Metoprolol
Indications
Metoprolol is one of the most widely prescribed β1-selective beta-blockers, available as two distinct salt forms with different release profiles, dosing schedules, and approved indications. Choosing between metoprolol tartrate (immediate-release) and metoprolol succinate (extended-release) is a clinically meaningful decision: only succinate is FDA-approved for chronic heart failure, while tartrate carries the IV formulation used in acute myocardial infarction. The two salts can be substituted at the same total daily dose for hypertension and angina, but they are not interchangeable for the heart-failure indication.
| Indication | Salt Form / Population | Therapy Type | Status |
|---|---|---|---|
| Hypertension — to lower blood pressure and reduce the risk of fatal and non-fatal cardiovascular events | Tartrate (adults); Succinate (adults; paediatric ≥6 years) | Monotherapy or combination with other antihypertensives (e.g., thiazides) | FDA Approved |
| Angina pectoris — long-term management of chronic stable angina | Tartrate and succinate (adults) | Monotherapy or with nitrates / calcium channel blockers | FDA Approved |
| Acute myocardial infarction — to reduce cardiovascular mortality in haemodynamically stable patients | Tartrate (oral) — alone or in conjunction with intravenous metoprolol | IV initiation in selected patients followed by oral therapy | FDA Approved |
| Heart failure — to reduce the risk of cardiovascular mortality and heart-failure hospitalisation | Succinate only — adults with stable heart failure; MERIT-HF enrolled NYHA II–IV with LVEF ≤40% on standard background therapy (ACEi/ARB, diuretics, ± digoxin) | Adjunct to standard heart failure therapy | FDA Approved (succinate) |
| Atrial fibrillation / flutter — rate control | Tartrate (oral and IV) and succinate | Monotherapy or with digoxin / non-dihydropyridine CCB | Off-Label (guideline-supported first-line) |
| Migraine prophylaxis | Tartrate or succinate (adults) | Adjunct to lifestyle modification and trigger avoidance | Off-Label (AAN Level A) |
| Supraventricular tachyarrhythmias — acute and chronic suppression | Tartrate (oral and IV) | Often after adenosine or non-dihydropyridine CCB | Off-Label |
| Performance / situational anxiety, essential tremor | Tartrate (low dose, intermittent) | Symptom-targeted use | Off-Label (limited evidence) |
The acute MI mortality reduction labelled in the Lopressor prescribing information is supported by a 1,395-patient placebo-controlled randomised trial (the Göteborg Metoprolol Trial, Hjalmarson 1981) that demonstrated a 36% reduction in 3-month mortality. The MIAMI trial (5,778 patients) was a separate study that showed a numerically smaller, statistically non-significant reduction in 15-day mortality. The heart failure indication for metoprolol succinate is supported by MERIT-HF (3,991 patients with NYHA II–IV heart failure and LVEF ≤0.40), which was stopped early after a statistically significant reduction in all-cause mortality (relative risk reduction ~34%). The mortality benefit is salt-form specific: metoprolol tartrate has not demonstrated a comparable mortality reduction in chronic heart failure and is not FDA-labelled for this indication.
Atrial fibrillation rate control — IV metoprolol tartrate is widely used in acute settings; oral metoprolol is recommended for chronic rate control by the 2023 ACC/AHA/ACCP/HRS atrial fibrillation guideline. Evidence quality: high.
Migraine prophylaxis — supported by the 2012 American Academy of Neurology guideline as a Level A option (established as effective). Evidence quality: high.
Performance anxiety, essential tremor — propranolol is more conventionally used; metoprolol is an alternative when β1-selectivity is preferred. Evidence quality: low.
Hyperthyroidism (symptomatic management) — used to control adrenergic symptoms while definitive therapy takes effect. Withdraw cautiously to avoid precipitating thyroid storm. Evidence quality: moderate.
