Labetalol (Trandate) | Medication Reference

Bedside Snapshot

IV labetalol is a mixed alpha-1 and nonselective beta-blocker used for rapid blood pressure control in many hypertensive emergencies, especially when you want to lower BP without big changes in heart rate or cardiac output.

Effects: Decreases systemic vascular resistance via alpha-1 blockade and blunts reflex tachycardia via beta-1 blockade. Bronchospasm is possible via beta-2 blockade, so avoid in reactive airway disease.
Onset (IV): 1–5 minutes; peak around 5–15 minutes; duration 2–4 hours after bolus, making it useful for sustained but titratable BP control.
Typical adult IV bolus dosing: 20 mg IV over 2 minutes initially; then 40–80 mg IV every 10 minutes until target BP, up to a total of 300 mg. Alternative: start 1–2 mg/min infusion, titrating to effect (max cumulative ~300 mg).
Pregnancy/preeclampsia: 10–20 mg IV over 2 minutes, then 20–80 mg IV every 10–30 minutes to a maximum total dose of 300 mg, or continuous infusion 1–2 mg/min.
Avoid in: Asthma, bradycardia, heart block, or decompensated heart failure.

Brand & Generic Names

Generic Name: Labetalol hydrochloride
Brand Names: Trandate (IV, some regions), various generics (IV/PO); availability is institution-specific

Medication Class

Mixed alpha-1 and nonselective beta-adrenergic blocker (beta > alpha); intravenous antihypertensive

Pharmacology

Mechanism of Action:

Nonselective beta-adrenergic blocker (beta-1 and beta-2) with concurrent competitive alpha-1 adrenergic antagonism. The beta:alpha blocking ratio is roughly 7:1 IV and 3:1 orally.
Beta-1 blockade decreases heart rate, myocardial contractility, and renin release, reducing cardiac output and RAAS activation.
Alpha-1 blockade causes vasodilation of arterioles and veins, reducing systemic vascular resistance and BP, with relatively less reflex tachycardia than pure vasodilators.
Beta-2 blockade may lead to bronchoconstriction and can blunt beta-agonist response in bronchospastic disease, so IV labetalol is generally avoided in significant asthma or COPD with active bronchospasm.
The combined alpha and beta blockade can be advantageous in hyperadrenergic states, theoretically reducing concern for unopposed alpha stimulation seen with pure beta-blockade.

Pharmacokinetics:

Onset (IV): BP reduction begins within 1–5 minutes after a bolus; maximal effect typically within 5–15 minutes
Duration: 2–4 hours after a typical IV bolus, depending on dose; longer with larger cumulative doses or infusions
Distribution: Moderate protein binding (~50%); large volume of distribution with extensive tissue uptake
Metabolism: Hepatic metabolism primarily via conjugation to inactive glucuronide metabolites
Elimination: About 55–60% recovered in urine (mostly as metabolites) and 20–30% in feces. Less than 5% excreted unchanged in urine
Half-life: Terminal elimination half-life after IV is roughly 5–6 hours (range ~2.5–8 hours), but clinical BP effect is shorter due to redistribution
Hepatic impairment: Can prolong half-life and increase drug exposure; use lower doses and titrate carefully

Indications

Hypertensive emergency/urgency where controlled BP reduction is required (e.g., encephalopathy, intracranial hemorrhage, ischemic stroke with BP above treatment threshold, severe hypertension with end-organ injury)
Acute severe hypertension in pregnancy and postpartum (preeclampsia/eclampsia, HELLP) as a first-line IV agent alongside hydralazine and nifedipine in many guidelines
Aortic dissection (as a beta-blocker option) to rapidly reduce shear stress by lowering heart rate and BP; often combined with a vasodilator once beta blockade is established
Perioperative and postoperative hypertension when heart rate control is acceptable and beta-blockade is not contraindicated
Hypertensive crises associated with sympathetic excess or stimulant toxicity (e.g., certain cases of cocaine/amphetamine toxicity) when alpha blockade is desired; institutional practice varies and evidence is limited

Dosing & Administration

Available Forms:

IV injection: typically 5 mg/mL in vials or ampules (e.g., 20 mL vial containing 100 mg labetalol)
IV premixed bags: institution-specific concentrations (e.g., 200 mg in 250 mL or similar for infusion)
Oral tablets (for step-down/chronic therapy): commonly 100 mg, 200 mg, and 300 mg strengths

Standard Adult Dosing:

Clinical Scenario	Dose & Route	Frequency / Titration	Notes
Hypertensive emergency (non-pregnant adult) – bolus strategy	20 mg IV over 2 min initially; then 40–80 mg IV bolus	Repeat q10 min as needed; max total ~300 mg	Aim to reduce BP by ~20–25% in first hour unless specific indication (e.g., aortic dissection)
Hypertensive emergency – infusion strategy	Start 1–2 mg/min IV infusion	Titrate every 10–20 min to BP goal; typical max cumulative ~300 mg	Useful when continuous titration is preferred; may be less flexible than nicardipine or clevidipine
Acute severe hypertension in pregnancy/postpartum	10–20 mg IV over 2 min; then 20–80 mg IV bolus	Repeat q10–30 min; max total 300 mg or start 1–2 mg/min infusion	Avoid in asthma, bradycardia, heart block, or decompensated HF
Aortic dissection (after or with beta blockade)	20 mg IV over 2 min; then 20–80 mg IV q10 min OR infusion 1–2 mg/min	Titrate quickly to HR ~60 and SBP <120 mmHg (per guideline)	Often combined with vasodilator (e.g., nicardipine) once beta blockade in place
Oral step-down after IV (general adult)	100–200 mg PO twice daily, titrated as needed	Increase every 2–3 days; usual total 200–2400 mg/day in divided doses	Use lower doses in smaller, elderly, or fragile patients; tailor to chronic BP goal
Typical maximum dosing (acute IV)	Up to 300 mg total IV (bolus + infusion) in 24 hours	Depends on response and tolerability	Beyond this, consider alternative/adjunct agents

Administration Notes: Administer IV boluses over about 2 minutes to reduce risk of abrupt hypotension or bradycardia. Because onset is within minutes and duration is a few hours, avoid stacking large doses too quickly; reassess between boluses.

