Bedside Snapshot

Use It For
Severe hypertension in pregnancy or up to 6 weeks postpartum; hypertensive emergency; BP control in acute stroke and intracerebral hemorrhage; aortic dissection (heart rate and BP)
Adult Dose
  • Pregnancy: 20 mg IV over 2 min, then 40 mg, then 80 mg every 10 min while BP ≥160/110 (max 300 mg)
  • Hypertensive emergency: 20 mg IV, then 20–80 mg every 10 min (max 300 mg)
  • Infusion: 1–2 mg/min IV
Pediatric Dose
Not FDA-established; specialist use: 0.2–1 mg/kg IV bolus (max 40 mg/dose) or 0.25–3 mg/kg/hr IV infusion
Onset / Duration
IV: within minutes, peak within 5 min / hours, dose-dependent (BP back near baseline an average 16–18 hr after an IV course); PO: peak 2–4 hr / 8–12 hr or more
Do Not Give / Hold If
Asthma or obstructive airway disease; severe bradycardia or AV block above 1st degree; overt heart failure or cardiogenic shock; IV verapamil or diltiazem. Hold if HR <60 or BP at target
Watch For
Hypotension, worse when upright (BP 5 and 10 min after each dose); bradycardia or AV block (ECG); bronchospasm (wheeze, SpO₂); hypoglycemia in fasting patients and children (glucose)
Reversal / Rescue
No specific reversal: stop, lay flat with legs up, IV fluid. Bradycardia: atropine or pacing. Shock: vasopressors (COR 1) and high-dose insulin if refractory (COR 1); glucagon 2–10 mg IV, then 1–15 mg/hr (COR 2a)
Must Remember
Boluses stack: each peaks within 5 min but lasts hours. Recheck BP at 10 min before the next dose, count the running total against 300 mg, and keep the patient supine for 3 hr

Indications

Emergency & Prehospital

  • Severe hypertension in pregnancy or up to 6 weeks postpartum: SBP ≥160 or DBP ≥110 mmHg that persists for 15 min. It is one of three first-line agents. The others are hydralazine and oral immediate-release nifedipine. Magnesium sulfate is given with it for preeclampsia with severe features, eclampsia or HELLP syndrome.
  • Hypertensive emergency: severe hypertension with acute organ injury, such as encephalopathy or acute kidney injury. The FDA label calls it severe hypertension.

ED / ICU / Transport

  • Acute ischemic stroke before and after reperfusion: bring BP below the thrombolysis and thrombectomy thresholds, and hold it there for 24 hr. Without reperfusion, permissive hypertension applies. Treat only at BP ≥220/120 mmHg, or for a comorbidity that needs it.
  • Spontaneous intracerebral hemorrhage of mild to moderate severity: lower SBP smoothly and keep it down when SBP runs 150–220 mmHg. Benefit is not established in large or severe ICH, or when surgical decompression is needed.
  • Acute aortic dissection: an IV beta-blocker controls heart rate and BP first, before any vasodilator. The alternatives are esmolol and metoprolol.
  • Hypertension with acute coronary syndrome: second-line after nitroglycerin, and only without heart failure, pulmonary edema or low output. Reperfusion comes first. Diastolic BP should stay at or above 70 mmHg.

Other Uses

  • Chronic hypertension, including in pregnancy: oral tablets. They take over once IV control is established.
  • Perioperative and postoperative hypertension: used in the PACU or ICU when beta-blockade is acceptable. It is long-acting and not finely titratable, which is why nicardipine or clevidipine suit tight titration. Avoid it with low cardiac index after coronary bypass.
  • Pediatric hypertensive emergency: specialist use (off-label)
Not first-line for pheochromocytoma or stimulant crisis: Start with alpha-blockade for pheochromocytoma. For cocaine or methamphetamine crisis, reach for benzodiazepine sedation and vasodilators first. The AHA 2025 guideline (Part 10, rec 21.6) rates sedation COR 1 (B-R), vasodilators 2a (C-LD), and beta-blockers 3: No Benefit for adults with coronary vasospasm or hypertensive emergency (C-LD). Reports describe paradoxical hypertension with labetalol in pheochromocytoma.
Suspected stroke before imaging: Hold off on lowering BP in the field unless the local stroke protocol or medical direction orders it. INTERACT4, an ambulance trial, lowered BP in suspected stroke before anyone knew the type. No overall benefit showed up. Patients who turned out to have ischemic stroke functioned worse. With no reperfusion, the approach is permissive hypertension. Consider treatment only at BP ≥220/120 mmHg, lowering about 15% in the first 24 hr.

