooth fillings and extractions as well as biopsies of the breast.
I find it fascinating that women are still advised to interrupt breastfeeding for a period after the injection. If you think about this from a common sense point of view we know that only the very local area around the injection is numbed. If the dentist injects into your gum, your arm doesn’t become numb? Which supports why there is no need to stop breastfeeding for even a moment because it doesn’t get absorbed from milk.
Having said that one women who contacted me had been told by her dentist that if she continued to feed her baby would damage her nipples as the mouth would be numb!
Local anaesthetics are also included in lozenge and sprays for sore throats https://breastfeeding-and-medication.co.uk/fact-sheet/sore-throat-tonsilitis-and-breastfeeding and these are compatible with breastfeeding.
Some practitioners are concerned that injecting into the breast during a biopsy makes it more likely that the anaesthetic will more likely be absorbed into the milk due to proximity to the milk ducts. There is no evidence for this and the most important pharmacokinetic factor is that the drug is poorly bio-available and generally have a short half life.
Local anaesthetics may also be included with steroids in injections into joints which are also compatible with breastfeeding.
Benzocaine (taken from Hale online access):
temporarily relieves pain associated with minor cuts, minor burns, itching. There are no adequate and well-controlled studies or case reports in breastfeeding women. Due to its poor bioavailability after topical application, concentrations achieved in maternal plasma are probably too low to produce any significant clinical effects in the breastfed infant. Dental procedure benzocaine usage is minimal and should pose no harm to the breastfed infant. Maternal plasma and milk levels do not seem to approach high concentrations and the oral bioavailability in the infant would be quite low (<35%).
Lidocaine
Oral bioavailability <35% https://www.e-lactancia.org/breastfeeding/lidocaine/product/ and compatible with topical application
BNF “Present in milk but amount too small to be harmful.”