Dosing
| Clinical Scenario | Starting Dose | Titration / Maintenance | Maximum Dose | Notes |
|---|---|---|---|---|
| Hypertension — adult, tartrate (IR) | 100 mg PO daily in single or 2 divided doses, with or after food | Adjust at weekly or longer intervals; effective range 100–450 mg/day | 450 mg/day | Maximum effect of any given dose apparent after about 1 week Lower once-daily doses (especially 100 mg) may not maintain a full effect at the end of 24 hours — divided dosing then preferred |
| Hypertension — adult, succinate (ER) | 25–100 mg PO once daily | Titrate at weekly or longer intervals; effective range 100–400 mg/day | 400 mg/day | Once-daily dosing supports adherence; maximum effect of any given dose apparent after about 1 week |
| Hypertension — paediatric ≥6 years, succinate (ER) | 1 mg/kg PO once daily (not to exceed 50 mg) | Titrate based on response | 2 mg/kg/day or 200 mg/day (whichever is lower) | Tablets should be swallowed whole; can be divided along the scoreline but not crushed or chewed |
| Chronic stable angina — adult, tartrate (IR) | 100 mg PO daily in two divided doses | Increase weekly to symptom control or pronounced HR slowing; range 100–400 mg/day | 400 mg/day | Discontinue gradually over 1–2 weeks if stopping |
| Chronic stable angina — adult, succinate (ER) | 100 mg PO once daily | Titrate weekly to clinical response; range up to 400 mg/day | 400 mg/day | Same total daily dose may be substituted from tartrate to succinate |
| Acute MI — IV early treatment, tartrate | 5 mg IV slow push every 2 minutes × 3 doses (15 mg total) as tolerated | Followed by oral therapy (see below) | 15 mg IV cumulative | Per the IV labelling, withhold for HR <45 bpm, SBP <100 mmHg, 2nd/3rd-degree AV block, PR ≥0.24 s, or decompensated heart failure Continuous ECG and BP monitoring during administration |
| Acute MI — oral, tartrate (after IV) | Patients tolerating full IV dose: 50 mg PO every 6 hours × 48 hours, starting 15 minutes after the last IV dose | Then titrate to maintenance 100 mg PO BID | 100 mg PO BID | If patient intolerant of full IV dose, start oral at 25 mg every 6 hours × 48 hours Continue therapy for at least 3 months; longer continuation reasonable per evidence with other beta-blockers |
| Heart failure — succinate ER (adults, stable) | Less severe HF: 25 mg PO once daily × 2 weeks More severe HF: 12.5 mg PO once daily × 2 weeks | Double the dose every 2 weeks as tolerated to highest tolerated or target dose | 200 mg/day | Patient must be clinically stable on background ACEi/ARB and diuretic before initiation. Reduce dose or temporarily hold for symptoms of decompensation; do not stop abruptly Tartrate is NOT FDA-approved for chronic HF and lacks comparable mortality data |
| Atrial fibrillation — acute IV rate control, tartrate | 2.5–5 mg IV slow push over 2 minutes; may repeat every 5 minutes up to 15 mg total | Transition to oral once rate is controlled | 15 mg IV cumulative (typical) | Continuous ECG and BP monitoring; avoid in pre-excitation (e.g., WPW with AF) |
| Discontinuation | Reduce gradually over 1–2 weeks (typical halving every 3–7 days) | Abrupt withdrawal may exacerbate ischaemia, precipitate MI in CAD, or cause rebound tachycardia/hypertension | ||
Population-Specific Considerations
| Population | Adjustment | Rationale |
|---|---|---|
| Renal impairment (any eGFR, including dialysis) | No adjustment | Less than 5–10% of an oral dose is excreted unchanged in urine; renal failure does not alter systemic exposure or half-life clinically meaningfully. Haemodialysis is unlikely to make a useful contribution to elimination |
| Hepatic impairment | Initiate at lower doses; titrate gradually | Extensive first-pass hepatic metabolism — plasma levels rise substantially with poor hepatic function. Formal severity-graded recommendations are not provided in the FDA labels |
| Elderly | Consider lower starting dose | FDA label notes greater frequency of decreased hepatic, renal, or cardiac function and concomitant disease in older patients; slightly higher plasma concentrations are observed but not generally clinically significant |
| Paediatric <6 years | Not established | Safety and efficacy not established |
| CYP2D6 poor metabolisers | No specific dose adjustment, but expect higher exposure and longer half-life | Approximately 8% of patients of European ancestry and ~2% of most other populations are poor metabolisers per the FDA label; plasma metoprolol exposure is several-fold higher and half-life extends to 7–9 hours |
| Pregnancy | Use only if benefit clearly outweighs risk | Crosses placenta; may cause fetal/neonatal hypotension, hypoglycaemia, bradycardia, and respiratory depression. Often used despite this when treatment is necessary (e.g., pregnancy-associated hypertension); monitor neonate at and after delivery |
The salt forms can be substituted on a milligram-for-milligram daily-dose basis for hypertension and angina (e.g., metoprolol tartrate 50 mg BID → metoprolol succinate 100 mg once daily), although peak-to-trough variability is greater with the immediate-release form. For heart failure, only succinate carries the FDA mortality indication; tartrate has not demonstrated comparable benefit. The choice between the two is also driven by adherence: succinate is preferred for chronic outpatient use because once-daily dosing supports adherence; tartrate is preferred when rapid titration is needed (e.g., post-MI, AF rate control, hospitalised patients) and is the only oral formulation that mirrors the IV preparation for transition.