Contraindications

Absolute Contraindications:

Known hypersensitivity to labetalol or other beta-blockers
Bronchial asthma or severe bronchospastic disease (risk of bronchospasm)
Second- or third-degree AV block, sick sinus syndrome, or severe bradycardia unless a functioning pacemaker is present
Cardiogenic shock or overt decompensated heart failure
Severe hypotension

Major Precautions:

Use caution in COPD or reactive airway disease; consider alternative agents if active bronchospasm is present
In pregnancy, labetalol is generally considered safe and is guideline-recommended, but IV use should be avoided in women with asthma, heart block, bradycardia, or overt heart failure
Use cautiously in patients with peripheral vascular disease, diabetes (may mask hypoglycemia), or depression
In patients with catecholamine-depleted states (e.g., prolonged shock), combined alpha/beta blockade may precipitate hypotension and reduced cardiac output
Taper oral therapy gradually when discontinuing long-term use to avoid rebound hypertension and tachycardia

Beta-2 Blockade Warning: Beta-2 blockade may lead to bronchoconstriction and can blunt beta-agonist response. Avoid in patients with significant asthma or active bronchospasm.

Adverse Effects

Common:

Hypotension, dizziness, orthostatic symptoms
Bradycardia or borderline heart block
Fatigue, weakness
Nausea, vomiting
Scalp tingling or paresthesias

Serious:

Severe hypotension and shock, especially in volume depletion or depressed LV function
Symptomatic bradycardia, high-grade AV block, or asystole
Bronchospasm in patients with asthma or reactive airways
Acute heart failure decompensation
Rare hepatotoxicity (monitor LFTs with long-term high doses)

Special Populations

Pregnancy & Lactation:

Pregnancy: Labetalol is generally considered safe and is guideline-recommended for acute severe hypertension in pregnancy (preeclampsia/eclampsia). It is a first-line IV agent alongside hydralazine and nifedipine.
Lactation: Labetalol is excreted in breast milk in small amounts; use with caution and monitor infant for signs of beta-blockade (bradycardia, hypotension, hypoglycemia)

Hepatic Impairment:

Hepatic impairment can prolong half-life and increase drug exposure
Use lower doses and titrate carefully in patients with significant liver disease
Rare hepatotoxicity has been reported with long-term high doses; monitor LFTs if prolonged use is needed

Elderly Patients:

Start with lower doses (e.g., 10–20 mg IV bolus initially)
Titrate more cautiously due to increased risk of hypotension and bradycardia
Monitor closely for orthostatic symptoms and dizziness

Renal Impairment:

No specific dose adjustment typically required for renal impairment
Monitor carefully as these patients may be more susceptible to adverse effects

Monitoring

Clinical Monitoring:

Continuous blood pressure monitoring (ECG, NIBP or arterial line) during IV boluses and infusions
Heart rate and rhythm for bradycardia, AV block, and arrhythmias
Signs of heart failure or low cardiac output (dyspnea, pulmonary edema, rising lactate)
Respiratory status in patients with any history of asthma or COPD
In pregnancy, fetal status and uterine perfusion when used for hypertensive emergencies

Laboratory Monitoring:

Liver function tests (LFTs) if prolonged or high-dose therapy is anticipated
Electrolytes and renal function as clinically indicated

Clinical Pearls

Titratable Control: IV labetalol is a good choice when you want moderate-speed BP control with relatively stable heart rate, but it is less titratable than agents like nicardipine or clevidipine for very labile pressures.

Aortic Dissection: In aortic dissection, prioritize beta blockade (labetalol or esmolol) before or alongside vasodilators to avoid reflex tachycardia and increased shear stress.

Pregnancy-Related Hypertension: For pregnancy-related severe hypertension, labetalol, hydralazine, and oral nifedipine are all guideline-supported; choose based on comorbidities (e.g., avoid labetalol in asthma).

Duration of Effect: Remember that a single large bolus may have effects lasting several hours; avoid reflexive redosing without reassessment and consider switching to a titratable infusion if frequent adjustments are needed.

Stimulant Toxicity: Mixed alpha/beta blockade makes labetalol a reasonable option in some stimulant or catecholamine excess scenarios, but data are limited and institutional practices differ.

Avoid Dose Stacking: Because onset is within minutes and duration is several hours, avoid stacking large doses too quickly. Reassess BP and heart rate between boluses.

References

1. Drugs.com. (2024). Labetalol hydrochloride injection: Monograph for professionals. https://www.drugs.com/monograph/labetalol-hydrochloride.html
2. Medscape. (2024). Trandate (labetalol) dosing, indications, interactions. https://reference.medscape.com/drug/trandate-labetalol
3. DrugBank Online. (2024). Labetalol (DB00598). https://go.drugbank.com/drugs/DB00598
4. American College of Obstetricians and Gynecologists. (2020). Gestational Hypertension and Preeclampsia (Practice Bulletin No. 222). Obstetrics & Gynecology, 135(6), e237–e260. https://doi.org/10.1097/AOG.0000000000003891
5. Farkas, J. (2024). Hypertensive emergencies. The Internet Book of Critical Care (IBCC). EMCrit Project. https://emcrit.org/ibcc/htn/