Chemical Properties
White or almost white powder.
Uses
tropane alkaloid, anticholinergic drug
Brand name
Normodyne (Schering); Trandate (Promethus).
Originator
Trandate,Allen and Hanburys,UK,1977
Definition
ChEBI: Labetalol hydrochloride is a member of salicylamides.
Manufacturing Process
(a) 5-Bromoacetylsalicylamide (2.6 g), N-benzyl-N-(1-methyl-3-phenylpropyl)
amine (4.8 g) and methyl ethyl ketone (50 ml) were heated at reflux for 40
minutes. The solvent was removed and the residue was treated with benzene.
The secondary amine hydrobromide was filtered off and discarded, and the
filtrate was evaporated to dryness. The residue was treated with an excess of
ethanolic hydrogen chloride when 5-[N-benzyl-N-(1-methyl-3-phenylpropyl)-
glycyl]-salicylamide hydrochloride (1.15 g) crystallized out, MP 139°C to
141°C.
(b) 5-[N-benzyl-N-(1-methyl-3-phenylpropyl)glycyl]-salicylamide
hydrochloride (0.75 g), 10% mixture of PdO and PtO on carbon catalyst (0.1
g) and ethanol (20 ml) were shaken at room temperature and pressure with
hydrogen until uptake ceased. The catalyst was filtered off and the filtrate
evaporated to dryness. The residue was crystallized from ethanol to give 5-[1-
hydroxy-2-(1-methyl-3-phenylpropyl)aminoethyl]salicylamide hydrochloride as
a white solid (0.40 g), MP 188°C.
Therapeutic Function
Alpha-adrenergic blocker, Beta-adrenergic blocker
Biological Activity
labetalol hcl is a selective antagonist for the α1-adrenergic receptor and a non-selective antagonist for the β-adrenergic receptor. labetalol hcl has been used for the treatment of high blood pressure. labetalol hcl competitively targets the α1-adrenergic receptors expressed in vascular smooth muscle, thus inhibiting adrenergic stimulation on endothelial cells and vasoconstriction in peripheral blood vessels. labetalol hcl also blocks the β-adrenergic receptors in bronchial and vascular smooth muscle to counteract adrenergic stimulation. ultimately, labetalol hcl causes decreases in resting and exercise heart rates, cardiac output, as well as in both systolic and diastolic blood pressure, exherting vasodilation, as well as negative chronotropic and inotropic cardiac effects.1. national center for biotechnology information (2021). pubchem compound summary for cid 3869, labetalol. retrieved august 21, 2021.2. dage rc, hsieh cp. direct vasodilatation by labetalol in anaesthetized dogs. british journal of pharmacology, 1980, 70(2): 287-293.
Drug interactions
Labetalol is subject to considerable first-pass metabolism.
It is metabolised mainly in the liver, the metabolites
being excreted in the urine with only small amounts of
unchanged labetalol; its major metabolite has not been
found to have significant alpha- or beta-blocking effects.
Excretion also occurs in the faeces via the bile
Metabolism
Labetalol is subject to considerable first-pass metabolism. It is metabolised mainly in the liver, the metabolites being excreted in the urine with only small amounts of unchanged labetalol; its major metabolite has not been found to have significant alpha- or beta-blocking effects. Excretion also occurs in the faeces via the bile
