Labetalol – A Dual-Action Antihypertensive Drug

 

Table of Contentsm: 

1. Introduction  

2. Mechanism of Action  

3. Pharmacokinetics & Pharmacodynamics  

4. Indications & Drug of Choice  

5. Contraindications  

6. Side Effects  

7. Dosage  

8. Brand Names  

9. Price  

10. Conclusion  

1. Introduction:

*Labetalol* is a unique antihypertensive drug that acts as both a *non-selective beta-blocker* and a *selective alpha-1 blocker*. It is used for both *chronic hypertension* and *hypertensive emergencies*, including during *pregnancy (preeclampsia)* where it is considered *safe and effective*.

2. Mechanism of Action:

- *Beta-1 & Beta-2 receptor blockade* → ↓ heart rate and cardiac output

- *Alpha-1 receptor blockade* → vasodilation → ↓ peripheral resistance  

This dual action leads to *rapid and sustained blood pressure reduction* without reflex tachycardia.

 

3. Pharmacokinetics & Dynamics:

| Onset            | 20–120 min             | 2–5 min                

| Peak             | 1–4 hours              | 5–15 min               

| Half-life        | 6–8 hours              | Similar                

| Metabolism       | Liver (extensive first-pass) 

| Excretion        | Urine & feces          |

4. Indications & Drug of Choice:

*Indications*

- *Chronic hypertension*

- *Hypertensive emergencies*

- *Hypertension in pregnancy* (preeclampsia/eclampsia)

- *Post-operative hypertension*

- *Aortic dissection (IV form)*

*Drug of Choice For:*

- *Severe hypertension in pregnancy*

- *Hypertensive crisis (with tachycardia)*

- *Aortic dissection (along with nitroprusside)*

5. Contraindications:

- Asthma or chronic bronchospasm  

- Bradycardia  

- AV block >1st degree  

- Overt cardiac failure  

- Cardiogenic shock  

- Severe hepatic impairment  

6. Side Effects:

*Common:*

- Dizziness

- Fatigue

- Nausea

- Postural hypotension

*Serious:*

- Bronchospasm (especially in asthma patients)

- Bradycardia

- Hepatotoxicity (rare)

- Heart block

7. Dosage:

*Oral (Hypertension):*

- Start: *100 mg twice daily*

- Max: *2400 mg/day* (divided doses)

*IV (Hypertensive Emergency):*

- *Bolus*: 20 mg over 2 mins, may repeat with 40–80 mg every 10 mins  

- *Infusion*: 0.5–2 mg/min (titrate)

*In pregnancy (oral):*

- 100–200 mg twice or thrice daily

8. Brand Name:

- *Normodyne*  

- *Trandate*  

- *Presolol*  

- *Labetamed*  

- *Labetaloc*  

- *Lobet*  

9. Price:

- *Pakistan*: PKR 15–60 per tablet (100–200 mg)  

- *India*: INR 5–20/tablet  

- *USA*: 1–5 per tablet (generic), ~$15–30 per ampule (IV)

10. Conclusion:

*Labetalol* is a powerful antihypertensive that offers *dual benefit* through *alpha and beta blockade*, making it ideal for both emergency and chronic blood pressure control. It is especially *favored in pregnancy and hypertensive crises*, offering rapid BP reduction with a safe profile. However, caution is needed in patients with *asthma, bradycardia, or heart block*.