METOPROLOL

“LOPRESOR”

1) Action

• Selective Beta Adrenergic Blocker [Class II antiarrhythmic]

2) Mechanism

• Antagonises catecholamines at b1 adrenoreceptors [to a much lesser degree than propranolol it blocks b2 adrenoreceptors

• Ameliorates hypertension by: reduction of CO, reduction of SVR, inhibition of the renin production by catecholamines (mediated by b1 receptors)

3) Indications

• Angina pectoris (decrease cardiac work & reduce oxygen demand)

• Myocardial infarction

• Hypertension

• Arrhythmias [may convert AF & Af to SR, reduce PVCs]

• Migraines

• May be used in hypertensive patients suffering from asthma or diabetes

5) Toxic effects/ precautions with administration

• Caution when used with calcium channel blockers

• Caution when given to diabetics

• Caution when given to asthmatics

• May reduce sympathetic response during myocardial depressive drugs given during anaesthesia

6) Contraindications

• CCF: patients depends on sympathetic drive to maintain CO

• Sinus bradycardia; heart blocks

• Asthma; bronchospasm

• Right ventricular hypertrophy 2° pulmonary hypertension

7) Reversal, antagonism or antidote

• Hypotension: Adrenaline, Noradrenaline

• Bradycardia: Atropine, glucagon

• Cardiac failure: digoxin

• Bronchospasm: isoprenaline, aminophylline

8) Loading dose, maintenance dose, frequency & method of administration

• Oral, IV

• 1mg/1ml ampoule

9) Drug’s metabolism—Drug’s excretion—Half life (pharmacokinetics)

• Elimination half life: 3-4 hours

• Metabolised in liver