α1-adrenergic receptor; β-adrenergic receptor
α1-Adrenergic receptor [] [1]
- β1-Adrenergic receptor [] [1]
- β2-Adrenergic receptor [] [1]

Due to significant first-pass metabolism, the oral bioavailability of labetalol hydrochloride (AH-5158 HCl; Sch-15719W) in humans is approximately 25%–40%[1]. The plasma half-life (t1/2) of this drug in humans is 3–6 hours[1]. Labetalol hydrochloride is widely distributed throughout the body, with a volume of distribution of approximately 9–12 L/kg[1]. It is mainly metabolized in the liver via glucuronide conjugation, and its metabolites are mainly excreted in urine (60%–70%) and feces (30%–40%)[1].

Effects During Pregnancy and Lactation
◉ Overview of Lactation Use
Because the amount of labetalol in breast milk is low, the amount ingested by the infant is very small, and no adverse effects are expected on full-term breastfed infants. Most infants require no special attention. However, other medications may be more suitable when breastfeeding preterm infants.
Labetalol may make breastfeeding mothers more susceptible to nipple Raynaud's phenomenon.
◉ Effects on Breastfed Infants
One researcher reported that breastfed infants whose mothers took 330 to 800 mg of labetalol daily did not experience adverse reactions.
A preterm infant born at 26 weeks gestation, weighing 640 grams, developed sinus bradycardia (80 to 90 beats/min) and isolated premature atrial contractions after being fed expressed breast milk via nasogastric tube on day 8 after birth. The mother was taking labetalol orally at 300 mg twice daily for hypertension. After replacing breast milk with formula for 24 hours, bradycardia and premature beats disappeared. No other cause of bradycardia was found. One mother's breast milk sample (not collected at a fixed time) contained 710 mcg/L of labetalol. Although the authors estimated the infant's daily dose to be 100 mg/kg, recalculation based on their data revealed that the actual dose was only 100 mcg/kg. A 2-month-old infant was exclusively breastfed by a mother taking 100 mg of labetalol twice daily. The infant's ECG showed a normal heart rate but a slightly prolonged QT interval. The infant was started on propranolol 1 mg/kg once daily due to an infantile hemangioma. After one month, the infant's QT interval returned to normal. Another infant was exclusively breastfed by a mother taking 150 mg of labetalol twice daily and nifedipine 60 mg once daily. The infant was started on propranolol 0.6 mg/kg once daily due to an infantile hemangioma. The dose of propranolol was increased to 3.4 mg/kg once daily within two weeks. Infants experienced sleep difficulties after receiving higher doses of propranolol, but without other symptoms.
◉ Effects on Lactation and Breast Milk
Intravenous labetalol can increase serum prolactin levels in men and non-lactating women, but the increase is greater in women. Oral labetalol does not increase serum prolactin levels. Prolactin levels in established lactating mothers may not affect their ability to breastfeed.
A woman with a history of Raynaud's phenomenon experienced nipple Raynaud's phenomenon while receiving labetalol 100 mg twice daily for gestational hypertension. She breastfed for 5 weeks, but breastfeeding caused nipple pain. Similar symptoms occurred during subsequent pregnancies while receiving labetalol 100 mg twice daily. The nipple pain disappeared after both withdrawals of labetalol.
A pregnant woman received intravenous labetalol twice for preeclampsia. Each time, she reported a burning sensation in her nipples. While continuing to take labetalol, she added sustained-release nifedipine to her treatment regimen, and the nipple burning sensation did not reappear.

---

The plasma protein binding rate of labetalol hydrochloride is approximately 50%[1]
- Common adverse reactions in humans include orthostatic hypotension (reported in 5-10% of patients), dizziness (8%), fatigue (6%), nausea/vomiting (4%), and diarrhea (3%)[1]
- Rare toxic reactions include hepatocellular damage (incidence <0.1%), with isolated cases reporting elevated serum ALT and AST levels; these abnormalities are usually reversible upon discontinuation of the drug[1]
- No significant nephrotoxicity has been observed in clinical use, nor have there been any sustained changes in serum creatinine or blood urea nitrogen levels[1]
- Labetalol hydrochloride may interact with other antihypertensive drugs, enhancing their antihypertensive effect; co-administration with nonsteroidal anti-inflammatory drugs (NSAIDs) may reduce their antihypertensive efficacy[1]
- Overdose may lead to severe hypotension, bradycardia, and bronchospasm, requiring supportive treatment such as intravenous fluids and vasopressors[1]

[1]. Expert Opin Drug Saf . 2015 Mar;14(3):453-61.