Dosing & Administration

Doses vary by protocol; follow local protocols and medical direction.

Available Forms

  • Multiple-dose vial (common in EMS, ED and transport): 5 mg/mL in 20 mL (100 mg) or 40 mL (200 mg); contains parabens. 20 mg = 4 mL.
  • Single-dose vial and prefilled glass syringe: 5 mg/mL in 4 mL (20 mg) vial; 5 mg/mL in 2 mL (10 mg) syringe. Preservative-free.
  • Premixed bags (infusion): 1 mg/mL in 0.72% NaCl (100, 200 or 300 mL bags) or in 5% dextrose (200 mg/200 mL); ready to use.
  • Tablets: 100 mg, 200 mg and 300 mg.
High-Alert Medication: The usual errors come in three. First, pulling a dose by volume from the wrong concentration: 5 mg/mL vial vs 1 mg/mL bag is a 5-fold error. Second, losing count of the cumulative total across boluses and handoffs. Third, grabbing lamotrigine (LaMICtal) by mistake for labetalol. Before each bolus, and at every handoff, independently double-check drug, concentration, dose in mg and the running total.

Adult Dosing

IndicationDose & RouteRepeat / MaxNotes
Severe hypertension in pregnancy or ≤6 weeks postpartum (SBP ≥160 or DBP ≥110 mmHg for 15 min)
20 mg IV over 2 min; recheck in 10 min. Still severe: 40 mg IV over 2 min; recheck in 10 min. Still severe: 80 mg IV over 2 min
EMS model guideline: 80 mg every 10 min to max 300 mg cumulative, or 1–2 mg/min IV infusion. ACOG hospital algorithm: still severe after 80 mg, switch to hydralazine and call for emergent consult
High-alert Treat within 30–60 min; target SBP 130–150 and DBP 80–100 mmHg. Give with magnesium sulfate (antihypertensive first if only one can start). Asthma or bradycardia: hydralazine or nifedipine instead
Hypertensive emergency (repeated IV injection, FDA label)
20 mg IV over 2 min (0.25 mg/kg up to 20 mg), patient supine
20–80 mg IV over 2 min every 10 min until target; max 300 mg cumulative (safety above 300 mg not established)
High-alert No compelling condition: lower BP by no more than 25% in the first hour, then to about 160/100 mmHg over the next 2–6 hr, then cautiously toward normal over the following 24–48 hr
Hypertensive emergency (continuous infusion)
1–2 mg/min IV infusion (label start 2 mg/min)
Adjust to BP; stop at target and change to oral. Usual effective total 50–200 mg; max 300 mg cumulative
High-alert Steady state takes 22–28 hr, so the effect keeps building; reassess BP and heart rate often
Acute ischemic stroke, reperfusion candidate
Before reperfusion: 10–20 mg IV over 1–2 min. After reperfusion, BP above 180/105 mmHg: 10 mg IV, then 2–8 mg/min IV infusion (drug doses from the 2019 AHA/ASA BP table; the 2026 guideline sets the BP thresholds)
Bolus: may repeat once, or switch to a nicardipine or clevidipine infusion; if BP cannot be kept below 185/110 mmHg, do not give thrombolysis. Infusion: titrate to ≤180/105 mmHg; max per stroke protocol (safety above 300 mg not established)
High-alert BP below 185/110 mmHg before thrombolysis; keep at or below 180/105 mmHg during and for 24 hr after thrombolysis or thrombectomy. After successful thrombectomy reperfusion (mTICI 2b–3), a target SBP below 140 mmHg in the first 72 hr is harmful. No reperfusion: treat only at BP ≥220/120 mmHg (or for a comorbidity that needs it), lowering about 15% in the first 24 hr. The 2–8 mg/min stroke infusion is up to 4 times the label rate of 2 mg/min; at 8 mg/min the 300 mg total is reached in under 40 min, so track the running total
Spontaneous intracerebral hemorrhage, mild to moderate severity (SBP 150–220 mmHg)
10–20 mg IV over 1–2 min (usual labetalol bolus regimen; the ICH guideline sets BP targets, not drug doses)
20–80 mg every 10 min or infusion to target; max 300 mg cumulative
High-alert Start within 2 hr of onset; reach SBP 140 mmHg within 1 hr and keep 130–150 mmHg. SBP below 130 mmHg is potentially harmful. Avoid peaks and swings. Large or severe ICH, or surgical decompression: intensive lowering not established; target per neurocritical care
Acute aortic dissection
20 mg IV over 2 min, then 20–80 mg every 10 min, or 1–2 mg/min IV infusion (label regimen applied to dissection)
Heart rate 60–80 bpm and SBP below 120 mmHg (or the lowest BP that keeps organs perfused); max 300 mg cumulative
High-alert Rate control first; add nicardipine or clevidipine only if BP stays high. Arterial line; analgesia
Oral step-down after IV control
200 mg PO once supine diastolic BP starts to rise, then 200 or 400 mg PO 6–12 hr later
Titrate daily in hospital from 200 mg to 1,200 mg twice daily; max 2,400 mg/day
Pregnancy: 200 mg PO every 12 hr, up to 800 mg every 8–12 hr (max 2,400 mg/day)