Pharmacology
Mechanism of Action
Metoprolol is a competitive antagonist at β1-adrenergic receptors. At therapeutic doses it preferentially blocks cardiac β1 receptors, with relatively less effect on β2 receptors in bronchial and vascular smooth muscle — though this cardioselectivity is concentration-dependent and is lost at higher plasma concentrations (above approximately 300 nmol/L per the FDA label). Metoprolol does not have intrinsic sympathomimetic activity, and membrane-stabilising activity is detectable only at plasma concentrations far above those required for beta-blockade.
Acute β1 blockade reduces resting and exercise heart rate, slows AV nodal conduction, and decreases myocardial contractility — effects that translate to lower cardiac output, reduced myocardial oxygen demand, and lowered blood pressure. Chronic blockade is also associated with renin suppression and resetting of central sympathetic tone. In heart failure, the long-term benefit derives from reverse remodelling, reduced sympathetic drive, and protection from arrhythmic death — effects that are paradoxically opposite to the acute negative inotropic effect, which is why heart failure dosing must start low and titrate slowly.
ADME Profile
| Parameter | Value | Clinical Implication |
|---|---|---|
| Absorption | Rapid and nearly complete oral absorption; absolute bioavailability ~50% (tartrate IR) due to extensive saturable presystemic metabolism. Succinate ER bioavailability is ~77% relative to the same daily dose of tartrate, with lower peak and longer time to peak. Significant beta-blocking effect occurs within 1 hour of oral administration | Tartrate provides faster onset; succinate provides flatter peak-to-trough profile and stable 24-hour β1 blockade with once-daily dosing |
| Distribution | Extensively distributed; volume of distribution 3.2–5.6 L/kg. Approximately 10–12% bound to serum albumin. Lipophilic — crosses the blood-brain barrier with appreciable CSF concentrations; also crosses placenta and is found in breast milk. Not a significant P-glycoprotein substrate | CNS penetration accounts for fatigue, vivid dreams, sleep disturbance, and depressive symptoms more than with hydrophilic agents (atenolol, nadolol) |
| Metabolism | Hepatic, predominantly via CYP2D6 (stereoselective). CYP2D6 is absent in ~8% of patients of European ancestry (poor metabolisers) and ~2% of most other populations. Quinidine (a strong CYP2D6 inhibitor) doubled metoprolol concentrations and tripled S-metoprolol; propafenone increased steady-state metoprolol concentration 2- to 5-fold | Strong CYP2D6 inhibitors (paroxetine, fluoxetine, quinidine, propafenone, bupropion) materially raise metoprolol exposure and may exaggerate bradycardia, hypotension, and CNS effects. Cardioselectivity decreases at higher plasma concentrations |
| Elimination | Mean elimination half-life 3–4 hours (extensive metabolisers); 7–9 hours (poor metabolisers). About 95% of an oral dose is recovered in urine, but less than 5% of an oral dose (and <10% of an IV dose) is excreted as unchanged drug — most as inactive metabolites. Up to 30–40% may be excreted unchanged in poor metabolisers | No renal dose adjustment required and not removed by haemodialysis. Hepatic impairment substantially raises exposure — initiate at low dose |
Metoprolol’s β1 selectivity is preserved at therapeutic plasma concentrations but progressively diminishes above ~300 nmol/L, with meaningful β2 antagonism at total daily doses approaching the upper limits or in CYP2D6 poor metabolisers. This is clinically relevant for patients with reactive airways disease — even those who tolerate low-dose metoprolol may unmask bronchospasm with up-titration, with addition of a strong CYP2D6 inhibitor, or if they are previously unrecognised poor metabolisers. Bronchodilators should be readily available, and the lowest effective dose should be used.
