Labetalol  

Labetalol
Systematic (IUPAC) name
(RS)-2-hydroxy-5-{1-hydroxy-2-[(1-methyl-3-phenylpropyl)amino]ethyl}benzamide
Identifiers
CAS number	36894-69-6
ATC code	C07AG01
PubChem	3869
DrugBank	APRD01062
ChemSpider	3734
Chemical data
Formula	C19H24N2O3
Mol. mass	328.406 g/mol
SMILES	eMolecules & PubChem
Pharmacokinetic data
Bioavailability	90-100%
Protein binding	50%
Metabolism	hepatic pass metabolism,
Half life	Tablet: 6-8 hours; IV: 5.5 hours
Excretion	Excreted in urine, not removed by hemodialysis
Therapeutic considerations
Pregnancy cat.	C One of few drugs used for PIH
Legal status	Prescription only
Routes	oral iv
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Labetalol (Normodyne, Trandate, fixed combination with hydrochlorothiazide: Normozyde) is a mixed alpha/beta Adrenergic antagonist, which is used to treat high blood pressure.^[1]

Chemistry

Labetalol has stereoisomers.^[2] It a racemic mixture of four isomers. Two of these isomers, the (S,S)- and (R,S)- forms are inactive. The third, the (S,R)-isomer, is a powerful ₁ blocker. The fourth isomer, the (R,R)-isomer, is a mixed nonselective blocker and selective ₂ agonist.

It works by blocking these adrenergic receptors, which decreases peripheral vascular resistance without significantly altering heart rate or cardiac output. The : antagonism of Labetalol is approximately 3:1.^[3][4]

Indications

It has a particular indication in the treatment of pregnancy-induced hypertension which is commonly associated with pre-eclampsia. ^[5]

It is also used to treat chronic hypertension of pheochromocytoma and hypertensive crisis.^[3]

Administration

Labetalol is available in 100, 200, and 300 mg tablets and intravenously (only as Trandate) in 5 mg/ml solution. Adults taking tablets usually start with 100 mg twice daily, with a maximum of 2.4 g/day. In cases of emergency dosage might be higher. IV doses are usually started at 20mg over 2 minutes. Additional doses of 40mg, then 80mg may be administered every ten minutes as needed. Additional 80mg doses can be given to a total maximum dose of 300 mg. Additionally, labetalol can be administered by IV infusion at a rate of 2mg/minute, with a maximum dose of 300mg.

Side effects

Side effects may include:

• Drowsiness
• Fatigue
• Weakness
• Difficulty sleeping
• Diminished sexual function
• Scalp tingling which passes after time.
• A rare but potentially lethal side effect is respiratory distress.

Contraindications

Labetalol has relative contraindications for use in patients with asthma, congestive heart failure, any degree of heart block, bradycardia, or those in cardiogenic shock.

References

Recent Labetalol Forums  View All  

Labetalol Is Superior Than Methyldopa labetalol is alpha and beta blocker both as well as fast onset of action and renal impairement Thursday, 4/16/2009 2:07:50 AM  Post a Reply

First Time User just nervous about taken this medication even though it was prescribed by my doctor,has anyone had serious problems using this medicine? Tuesday, 6/20/2006 11:17:17 AM  2 Replies