Pediatric Dosing

Not established in children: FDA has not established safety or effectiveness here. The AAP 2017 pediatric guideline lists labetalol for acute severe hypertension with life-threatening symptoms, for specialists only. Over the first 8 hr, cut BP by no more than 25% of the planned reduction.
IndicationDose (per kg) & RouteMax Single / Max TotalNotes
Acute severe hypertension, bolus (specialist use)
0.2–1 mg/kg IV bolus
Max 40 mg/dose; repeat interval per pediatric critical care or medical control
High-alert Asthma and overt heart failure are relative contraindications. Watch for hypoglycemia
Acute severe hypertension, infusion (specialist use)
0.25–3 mg/kg/hr IV infusion (weight-based)
Max 3 mg/kg/hr
High-alert PICU or pediatric transport team; pump with pediatric library
Neonates
Not established in children: specialist use only
—
Neonatal intensivist dosing only. Newborns exposed in utero: watch for bradycardia, hypotension, hypoglycemia and respiratory depression

Run the weight-based dosing check, and set BP targets by age (see Pediatric Vital Signs).

Continuous Infusion

SettingExample ConcentrationStartTitrateUsual Range / Max
Adult, premixed bag
1 mg/mL (100, 200 or 300 mL bag), example (institution-specific)
2 mg/min (2 mL/min)
Adjust to BP response; stop when target reached
1–2 mg/min; max 300 mg cumulative
Adult, compounded (label method)
200 mg (40 mL of 5 mg/mL) added to 160 mL = 1 mg/mL, example (institution-specific)
2 mg/min (2 mL/min)
Adjust to BP response; stop when target reached
1–2 mg/min; max 300 mg cumulative

Preparation & Administration

  • Dilution: none for an IV push. Give the 5 mg/mL undiluted. Premixed bags need no dilution. Add nothing to the bag, and discard it 24 hr after the infusion starts.
  • Push rate: over 2 min, with the patient supine. Measure BP just before, then 5 and 10 min after each injection. The peak effect comes within 5 min.
  • Flush: 0.9% NaCl after each bolus. Never share the line with sodium bicarbonate, which is incompatible, or with alkaline drugs such as furosemide, which form a white precipitate.
  • Line: peripheral IV for boluses and infusions. The label has no extravasation warning.
  • Prefilled glass syringe: may break, clog or disconnect on some needleless connectors. Keep the collar on, and check the connection during the push.
  • Pump requirement: run infusions on a smart pump, in mg/min for adults or mg/kg/hr for children.
  • Positioning: keep the patient supine during dosing and for 3 hr after. Check how they tolerate sitting before any walking.

Contraindications & Precautions

Contraindications

  • Bronchial asthma or obstructive airway disease.
  • Severe sinus bradycardia, or heart block greater than first degree without a functioning pacemaker.
  • Overt heart failure or cardiogenic shock.
  • Other states of severe, prolonged hypotension.
  • IV administration of a non-dihydropyridine calcium channel blocker (verapamil, diltiazem).
  • Hypersensitivity, including anaphylaxis, to labetalol or a product component.

