Metoprolol is the selective β1 receptor blocker. Metoprolol is safer in patient which has bronchoconstriction with propranolol. It is also safer drug in patient with diabetes, COPD and peripheral vascular disease.
GENERIC NAME: Metoprolol
BRAND NAME: Lopressor, Toprol
MECHANISM OF ACTION
Metoprolol has modest non-selective β1 selectivity and possess very low intrinsic sympathomimetic activity (ISA). Metoprolol blocks the β1 receptor resulting in inhibition of sympathetic nervous system thus, decreased heart rate, delayed conduction through AV node, and reduced contractility which finally decreased the cardiac output and oxygen demand by heart muscles.
Metoprolol can use in patient with the history of asthma with caution. Metoprolol is also the drug of choice in patient with diabetes and peripheral vascular disease.
PHARMACOKINETICS
Metoprolol is well absorbed after oral administration. Peak concentration occur 1-3 hours after orally taken. It has moderate lipid solubility. It is rapidly distributed in the system. It is extensively metabolized in the liver and has bioavailability of 50%. Metoprolol is excreted little unchanged in the urine. Elimination half-life is 3-4 hours.
INDICATIONS
- Hypertension
- Ischemic heart disease
- Cardiac arrhythmias
- Heart failure
- Following Myocardial infarction
- Dissecting aneurysm (Esmolol)
- Glaucoma
- Migraine prophylaxis
- Hyperthyroidism
- Essential tremors
CONTRAINDICATIONS
- Hypersensitivity
- Renal failure (Atenolol)
- Decompensated heart failure
- