What are the potential side effects of metoprolol (beta blocker)?

Potential Side Effects of Metoprolol

Metoprolol is generally well tolerated with an overall favorable safety profile, but clinicians must monitor for hypotension and bradycardia as dose-limiting adverse effects, particularly during initiation and uptitration. 1, 2

Common Side Effects (Occurring in ≥1% of Patients)

Cardiovascular Effects

• Hypotension occurs in approximately 1% of patients with hypertension/angina, but increases to 27.4% in myocardial infarction patients 2
• Bradycardia (heart rate <40 bpm) affects approximately 3% of hypertension/angina patients but increases to 15.9% in MI patients 2
• Heart block: First-degree AV block (5.3%), second- or third-degree heart block (4.7%) 2
• Cold extremities, arterial insufficiency (Raynaud-type), palpitations, peripheral edema occur in approximately 1% of patients 2
• Congestive heart failure may be precipitated or worsened, occurring in about 1% of patients 2

Central Nervous System Effects

• Tiredness and dizziness are the most common CNS effects, occurring in approximately 10% of patients 2
• Depression affects approximately 5% of patients 2
• Headache, nightmares, insomnia have been reported 2
• Mental confusion and short-term memory loss occur less frequently 2

Respiratory Effects

• Bronchospasm and dyspnea occur in approximately 1% of patients 2
• Beta-blockers can aggravate bronchospastic symptoms in asthma patients, though metoprolol's beta-1 selectivity may be lost at higher doses 1
• Most patients with COPD without a bronchospastic component tolerate beta-blockade well 1

Gastrointestinal Effects

• Diarrhea occurs in approximately 5% of patients 2
• Nausea, dry mouth, gastric pain, constipation, flatulence, heartburn each occur in approximately 1% of patients 2
• Vomiting is a common occurrence 2

Dermatologic Effects

• Pruritus or rash occur in approximately 5% of patients 2
• Very rare reports of photosensitivity and worsening of psoriasis 2

Serious but Rare Side Effects

Cardiovascular Complications

• Cardiogenic shock can occur, particularly in high-risk patients (age >70 years, systolic BP <120 mmHg, heart rate >110 or <60 bpm) 3
• Cardiac arrest has been reported with metoprolol use 2
• Gangrene in patients with pre-existing severe peripheral circulatory disorders (very rare) 2

Hepatic Effects

• Very rare reports of hepatitis, jaundice, and non-specific hepatic dysfunction 2
• Isolated cases of transaminase, alkaline phosphatase, and lactic dehydrogenase elevations 2

Hematologic Effects

• Rare reports of agranulocytosis 2
• Nonthrombocytopenic purpura and thrombocytopenic purpura (potential adverse reactions) 2

Other Rare Effects

• Reversible alopecia (hair loss) 2
• Peyronie's disease (fewer than 1 in 100,000 patients) 2
• Musculoskeletal pain, blurred vision, tinnitus, dry eyes 2
• Very rare reports of weight gain, arthritis, retroperitoneal fibrosis 2

Critical Clinical Monitoring Points

During Initiation and Uptitration

• Monitor heart rate and blood pressure before each dose to assess for excessive bradycardia or hypotension 4
• Significant hemodynamic effects occur within 2-4 hours of oral administration 4
• Use a "start-low, go-slow" approach to minimize adverse effects 1

Special Populations Requiring Enhanced Monitoring

Patients at High Risk for Cardiogenic Shock:

• Monitor especially carefully during the 2-4 hour peak period after administration 4
• Risk factors include: decompensated heart failure, severe bradycardia, marked first-degree AV block 4, 3

Patients with Diabetes:

• Beta-blockers may mask tachycardia occurring with hypoglycemia, though dizziness and sweating remain 2

Patients with Peripheral Vascular Disease:

• While metoprolol's beta-1 selectivity makes it relatively safer, monitor for worsening claudication 1
• One study showed pain-free walking distance actually increased with metoprolol treatment 5

Children and Adolescents:

• Moderate doses may affect growth or impair school performance 1
• May trigger depression and should be closely monitored 1

Important Caveats

Loss of Beta-1 Selectivity

• Both metoprolol tartrate and bisoprolol may lose their beta-1 selectivity when prescribed in doses associated with survival improvement in heart failure 1
• This increases the risk of bronchospasm in susceptible patients 1

Withdrawal Considerations

• Never abruptly discontinue metoprolol in patients with coronary artery disease 2
• Severe exacerbation of angina, myocardial infarction, and ventricular arrhythmias have been reported with abrupt discontinuation 2
• Taper gradually over 1-2 weeks when discontinuing 2

Drug-Specific Tolerability

• The overall safety profile of beta-blockers warrants their use despite modest effectiveness and potential for hypotension as a dose-limiting factor 1
• Metoprolol is generally well tolerated with temporary fatigue, dizziness, and headache being the most frequently reported side effects 6