Precautions

  • Pheochromocytoma and stimulant toxicity: see the warning in Indications.
  • COPD or nonallergic bronchospasm: not studied at IV doses. Avoid.
  • Compensated heart failure: use caution. Low cardiac index after coronary bypass: avoid.
  • Diabetes, fasting, vomiting, children: it masks the tachycardia that would warn you, and it raises the risk of severe hypoglycemia.
  • Anaphylaxis risk: avoid it in patients at high risk of anaphylaxis. Reactions may resist usual epinephrine doses.
  • Coronary artery disease on chronic therapy: do not stop it abruptly.
  • Liver disease: rare severe hepatocellular injury can occur. It may progress slowly with few symptoms. Run periodic liver tests during ongoing therapy. Stop permanently for jaundice or laboratory evidence of liver injury.
  • Cataract surgery: alpha-1 blockade can cause intraoperative floppy iris syndrome. Tell the ophthalmologist.

Hold / Reassess If

  • BP at or below target (pregnancy: SBP 130–150 and DBP 80–100 mmHg): stop dosing; recheck per algorithm.
  • Heart rate below 60 bpm (common protocol threshold), new AV block above first degree or a pause: hold; see Reversal.
  • Wheeze, falling SpO₂, crackles or new hypotension: stop the infusion and reassess.
  • Cumulative dose approaching 300 mg without control: change agent and get expert input.

Adverse Effects & Toxicity

Common

  • Symptomatic postural hypotension: 58% if tilted or upright within 3 hr of an IV dose
  • Nausea (13%) and vomiting (4%)
  • Dizziness (9%)
  • Tingling of the scalp or skin (7%)
  • Sweating (4%), flushing
  • Transient rise in BUN and creatinine (8%), mainly with a BP drop in prior renal insufficiency

Serious / Life-Threatening

EffectRecognitionManagement
Hypotension
BP below target, dizziness, syncope on sitting; in pregnancy, fetal heart rate decelerations
Stop dosing, lay flat with legs raised (left lateral tilt in pregnancy), IV fluid; vasopressor if needed
Bradycardia, AV block, sinus pause, arrest
Heart rate trend and rhythm on continuous ECG
Hold; atropine, pacing, then glucagon or high-dose insulin if refractory; ACLS
Bronchospasm
Wheeze, rising work of breathing, falling SpO₂
Stop; inhaled beta-agonist (response may be blunted); epinephrine if severe
Acute heart failure
Crackles, hypoxia, falling output
Stop; diuretic and ventilatory support; inotrope if low output
Hypoglycemia
Low glucose without tachycardia; confusion, sweating
Check glucose; dextrose; more frequent checks in fasting patients and children
Hepatocellular injury (rare)
Jaundice, dark urine, right upper quadrant pain, raised transaminases
Stop and do not restart without another explanation

Overdose & Toxicity Management

  • Signs: hypotension that depends on posture, and bradycardia. In large ingestions, expect heart failure, bronchospasm and seizures.
  • Immediate: lay the patient flat with legs raised. Start IV fluids and continuous ECG. Involve poison control early.
  • Bradycardia: give atropine (the label also lists epinephrine), and pace if there is no response. These are standard ALS steps, not a Part 10 beta-blocker recommendation. Glucagon is COR 2a (C-LD) for symptomatic bradycardia or hypotension (see Antidote).
  • Hypotension or shock: Expect more hypotension than with a pure beta-blocker. The alpha-1 blockade adds vasodilation. Start vasopressors early (AHA 2025 Part 10 21.4, COR 1, C-EO; the label suggests norepinephrine). For hypotension refractory to vasopressors, use high-dose insulin (COR 1, C-LD), with a dextrose infusion and frequent glucose and potassium checks. VA-ECMO comes in for cardiogenic shock refractory to drug therapy (COR 2a, C-LD adults). Involve toxicology.
  • Antidote: glucagon. Adults get 2–10 mg IV bolus, then 1–15 mg/hr infusion (AHA 2025 Part 10 Table 4; rec 21.4 COR 2a, C-LD). Use it after vasopressors and high-dose insulin. Children: 0.05–0.15 mg/kg bolus, not above the adult dose. The infusion is per poison center, because there is no guideline value. This differs from the FDA label. The labetalol label regimen (5–10 mg IV over 30 sec, then 5 mg/hr) sits inside the AHA range of 2–10 mg then 1–15 mg/hr. Expect vomiting, and protect the airway.
  • Extracorporeal removal: not useful. Hemodialysis and peritoneal dialysis remove less than 1%.

Monitoring
ParameterWhen / How OftenTarget / Act If
Clinical: blood pressure
Before each bolus and 5 and 10 min after; at least every 15 min in EMS; arterial line for dissection or infusion titration
At target: stop dosing. Below target or symptomatic: lay flat, fluid. Pregnancy: SBP 130–150 and DBP 80–100 mmHg
Clinical: BP after pregnancy target reached
Every 10 min for 1 hr, every 15 min for 1 hr, every 30 min for 1 hr, then hourly for 4 hr
Back to SBP ≥160 or DBP ≥110 mmHg: repeat the drug and dose that worked
Clinical: heart rate and rhythm
Continuous ECG
Below 60 bpm (protocol threshold), AV block above first degree or pause: hold; atropine or pacing (see Conduction Blocks)
Clinical: respiratory
Lung sounds and SpO₂ with each reassessment
Wheeze or crackles: stop; treat bronchospasm or heart failure
Clinical: neurologic and fetal
Stroke and ICH: neuro checks with each BP. Pregnancy: fetal heart rate when available
New deficit or fetal decelerations during BP lowering: reassess the target and call for help
Laboratory: glucose
Baseline in diabetes, fasting, vomiting or children; newborns after in-utero exposure
Low: give dextrose; increase checks
Laboratory: liver panel
At the first sign or symptom of liver dysfunction (pruritus, dark urine, persistent anorexia, jaundice, right upper quadrant tenderness, unexplained flu-like symptoms); periodically during ongoing oral therapy
Jaundice or raised transaminases: stop labetalol permanently
Laboratory: creatinine
Baseline and daily in kidney disease
Rise after a BP drop: reassess the BP target and volume
Infusion safety: cumulative dose
After every bolus, each hour on infusion and at handoff
Approaching 300 mg without control: change agent and get expert input

Interactions & Compatibility

Clinically Significant Interactions

Drug / ClassEffectWhat To Do
Calcium-channel blockers (IV verapamil or diltiazem)
Additive AV block, bradycardia and hypotension
Contraindicated with IV non-dihydropyridine CCBs (verapamil, diltiazem). The current label advises avoiding labetalol with calcium-channel antagonists in general. Adding nicardipine or clevidipine after beta-blockade is guideline practice (aortic dissection), not a label allowance; monitor BP and heart rate closely
Other antihypertensives and nitroglycerin
Additive hypotension; labetalol blunts the reflex tachycardia of nitrates
Smaller increments, closer BP checks
Beta-agonist bronchodilators (albuterol)
Bronchodilator effect antagonized
Avoid labetalol in asthma; larger beta-agonist doses may be needed
Epinephrine for anaphylaxis
Usual doses may not work in beta-blocked patients
Anticipate a poor response and escalate per anaphylaxis protocol
Halothane (label) and other volatile anesthetics
Halothane 3% or more: synergistic hypotension and fall in cardiac output (labeled). Current volatile agents: additive hypotension expected, not a labeled interaction
Tell the anesthesia team; avoid high concentrations
Insulin and other antidiabetics
Hypoglycemia masked or prolonged; insulin release blunted
Monitor glucose; adjust antidiabetic doses
Cimetidine; tricyclic antidepressants (oral labetalol)
Cimetidine raises oral labetalol bioavailability; more tremor reported with tricyclics (2.3% vs 0.7%)
Titrate oral doses carefully; watch for tremor
Urine catecholamine and drug screens
Falsely high urine catecholamines and metanephrines; false-positive amphetamine immunoassay
Use specific assays (HPLC, GC-MS) to confirm

IV Compatibility

  • Compatible diluents (24 hr, room temperature or refrigerated): at 1.25–3.75 mg/mL: 0.9% NaCl, D5W, lactated Ringer's, Ringer's, D5/Ringer's, D5/lactated Ringer's, D5/0.2% NaCl, D5/0.33% NaCl, D5/0.9% NaCl and D2.5/0.45% NaCl (the fluids the label tested).
  • Incompatible: 5% sodium bicarbonate. Alkaline drugs such as furosemide form a white precipitate in the line, so use separate lines.
  • Premixed bags: add no other drugs to the bag.
  • Verify with an institutional compatibility resource.