Side Effects
The metoprolol adverse-effect profile reflects β1 (cardiac) antagonism, partial β2 antagonism at higher concentrations, and CNS penetration. The figures below are drawn directly from the FDA prescribing information for Lopressor (metoprolol tartrate, revised July 2023) and Toprol-XL (metoprolol succinate). The Lopressor PI separates adverse-event rates by clinical setting — most adverse effects in hypertension and angina are mild and transient, while rates in the acute MI population are markedly higher, reflecting the acute haemodynamic context.
| Adverse Effect | Reported Incidence | Clinical Note |
|---|---|---|
| Tiredness | ~10% | Often improves over the first 2–4 weeks; consider lowering dose before stopping. |
| Dizziness | ~10% | Usually orthostatic; counsel patients to rise slowly. More common at initiation and after dose increases. |
| Depression | ~5% | CNS-penetrant beta-blockers carry a small but real association with depressive symptoms; consider switching to a less lipophilic agent (atenolol, nadolol, bisoprolol) if clinically meaningful. |
| Diarrhoea | ~5% | Usually mild; rarely dose-limiting. |
| Pruritus or rash | ~5% | Usually mild; consider another beta-blocker if persistent. Photosensitivity and worsening of psoriasis have also been reported. |
| Shortness of breath, bradycardia | ~3% each | If symptomatic bradycardia (HR <50 bpm with light-headedness or fatigue), reduce dose or hold. Dyspnoea may signal worsening HF, bronchospasm, or underlying disease. |
| Cold extremities, palpitations, peripheral oedema, hypotension, heart failure exacerbation, wheezing/dyspnoea | ~1% each | Cold extremities and arterial-insufficiency-type symptoms reflect loss of β2-mediated vasodilatation. Wheezing requires reassessment of bronchospasm risk. |
| Mental confusion, short-term memory loss, headache, nightmares, insomnia | Reported (frequency not specified) | Lipophilic CNS penetration. Consider dosing earlier in the day or switching to a less lipophilic agent. |
| Sexual dysfunction (erectile dysfunction, decreased libido) | Class effect (PI references published literature) | Often underreported by patients. A vasodilating beta-blocker (nebivolol) may have a more favourable sexual side-effect profile if this is a barrier to adherence. |
| Adverse Effect | Lopressor vs Placebo | Clinical Note |
|---|---|---|
| Hypotension (SBP <90 mmHg) | 27.4% vs 23.2% | Reflects the acute haemodynamic context. Hold doses for SBP <100 mmHg per IV labelling. |
| Bradycardia (HR <40 bpm) | 15.9% vs 6.7% | Hold doses for HR <45 bpm per IV labelling. |
| First-degree heart block (PR ≥0.26 s) | 5.3% vs 1.9% | Hold doses for PR ≥0.24 s per IV labelling. |
| Second- or third-degree heart block | 4.7% vs 4.7% | No excess versus placebo, but is a contraindication when present at baseline. |
| Heart failure | 27.5% vs 29.6% | No excess versus placebo, despite the negative inotropic effect — consistent with the overall mortality benefit observed. |
| Adverse Effect | Estimated Frequency | Typical Onset | Required Action |
|---|---|---|---|
| Symptomatic bradycardia, sinus pause, intensified AV block, cardiac arrest | Rare; risk higher with concomitant non-DHP CCB or pre-existing conduction disease | Hours to days after initiation or dose increase | Hold drug; atropine; transcutaneous or transvenous pacing for high-grade AV block; IV glucagon (3–10 mg) for refractory beta-blocker toxicity |
| Worsening heart failure during titration | Reported during HF up-titration in clinical trials | Days to weeks after dose increase | Increase diuretic; restore clinical stability; reduce or temporarily hold metoprolol; resume once stable. Episodes do not preclude subsequent successful titration |
| Bronchospasm (wheezing, dyspnoea) | ~1% in HTN/angina trials; risk rises with higher doses | Within hours of dose | Inhaled β2-agonist; discontinue metoprolol if recurrent or severe |
