5-[1-Hydroxy-2-(1-methyl-3-phenylpropylamino)ethyl]salicylamide hydrochloride

Labetalol is a non-cardioselective beta-blocker used in the treatment of hypertension, stable chronic angina pectoris, sympathetic overactivity syndrome associated with severe tetanus, the control of blood pressure in patients with pheochromocytoma, preeclampsia in pregnant women and to produce controlled hypotension during anesthesia in order to reduce bleeding resulting from surgical procedures. Administration is carried out orally in 2 daily doses or intravenously for the emergency treatment of hypertension.

Despite not having high protein binding ^{(Riant 1986)}, other pharmacokinetic properties (moderate liposolubility and high volume of distribution) probably explain why labetalol is excreted in breastmilk in clinically insignificant amounts. ^{(Hale, Anderson 2018, FDA 2010, Atkinson 1990 and 1988, Lunell 1985, Michael 1979)}

In addition, its low oral bioavailability hinders its transfer to infant plasma from breastmilk, except in premature babies and the immediate neonatal period when there may be increased intestinal permeability.

No problems have been observed in term infants whose mothers were prescribed labetalol during breastfeeding ^{(Aizman 2020, Briggs 2015, AEMPS 2001, Michael 1979)}. A poorly documented case of asymptomatic bradycardia has been recorded (poster) in an extremely premature baby of 26 weeks of gestation with 640g birth weight, whose mother took 600 mg of labetalol per day. Through breastmilk, the baby received 0.1 mg/kg /day of labetalol, which is 1% of the maternal dose and 0.8% of the pediatric dose. (Mirpuri 2008).

Plasma levels of breastfed babies whose mothers took labetalol were very low. ^{(Lunell 1985, Michael 1979)}.

Oral labetalol does not affect the secretion of prolactin ^{(Barbieri 1982)}. Labetalol has been associated with neonatal hypoglycemia during pregnancy or delivery, but not during breastfeeding. (Munshi 1992). The use of labetalol for the treatment of hypertension during pregnancy has been associated with Raynaud's phenomenon and nipple pain during breastfeeding ^{(Avila 2019, McGuinness 2013)}. Discontinuing labetalol eliminated the pain.

Some authors do not consider beta-blockers to be drugs of choice for the treatment of hypertension, unless there is another indication simultaneously, such as migraine or the prophylaxis of angina. ^{(Anderson 2018)}

Several medical associations, experts and expert consensus believe its use to be safe or probably safe during breastfeeding. (Hale, Briggs 2015, Serrano 2014, Davanzo 2014, Rowe 2013, Podymow 2011, Ghanem 2008). The American Academy of Pediatrics considers labetalol to be generally compatible with breastfeeding. ^{(AAP 2001)}