Special Populations
  • Pediatrics: not FDA-established. Specialist use only, for acute severe hypertension (see the Pediatric Dosing table). Hypoglycemia risk is higher. Asthma and overt heart failure are relative contraindications.
  • Neonates: no established dosing. Newborns whose mothers received labetalol may show bradycardia, hypotension, hypoglycemia or respiratory depression. Monitor them after delivery.
  • Pregnancy: extensive published experience has not found a drug-associated risk of major birth defects, miscarriage or adverse maternal or fetal outcomes. Labetalol crosses the placenta. Why treat fast? Untreated severe hypertension carries a risk of maternal stroke. That is why you treat within 30–60 min. IV labetalol is a first-line agent.
  • Lactation: it shows up in milk at low levels, about 0.004% of the maternal dose. There are no data on effects in the breastfed infant or on milk production. Weigh the benefits of breastfeeding against the mother's need for labetalol.
  • Older Adults: elimination is reduced. Start at usual doses, but expect lower maintenance needs. Guard against orthostatic falls.
  • Renal Impairment: no specific adjustment is established, and the half-life does not change. BUN and creatinine may rise briefly as BP falls. Neither hemodialysis nor peritoneal dialysis removes it.
  • Hepatic Impairment: the IV half-life does not change. Oral bioavailability rises, though, because first-pass metabolism falls. Use lower oral doses and titrate slowly. Stop for jaundice or liver injury.
  • Obesity / Dosing Weight: the label's first dose is 0.25 mg/kg up to 20 mg. For adults of 80 kg or more, that is 20 mg. Later boluses and infusions are fixed in mg. No obesity-specific adjustment is established. Pediatric doses use actual weight, with a 40 mg/dose cap.

Field & Transport Considerations
  • Scope: advanced EMS clinicians (AEMT, Paramedic) where it is carried, and RN and critical-care transport, per local protocol. The scope varies by state and agency protocol. The 2025 NAEMSP/ACOG model guideline places it in the advanced-clinician tier for severe hypertension in pregnancy.
  • Storage & Stability: store at 20–25°C (68–77°F), with excursions to 15–30°C (59–86°F). Protect it from light, do not freeze it, and keep it in the carton. Bags stay in the overwrap until use.
  • Carried Concentration: vials are 5 mg/mL (20 mg = 4 mL). Bags are 1 mg/mL. Label the syringe in mg. Never draw a bolus from a bag by the same mL you would use for a vial.
  • Severe Hypertension in Pregnancy: confirm SBP ≥160 or DBP ≥110 mmHg after 15 min, then treat within 30–60 min. Request a paramedic intercept if you need one. Recheck BP at least every 15 min. Transport to a hospital with obstetric services. There is no evidence for nitroglycerin in pregnancy-related hypertension.
  • Suspected Stroke: do not lower BP before imaging unless the local stroke protocol or medical direction orders it (see the warning in Indications). After thrombolysis or thrombectomy, on an interfacility transfer, keep BP at or below 180/105 mmHg per the sending protocol.
  • Infusions in Transport: run the smart pump on its own line. Confirm the bag concentration matches the pump library. Carry enough volume for the trip.
  • Positioning: supine, with left lateral tilt in pregnancy. Avoid sudden sitting up during moves.
  • Handoff Essentials: each dose with time, cumulative mg, BP and heart rate response, current infusion rate, magnesium given, seizure activity and fetal status if known.

Clinical Pearls
Pheochromocytoma trap: Labetalol is mostly a beta-blocker, about 7 parts beta to 1 part alpha IV. In a catecholamine-secreting tumor, paradoxical hypertension has been reported. Establish alpha-blockade first. Never rely on beta-blockade alone.
The 3-hour supine rule: More than half of patients get symptomatic postural hypotension if they sit or stand within 3 hr of IV labetalol. Keep the stretcher flat. Supervise the first time the patient stands.
Ten minutes, not twenty: Labetalol peaks within about 5 min. That is why the pregnancy algorithm rechecks BP at 10 min. Hydralazine and oral nifedipine need 20 min. Give the slower drugs a second dose too soon and BP overshoots.
Labetalol vs other IV antihypertensives:
  • Labetalol: boluses or infusion. It slows heart rate. Long-acting, and not finely titratable.
  • Nicardipine or clevidipine: titratable dihydropyridine infusions. They may cause reflex tachycardia.
  • Esmolol: beta-1 selective infusion. Its effect fades within minutes of stopping.
  • Hydralazine: slower boluses, so recheck at 20 min. Useful in asthma or bradycardia.
Exam discriminator: Preeclampsia with severe-range BP in a patient with asthma: choose hydralazine or nifedipine, not labetalol. Aortic dissection: bring heart rate to 60–80 bpm with a beta-blocker first, then add a vasodilator. A vasodilator alone causes reflex tachycardia and more shear stress.
Lab confounders: Labetalol metabolites push urine catecholamine and metanephrine results up on older assays. They can also cause a false-positive amphetamine immunoassay. Mention labetalol when you send a pheochromocytoma work-up or drug screen.