| Severe rebound on abrupt withdrawal (ischaemia, MI, ventricular arrhythmia) | Documented in ischaemic heart disease patients | Days after stopping | Avoid abrupt withdrawal; taper over 1–2 weeks; reinstitute promptly if rebound occurs |
| Anaphylaxis with relative resistance to adrenaline | Rare | Variable | Higher-dose adrenaline, IV glucagon, IV fluids, antihistamines, corticosteroids |
| Severe / prolonged hypoglycaemia (especially in fasting / surgical patients or children) | PI-specified risk | During hypoglycaemic episodes | Counsel on non-adrenergic warning signs (sweating preserved); seek emergency treatment for severe hypoglycaemia; review SMBG frequency in insulin-treated patients |
| Thyroid storm precipitated by abrupt withdrawal | Rare | Days after stopping | In patients with thyrotoxicosis, withdraw beta-blocker only after definitive thyroid therapy is established and gradually |
| Hypertensive crisis in unrecognised pheochromocytoma (without alpha-blockade) | Rare but predictable | Within hours | Always start alpha-blocker (e.g., phenoxybenzamine) before any beta-blocker in suspected pheochromocytoma |
| Reversible mental depression progressing to catatonia (post-marketing) | Very rare | Variable | Discontinuation; reversible per PI |
| Agranulocytosis, thrombocytopenic purpura, nonthrombocytopenic purpura (post-marketing) | Very rare | Variable | Discontinue; haematology assessment |
| Worsening peripheral arterial insufficiency | Uncommon; gangrene reported in patients with severe pre-existing disease | Variable | Assess claudication and distal perfusion; consider switch to a vasodilating beta-blocker (carvedilol, nebivolol) if symptomatic |
| Reason for Discontinuation | Relative Frequency | Context |
|---|---|---|
| Fatigue / exercise intolerance | Most common tolerability reason | Often improves over 2–4 weeks; consider dose reduction before discontinuation. |
| Symptomatic bradycardia or hypotension | Modest | More common with concomitant non-DHP calcium channel blockers, digoxin, or strong CYP2D6 inhibitors. |
| Worsening HF during titration | Reported in HF trials | Often resolved by adjusting diuretic and slowing the up-titration schedule rather than stopping. |
| Sexual dysfunction | Less common but underreported | Class effect of beta-blockers; switching to a vasodilating beta-blocker (nebivolol) may help. |
| Bronchospasm | Uncommon at low doses | Reversible; switch to a non-beta-blocker antihypertensive class if recurrent. |
Symptomatic bradycardia (HR <50 bpm with light-headedness, fatigue, or hypotension) usually responds to dose reduction or temporary withdrawal. Severe bradycardia, marked hypotension, or new high-grade AV block should prompt immediate withdrawal and supportive care: IV atropine, IV fluids, transcutaneous pacing for severe AV block, and IV glucagon (3–10 mg bolus, then infusion) for refractory beta-blocker toxicity. For worsening heart failure during titration, increase the diuretic and restore stability before slowing or pausing the up-titration; do not abandon the drug — late benefit accrues even after a delayed schedule.
Drug Interactions
Metoprolol is metabolised primarily by CYP2D6, making it susceptible to a clinically important pharmacokinetic interaction with strong CYP2D6 inhibitors. Per the FDA prescribing information, quinidine doubled metoprolol concentrations and tripled S-metoprolol; propafenone increased steady-state metoprolol concentration 2- to 5-fold. Pharmacodynamic interactions — additive bradycardia, AV nodal slowing, or hypotension — are equally important and arise commonly with cardiology drug combinations.
The single most easily missed interaction is with strong CYP2D6 inhibitors — particularly paroxetine, fluoxetine, and bupropion, which are commonly co-prescribed in patients with depression and cardiac disease. When initiating or up-titrating metoprolol in a patient on one of these agents, expect higher exposure and start lower. Conversely, a patient stable on metoprolol who develops new bradycardia or fatigue may have recently started a CYP2D6 inhibitor.