Labetalol hydrochloride belongs to the salicylamide class of drugs. Labetalol hydrochloride is the hydrochloride salt form of labetalol, a third-generation selective α1-adrenergic receptor antagonist and a non-selective β-adrenergic receptor antagonist with vasodilatory and hypotensive effects. Labetalol competitively binds to α1-adrenergic receptors in vascular smooth muscle, thereby inhibiting adrenergic stimulation of endothelial cell function and vasoconstriction of peripheral blood vessels. The drug also binds to β-receptors in bronchial and vascular smooth muscle, leading to attenuated adrenergic stimulation. The result is a decrease in resting and exercise heart rate, cardiac output, and both systolic and diastolic blood pressure, leading to vasodilation and producing negative chronotropic and inotropic cardiac effects. It is a salicylamide derivative and a non-cardiac selective blocker of both β-adrenergic and α-1-adrenergic receptors. See also: labetalol (with active fraction); hydrochlorothiazide; labetalol hydrochloride (component).

---

Labetalol hydrochloride is an α1-adrenergic receptor blocker and a non-selective β-adrenergic receptor blocker (α1:β blocking ratio is approximately 1:7)[1]
- Its antihypertensive mechanism includes reducing peripheral vascular resistance through α1 blockade and reducing cardiac output and renin release through β1/β2 blockade[1]
- Clinically, it is indicated for the treatment of hypertension, including essential hypertension, hypertensive emergencies, and gestational hypertension (pregnancy-related medication is classified as Category C; no fetal risk has been found in animal studies, but human data are limited)[1]
- The drug is available in oral (tablet) and intravenous formulations; the oral dose is usually 100 mg twice daily to 800 mg twice daily; the intravenous dose is 20-80 mg as a single bolus or continuous infusion at a rate of 0.5-2 mg/min[1]
- Compared with other beta-blockers, it is less likely to cross the blood-brain barrier, thus minimizing central nervous system side effects [1]

C19H25CLN2O3

364.866404294968

364.16

C, 62.55; H, 6.91; Cl, 9.72; N, 7.68; O, 13.15

32780-64-6

Labetalol; 36894-69-6; Labetalol hydrochloride (Standard); 32780-64-6

71412

White to off-white crystalline powder

1.2±0.1 g/cm3

552.7±50.0 °C at 760 mmHg

187-189°

288.1±30.1 °C

0.0±1.6 mmHg at 25°C

1.609

2.31

5

4

8

25

385

0

O=C(N)C1=CC(C(O)CNC(C)CCC2=CC=CC=C2)=CC=C1O.[H]Cl

WQVZLXWQESQGIF-UHFFFAOYSA-N

InChI=1S/C19H24N2O3.ClH/c1-13(7-8-14-5-3-2-4-6-14)21-12-18(23)15-9-10-17(22)16(11-15)19(20)24;/h2-6,9-11,13,18,21-23H,7-8,12H2,1H3,(H2,20,24);1H

2-hydroxy-5-[1-hydroxy-2-(4-phenylbutan-2-ylamino)ethyl]benzamide;hydrochloride

AH-5158 hydrochloride; Sch-15719W; AH5158 hydrochloride; Sch15719W; AH 5158 hydrochloride; Sch 15719W; Normodyne; Trandate; Albetol; Apo-Labetalol; Dilevalol

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Note: Please store this product in a sealed and protected environment (e.g. under nitrogen), avoid exposure to moisture and light.

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

Solubility in Formulation 1: ≥ 2.5 mg/mL (6.85 mM) (saturation unknown) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 400 μL PEG300 and mix evenly; then add 50 μL Tween-80 to the above solution and mix evenly; then add 450 μL normal saline to adjust the volume to 1 mL.
Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

---

Solubility in Formulation 2: ≥ 2.5 mg/mL (6.85 mM) (saturation unknown) in 10% DMSO + 90% (20% SBE-β-CD in Saline) (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 900 μL of 20% SBE-β-CD physiological saline solution and mix evenly.
Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.

---

View More

Solubility in Formulation 3: ≥ 2.5 mg/mL (6.85 mM) (saturation unknown) in 10% DMSO + 90% Corn Oil (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 900 μL of corn oil and mix evenly.

---

 (Please use freshly prepared in vivo formulations for optimal results.)