Metoprolol

Metoprolol - is a selective β1-adrenoreceptor blocking agent; this preferential effect is not absolute, however, and at higher doses it also inhibits β2-adrenoreceptors. Plasma levels following oral administration are approximately 50% of levels following IV administration, indicating about 50% first-pass metabolism. For dose conversion purposes, equivalent maximal beta-blocking effect is achieved with oral and IV doses in the ratio of approximately 2.5:1.Metoprolol is eliminated mainly by biotransformation in the liver, and the plasma half-life ranges from approximately 3 to 7 hours. Hence, no reduction in dosage is usually needed in patients with renal failure.

Uses
Hypertension
Angina pectoris
Control of tachyarrhythmias
Myocardial infarction

Contraindications
Asthma (worsens unless compelling reasons for use)
Second- or third-degree heart block
Decompensated cardiac failure (pulmonary oedema, hypoperfusion or hypotension)

Administration
Orally: usually 25–50 mg 8–12 hourly
IV bolus: initially up to 5 mg at a rate of 1–2 mg/min; can be repeated at 5-min intervals until a satisfactory response. A total dose
of 10–15 mg generally proves sufficient
IV infusion (unlicensed): dilute 20 mg in 50 ml of sodium chloride 0.9% or glucose 5%. Starting dose 0.04 mg/kg/h and titrate to
response, usually up to 0.1 mg/kg/h

Adverse effects
Bradycardia
Heart failure
Postural hypotension

Cautions
Subject to enzyme inducers and inhibitors
Increased negative inotropic and chronotropic effects may occur when metoprolol is given with verapamil and diltiazem.Avoid IV verapamil in patients treated with beta-blockers

Organ failure
Hepatic: reduce dose