Monitoring
-
Heart Rate
Baseline, at each titration step, then at each follow-up
Routine Target resting HR generally 55–70 bpm depending on indication. Symptomatic bradycardia (HR <50 bpm with light-headedness or fatigue) prompts dose reduction or temporary withdrawal. In heart failure, asymptomatic HR in the 50s is acceptable and often desirable. -
Blood Pressure
Baseline, at each titration step, then at each follow-up
Routine Check both seated and standing. Symptomatic orthostasis or SBP <100 mmHg in a non-acute setting prompts dose reassessment. For hypertension on once-daily dosing, also assess BP near the end of the dosing interval to confirm 24-hour control. -
Heart Failure Signs (in HF patients)
Each titration step (every 2 weeks during initiation)
Routine Weight, dyspnoea, oedema, JVP, lung crackles. Worsening signs during titration should prompt diuretic adjustment and slowing — not abandonment — of the titration schedule. -
ECG
Baseline; repeat if symptomatic bradycardia or new conduction symptoms
Trigger-based Check for first-degree AV block, second/third-degree AV block, sinus bradycardia, or sinus pauses. Pre-existing PR ≥0.24 sec is a contraindication to the IV regimen in acute MI. -
Glycaemic Status (in diabetics)
As per usual diabetic care
Routine Counsel that adrenergic warning signs of hypoglycaemia (tachycardia, tremor) may be blunted; sweating is generally preserved. Insulin-treated patients warrant attention to hypoglycaemia awareness, particularly during fasting, surgery, or intercurrent illness. -
Respiratory Symptoms
At each visit
Routine In patients with reactive airways disease, monitor for bronchospasm, particularly during dose escalation when β1-selectivity attenuates. Have a rescue inhaler available. -
Mood and Sleep
At each visit (open-ended enquiry)
Routine Vivid dreams, sleep disturbance, and depressive symptoms are CNS-related effects of lipophilic beta-blockers. Switching to a less lipophilic agent (atenolol, nadolol, bisoprolol) may help if these become problematic. -
Sexual Function
At each follow-up (open-ended enquiry)
Routine Often underreported by patients. A vasodilating beta-blocker (nebivolol) may have a more favourable sexual side-effect profile if this becomes a barrier to adherence. -
Liver Function (in hepatic impairment)
Baseline if hepatic disease suspected
Trigger-based Routine LFTs not required, but baseline hepatic status informs dosing — extensively first-pass-metabolised drugs accumulate substantially in poor hepatic function. Post-marketing reports include elevated transaminases. -
Adherence
At each follow-up
Routine Particularly important because abrupt withdrawal — including from missed doses or running out of supply — can precipitate ischaemia in CAD, rebound hypertension, or arrhythmia.
For routine metoprolol monitoring, two vitals dominate: heart rate and blood pressure, checked at every titration step and at each follow-up. Once patients are at maintenance dose with stable vitals, follow-up at 3–6 months is typically sufficient unless new symptoms, concomitant medication changes, or comorbid conditions arise.
Contraindications & Cautions
Absolute Contraindications (per Lopressor PI)
- Severe bradycardia
- Second- or third-degree atrioventricular block (unless a permanent pacemaker is in place)
- Sick sinus syndrome (unless a permanent pacemaker is in place)
- Cardiogenic shock
- Systolic blood pressure <100 mmHg
- Decompensated heart failure
- Hypersensitivity to metoprolol or any component of the product (cross-sensitivity between beta-blockers can occur)
- For acute MI tartrate IV regimen additionally: heart rate <45 bpm, significant first-degree AV block (PR ≥0.24 s), and hypersensitivity to other beta-blockers
Untreated pheochromocytoma is not listed as an absolute contraindication in the Lopressor PI but the PI requires that an alpha-blocker be initiated first; administration of a beta-blocker alone in this setting can cause a paradoxical hypertensive response.
Relative Contraindications (Specialist Input Recommended)
- Bronchospastic disease (asthma, severe COPD) — generally avoid; if needed, use lowest effective dose of cardioselective metoprolol with bronchodilator readily available. Patients with mild-to-moderate stable COPD often tolerate cardioselective beta-blockers
- Severe peripheral vascular disease with critical limb ischaemia or rest pain — beta-blockade may aggravate symptoms; consider a vasodilating beta-blocker (nebivolol, carvedilol)
- Prinzmetal (vasospastic) angina — unopposed alpha-mediated coronary vasoconstriction may worsen vasospasm; calcium channel blockers are preferred
- Severe hepatic impairment — substantially elevated plasma exposure; if used, start at lower than usual dose
- Pregnancy — not absolutely contraindicated and frequently used when treatment is necessary, but crosses placenta; monitor neonate for bradycardia, hypoglycaemia, hypotension, and respiratory depression at and after delivery
Use with Caution
- Diabetes mellitus — masks adrenergic hypoglycaemia warning signs and may prolong hypoglycaemia; risk is higher with fasting, surgery, vomiting, or in children. Cardioselective metoprolol is preferred to non-selective beta-blockers in diabetics
- Thyrotoxicosis — useful for adrenergic symptom control but masks tachycardia. Withdraw gradually after definitive therapy to avoid precipitating thyroid storm
- Anaphylaxis history — beta-blockade may blunt the response to adrenaline used for treatment; higher adrenaline doses or IV glucagon may be needed
- Major surgery — abrupt withdrawal can precipitate perioperative myocardial ischaemia; continue chronic beta-blocker through the perioperative period whenever feasible. Avoid initiation of a high-dose regimen of beta-blocker therapy shortly before non-cardiac surgery in beta-blocker–naïve patients (POISE)
- Concurrent non-DHP calcium channel blocker therapy — additive AV nodal slowing; combine cautiously and only when clinically indicated
Metoprolol does not carry an FDA boxed warning. The FDA prescribing information emphasises the risk of acute exacerbation of myocardial ischaemia or precipitation of MI on abrupt withdrawal in patients with known coronary disease — therapy should be tapered over 1–2 weeks rather than stopped suddenly. The PI also flags worsening cardiac failure during heart-failure up-titration, requires alpha-blocker initiation before any beta-blocker in pheochromocytoma, warns of the risk of severe or prolonged hypoglycaemia (especially in fasting / surgical patients and children), and warns of attenuated response to adrenaline used for anaphylaxis treatment.
