Drugs and their categories in pregnancy and breastfeeding-M

Drug	Pregnancy category	Compatibility with breastfeeding
macrogol	unlisted	compatible
macrogol 3350	unlisted	compatible
magnesium hydroxide	A	compatible
magnesium sulfate	unlisted	compatible
maldison	B2	caution, insufficient data
mannitol	unlisted	compatible
mebendazole	B3	compatible
mebeverine	B2	caution, insufficient data
medroxyprogesterone acetate	IM contraceptive dose: A oral high dose 30-50mg and IM high dose: D	IM contraceptive dose: compatible oral high dose 30-50 mg and IM high dose: compatible from 6 weeks postpartum
mefenamic acid	C	compatible [Note 10]
mefloquine	B3	caution, monitor infant for adverse effects
meloxicam	C	caution, insufficient data, consider alternative [Note 10]
mepivicaine	A	caution, insufficient data
mepivicaine with adrenaline	A	caution, insufficient data
mercaptopurine	D	avoid
meropenem	B2	caution, insufficient data
mesalazine	C	caution; may cause diarrhoea in infant
mestranol	B3	avoid, reduced milk supply
metaraminol	C	caution, insufficient data
metformin	C	compatible
methadone	C	compatible
methdilazine	B2	avoid
methotrexate	D	avoid
methoxsalen	systemic and topical use: B2	systemic and topical use: avoid, insufficient data
methoxyflurane	C	insufficient data
methyl salicylate	topical: unlisted	topical: compatible
methylcellulose	unlisted	compatible
methyldopa	A	compatible
methylene blue	unlisted	caution, insufficient data
methylphenidate	B2	insufficient data
methylprednisolone aceponate	topical use: C	topical use: compatible; avoid use on nipples
methylprednisolone acetate	depot injection: C	depot injection: compatible
methylprednisolone sodium succinate	systemic use: C	systemic use: compatible, caution with high pulse doses
methysergide	C	avoid, insufficient data
metoclopramide	A	compatible
metoprolol	C [Note 13]	compatible
metronidazole	systemic use: B2 topical use: B2	systemic use: compatible; avoid high single-dose therapy topical use: compatible
metyrapone	B2	avoid, insufficient data
mexiletine	B1	compatible
mianserin	B2 [Note 2]	insufficient data
miconazole	topical use: A	topical use: compatible
midazolam	C	compatible in single dose
midodrine	unlisted	caution, insufficient data
milrinone	B3	caution, insufficient data
minocycline	D	avoid if possible, possibility of staining infant's teeth with prolonged courses
minoxidil	oral use: C topical use: C	oral use: caution, insufficient data topical use: compatible
mirtazapine	B3	insufficient data
misoprostol	X	caution, insufficient data
mitozantrone	D	avoid
moclobemide	B3	compatible
modafinil	B3	avoid, insufficient data
mometasone furoate	B3	compatible
montelukast	B1	caution, insufficient data
morphine	C	compatible in usual analgesic doses used in the perinatal period; caution with high-dose extended-release preparations, as there are no data
moxifloxacin	B3	avoid, insufficient data
moxonidine	B3	avoid, insufficient data
mupirocin	B1	compatible
mycophenolate mofetil	D	avoid, insufficient data

Note 1: In Australia, breastfeeding is not recommended for HIV-positive women because of the possibility of HIV transmission. Note 2: Human data are inadequate and the safety of these medications in pregnancy is uncertain. Note 3: Antiandrogens have the potential to feminise the male fetus, avoid in pregnancy. Note 4: Tetracyclines are safe for use during the first 18 weeks of pregnancy (16 weeks postconception) after which they may affect the formation of the baby's teeth and cause discolouration. Note 6: Tricyclic antidepressants have been taken by a large number of pregnant women without any proven increase in the frequency of fetal malformation. In full-term neonates, reversible adverse effects have occasionally been observed, but very rarely cause significant problems. Note 7: Although theophylline has a Category A rating, it does cross the placental barrier. The effect on fetal development is not known. Theophylline clearance is significantly decreased in premature infants. Therefore, if this drug is administered to the mother near the time of delivery, the neonate should be monitored closely for the pharmacological effects of theophylline. Hence the use of theophylline in pregnant women should be balanced against the risk of uncontrolled asthma. Note 8: See also: Cleland LG, James MJ, Proudman SM. Fish oil: what the prescriber needs to know. Arthritis Research and Therapy 2006;8(1):202-11. Note 9: See leflunomide regarding preconception advice and cholestyramine washout. Note 10: If an NSAID is required in a breastfeeding patient, diclofenac or ibuprofen is preferred. Note 11: Absorption of eye drops into the maternal circulation is generally low, although there are occasional reports of systemic effects. Nevertheless, significant transfer into milk is unlikely. Note 12: Large molecular weight proteins/polypeptides are unlikely to transfer into milk. In the absence of specific information, adverse effects in the infant are unlikely. Note 13: Early reports of pregnancy outcomes in women treated with beta blockers in pregnancy, particularly dealing with propranolol, described a relatively high incidence of fetal growth restriction. This appears to be the basis for the C classification of the class of drugs. Since these findings were not from randomised studies, but were clinical descriptions of women who had underlying disorders known to be associated with an increased rate of both intrauterine fetal growth restriction and death, it is not possible to determine whether the described outcomes were due to the therapy or to the disorder for which therapy was prescribed. Subsequent evidence has indicated fetal growth restriction in hypertensive pregnant women treated with atenolol, but better fetal growth in women treated with another beta blocker, oxprenolol, than in women treated with methyldopa. This has been attributed to the intrinsic sympathomimetic activity inherent in this drug. No other fetal or neonatal problems have been attributed to beta-blocker therapy in pregnancy, and they are widely prescribed for the treatment of hypertension in this situation.