Pharmacology

Mechanism of Action

  • Nonselective beta-blockade (beta-1 and beta-2) → slower heart rate and less reflex tachycardia → BP falls, and the heart does not race to keep up.
  • Selective alpha-1 blockade → arteriolar and venous dilation → lower systemic vascular resistance. BP falls more when standing than when supine.
  • Ratio: alpha to beta blockade runs about 1:7 after IV and 1:3 after oral dosing. Beta effects dominate.
  • Beta-2 blockade → bronchoconstriction in reactive airways, and a blunted response to beta-agonists.

Pharmacokinetics

RouteOnsetPeakDuration
IV bolus or infusion
Within minutes
Within 5 min of each injection
Dose-dependent; after IV courses BP drifted back to baseline over an average 16–18 hr
PO
Within 1–3 hr (plasma peak 1–2 hr)
2–4 hr
At least 8 hr (100 mg) to over 12 hr (300 mg)
  • Half-life: about 5.5 hr IV; 6–8 hr oral. Infusion steady state takes 22–28 hr.
  • Metabolism: hepatic glucuronide conjugation; extensive first-pass (oral bioavailability about 25%, higher with food).
  • Active metabolites: none.
  • Elimination: 55–60% in urine as conjugates or unchanged drug within 24 hr; the rest in bile and feces. Not dialyzable.
  • Protein binding / Vd: about 50% bound; crosses the placenta; negligible blood–brain barrier passage in animals.

Names & Classification
Generic Name
Labetalol hydrochloride
Brand Names
Trandate (US, discontinued); Normodyne (US, discontinued); US injection and tablets are now generic
Pharmacologic Class
Nonselective beta-adrenergic and selective alpha-1-adrenergic blocker
Therapeutic Class
Antihypertensive
Controlled Substance
Not controlled
ISMP High-Alert
Yes: ISMP high-alert medication (adrenergic antagonists, IV), 2024 acute care list
Look-Alike / Sound-Alike
labetalol / LaMICtal; labetalol / lamoTRIgine; Normodyne / Norpramin (ISMP List of Confused Drug Names, 2024)

Related

References
  1. Hospira, Inc. (2022). Labetalol hydrochloride injection, USP, 5 mg/mL multiple-dose vials: prescribing information (revised 11/2022); and Hikma Pharmaceuticals USA. (2024). Labetalol HCl in sodium chloride, labetalol HCl in dextrose and labetalol hydrochloride injection, for intravenous use: prescribing information (revised 8/2024). DailyMed, U.S. National Library of Medicine, accessed October 2026. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=abfc6b75-1ed5-41f1-0484-4597488237bc; https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=99a715a0-4579-410c-b102-7ef6fab8db55
  2. National Association of EMS Physicians and American College of Obstetricians and Gynecologists. (2025). Elevated blood pressure in pregnancy and up to 6 weeks postpartum: model EMS guideline. NAEMSP; and American College of Obstetricians and Gynecologists. (2020). Gestational hypertension and preeclampsia. ACOG Practice Bulletin No. 222. Obstetrics & Gynecology, 135(6), e237–e260; and ACOG. (2023). Acute hypertension in pregnancy and postpartum algorithm. ACOG Obstetric Emergencies program. https://naemsp.org/wp-content/uploads/2025/04/Elevated-BP-Model-EMS-Guideline_with-logos_Secured-1.pdf; https://doi.org/10.1097/AOG.0000000000003891; https://www.acog.org/-/media/project/acog/acogorg/files/pdfs/programs/ob-emergencies/hypertension_algorithm.pdf
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