Class-wide perioperative caution: routine initiation of a high-dose beta-blocker regimen shortly before non-cardiac surgery in beta-blocker–naïve patients is associated with increased mortality (POISE trial) and is no longer recommended. However, patients on chronic metoprolol should generally continue therapy through the perioperative period to avoid withdrawal-related ischaemia.
Patient Counselling
Purpose of Therapy
Explain that metoprolol is a “beta-blocker” — a long-established medicine that slows the heart, lowers blood pressure, and reduces the workload on the heart. Depending on the indication, it is used to treat high blood pressure, chest pain (angina), heart failure, irregular heart rhythms, or to protect the heart after a heart attack. The benefit accrues over time and depends on consistent dosing — particularly in heart failure, where the long-term mortality benefit is one of the largest seen for any cardiovascular medication.
How to Take
The two formulations are taken differently. Metoprolol tartrate (Lopressor) is the immediate-release form, usually taken twice a day, with food or immediately after a meal — once in the morning and once in the evening. Metoprolol succinate (Toprol-XL) is the extended-release form, taken once a day at the same time each day; the tablet may be split along the scoreline if needed but should not be chewed or crushed. Both forms work best when taken consistently. Do not stop taking metoprolol abruptly — even if you feel well — because suddenly stopping can cause chest pain, a fast or irregular heartbeat, or in some cases a heart attack. If you need to stop, your prescriber will guide you through a 1–2 week taper.
Sources
- U.S. Food and Drug Administration. Lopressor (metoprolol tartrate) prescribing information (revised July 2023). Validus Pharmaceuticals LLC. FDA label PDF Primary source for tartrate dosing in hypertension, angina, and acute MI; specific adverse-event rates in the MI trial; CYP2D6 interaction quantification; and contraindications.
- U.S. Food and Drug Administration. Toprol-XL (metoprolol succinate) extended-release tablets prescribing information. FDA label PDF Primary source for succinate dosing including the heart-failure indication, paediatric hypertension dosing, and the relative bioavailability comparison with tartrate.
- U.S. Food and Drug Administration. Metoprolol succinate extended-release capsules prescribing information. FDA label PDF Capsule formulation prescribing information — confirms equivalence of dosing scheme and key warnings across succinate presentations.
- U.S. Food and Drug Administration. Metoprolol tartrate injection prescribing information. Pfizer. IV labelling IV-specific contraindications, hold criteria, and post-IV oral transition guidance.
- Hjalmarson A, Herlitz J, Malek I, et al. Effect on mortality of metoprolol in acute myocardial infarction. A double-blind randomised trial (Göteborg Metoprolol Trial). Lancet. 1981;2(8251):823-827. DOI: 10.1016/s0140-6736(81)91101-6 The 1,395-patient placebo-controlled trial cited in the Lopressor PI as the basis for the acute MI mortality indication; demonstrated a 36% reduction in 3-month mortality.
- MERIT-HF Study Group. Effect of metoprolol CR/XL in chronic heart failure: Metoprolol CR/XL Randomised Intervention Trial in Congestive Heart Failure (MERIT-HF). Lancet. 1999;353(9169):2001-2007. DOI: 10.1016/S0140-6736(99)04440-2 Pivotal heart failure trial — 3,991 NYHA II–IV patients with LVEF ≤0.40; significant reduction in all-cause mortality led to early trial termination. Basis for the FDA heart-failure indication of metoprolol succinate.
