24B09: Exam Report

Compare and contrast metoprolol and verapamil using the following headings

  1. Class and indications for use (20% of marks).

  2. Mechanisms of action (25% of marks).

  3. Pharmacodynamics and adverse effects (55% of marks).

21% of candidates passed this question.

The most effective format for this question was to split information into the headings provided.

The higher scoring responses were done as a table, with headings as per the question, concise facts and clear comparisons.

Information on pharmaceutics, dose and pharmacokintetics were not required.

When effects of the drugs were discussed detail regarding the mechanism of pharmacodynamics and adverse effects was expected.

Cardiovascular effects of these drugs required specificity in their description and included their action on the duration and slope of the cardiac action potential thus affecting the HR, as well as effects on SVR and BP.

Other adverse effects included respiratory, neurological and gastrointestinal actions.

G7iii / 24B09: Compare and contrast metoprolol and verapamil using the following headings

V – W classify antiarrhythmic in groups based on electrophysiological characteristics → based on micro-electrode studies

Class

Metoprolol

  • Beta blocker
  • Cardio selective (B1>B2)
  • Membrane stabilising property +
  • Intrinsic sympathomimetic activity

Verapamil

  • CCB / VW Class IV antiarrhythmic
  • Type I : Phenylalkylamines

INDICATIONS

Metoprolol

  • MI- decreases infarct size, VF
  • AF
  • HTN

Verapamil

  • HTN
  • Angina
  • SVT, AF, AFl

MoA

Metoprolol

  • Binds to Gs-protein coupled β1 receptors, blocks cAMP synthesis
  • Anatgonises effects of catecholamines

Verapamil

PD - CVS

Metoprolol

  • AP – Duration, slope >> HR- reduced
  • SV / CO– Reduced
  • SVR – reduced
  • BP – reduced
  • VO2 – reduced

Verapamil

  • Reduces –
  • Automaticity
  • Conduction, specifically at AVN
  • Increases refractory period
  • Decreases contractility

PD - RS

Metoprolol

  • Little effect since cardioselective

  • Bronchospasm at high doses

Verapamil

PD - CNS

Metoprolol

  • Moderately lipophilic – low incidence of neuropsychiatric side effects

Verapamil

  • Cerebral vasodilation

PD - AE

Metoprolol

  • Mainly cardiovascular
    • Bradycardia
    • Complete heart block (caution with CCBs)
    • Hypotension
    • Glucose intolerance
  • Withdrawal
    • Tachycardia
    • Hypertension

Verapamil

  • Heart block
  • Heart failure
  • Flushing
  • Dizziness,
  • Precipitate VT/VF in WPW syndrome

Author: Nazma Navilehal Rajasab