What happens if a sustained-release (SR) metoprolol (beta-blocker) tablet is crushed and administered?

Crushing Sustained-Release Metoprolol: Risks and Consequences

Crushing sustained-release metoprolol tablets leads to immediate release of the full dose, potentially causing dangerous cardiovascular effects including severe hypotension, bradycardia, and risk of cardiovascular collapse. 1

Pharmacological Consequences of Crushing

• Crushing metoprolol succinate modified-release tablets significantly alters their dissolution profile, causing rapid and uncontrolled drug release rather than the intended 20-24 hour controlled release 1
• Dissolution studies show statistically significant differences between crushed and whole tablets across various pH environments (pH 4.5 and pH 6.8), confirming that crushing destroys the controlled-release mechanism 1
• Crushing damages the specialized micropellets embedded in the tablet that are designed to release the medication gradually over approximately 20 hours 1, 2

Clinical Risks

• Rapid release of the full metoprolol dose can cause:

  • Severe bradycardia and hypotension 3
  • Direct myocardial depression 3
  • Potential for cardiovascular collapse requiring emergency interventions 3
  • Increased risk of adverse effects related to high peak plasma concentrations 2

• The risk is particularly high for:

  • Patients with heart failure or low cardiac output 4
  • Patients with PR interval >0.24 seconds 4
  • Patients with second or third-degree heart block 4
  • Patients with active asthma or reactive airways disease 4
  • Elderly patients or those with existing cardiovascular compromise 5

Formulation Differences

• Metoprolol succinate (extended-release) is specifically designed to maintain consistent plasma concentrations over 24 hours 2, 6
• After ingestion, intact tablets disintegrate into individual pellets with each pellet acting as a diffusion cell releasing drug at a relatively constant rate 6
• Crushing destroys this carefully engineered delivery system, converting a once-daily medication into an immediate-release formulation 1
• A 100-mg metoprolol controlled/extended-release tablet contains 95 mg of metoprolol succinate and is equivalent to 100 mg metoprolol tartrate in total daily dose, but with completely different release characteristics 6

Clinical Implications

• Patients receiving crushed metoprolol succinate through feeding tubes may experience unpredictable plasma concentration profiles, potentially affecting clinical outcomes 1
• Overdose symptoms from rapid release may include severe bradycardia, hypotension, and in extreme cases, cardiac arrest 3, 7
• Treatment of adverse effects from rapid release may require glucagon, atropine, vasopressors, and in severe cases, advanced cardiac life support measures 3

Recommendations

• Sustained-release metoprolol formulations should never be crushed 1

• For patients with swallowing difficulties or feeding tubes requiring beta-blocker therapy, consider:

  • Using immediate-release metoprolol tartrate at appropriate divided doses 4
  • Consulting with a pharmacist for appropriate alternative formulations 1
  • Using alternative beta-blockers available in liquid formulations when appropriate 5

• If beta-blockade is required in patients unable to take oral medications, IV metoprolol can be administered at 5 mg over 1-2 minutes, repeated as required every 5 minutes to a maximum dose of 15 mg, with careful titration according to heart rate and blood pressure response 4