- Hjalmarson A, Goldstein S, Fagerberg B, et al. Effects of controlled-release metoprolol on total mortality, hospitalizations, and well-being in patients with heart failure: the Metoprolol CR/XL Randomized Intervention Trial in Congestive Heart Failure (MERIT-HF). JAMA. 2000;283(10):1295-1302. DOI: 10.1001/jama.283.10.1295 Companion publication of MERIT-HF outcomes, including mortality, hospitalisation, and quality-of-life endpoints.
- MIAMI Trial Research Group. Metoprolol in acute myocardial infarction (MIAMI). A randomised placebo-controlled international trial. Eur Heart J. 1985;6(3):199-226. DOI: 10.1093/oxfordjournals.eurheartj.a061845 5,778-patient acute MI trial — showed a numerically smaller, non-significant reduction in 15-day mortality; provides additional context for the early-IV-followed-by-oral metoprolol regimen.
- Chen ZM, Pan HC, Chen YP, et al. Early intravenous then oral metoprolol in 45,852 patients with acute myocardial infarction: randomised placebo-controlled trial (COMMIT). Lancet. 2005;366(9497):1622-1632. DOI: 10.1016/S0140-6736(05)67661-1 Large trial demonstrating that early IV metoprolol in acute MI reduced reinfarction and ventricular fibrillation but increased cardiogenic shock — the basis for current cautious patient selection.
- POISE Study Group; Devereaux PJ, Yang H, Yusuf S, et al. Effects of extended-release metoprolol succinate in patients undergoing non-cardiac surgery (POISE). Lancet. 2008;371(9627):1839-1847. DOI: 10.1016/S0140-6736(08)60601-7 Defines the perioperative caution against routine initiation of a high-dose beta-blocker regimen in beta-blocker–naïve patients shortly before non-cardiac surgery.
- Heidenreich PA, Bozkurt B, Aguilar D, et al. 2022 AHA/ACC/HFSA guideline for the management of heart failure. J Am Coll Cardiol. 2022;79(17):e263-e421. DOI: 10.1016/j.jacc.2021.12.012 Defines the role of metoprolol succinate as one of three evidence-based beta-blockers (with bisoprolol and carvedilol) for heart failure with reduced ejection fraction.
- Whelton PK, Carey RM, Aronow WS, et al. 2017 ACC/AHA/AAPA/ABC/ACPM/AGS/APhA/ASH/ASPC/NMA/PCNA guideline for the prevention, detection, evaluation, and management of high blood pressure in adults. J Am Coll Cardiol. 2018;71(19):e127-e248. DOI: 10.1016/j.jacc.2017.11.006 Beta-blockers including metoprolol are not first-line for uncomplicated hypertension but are appropriate when there is a compelling indication (post-MI, HF, AF, angina).
- Joglar JA, Chung MK, Armbruster AL, et al. 2023 ACC/AHA/ACCP/HRS guideline for the diagnosis and management of atrial fibrillation. J Am Coll Cardiol. 2024;83(1):109-279. DOI: 10.1016/j.jacc.2023.08.017 Recommends beta-blockers including metoprolol as first-line for rate control in atrial fibrillation across the LVEF spectrum.
- Silberstein SD, Holland S, Freitag F, et al. Evidence-based guideline update: pharmacologic treatment for episodic migraine prevention in adults. Neurology. 2012;78(17):1337-1345. DOI: 10.1212/WNL.0b013e3182535d20 AAN/American Headache Society guideline classifying metoprolol as Level A (established as effective) for migraine prophylaxis, alongside propranolol and timolol.
- Blake CM, Kharasch ED, Schwab M, Nagele P. A meta-analysis of CYP2D6 metabolizer phenotype and metoprolol pharmacokinetics. Clin Pharmacol Ther. 2013;94(3):394-399. DOI: 10.1038/clpt.2013.96 Quantifies the impact of CYP2D6 phenotype on metoprolol exposure across published studies; supports cautious dose escalation in poor metabolisers and patients on strong CYP2D6 inhibitors.
- Lymperopoulos A, Garcia D, Walklett K. Pharmacogenetics of beta-blockers in heart failure. Curr Med Chem. 2014;21(17):1888-1897. StatPearls: Metoprolol Reference summary for CYP2D6 polymorphism considerations (link points to the open-access StatPearls metoprolol chapter, which compiles the relevant pharmacology and is freely accessible).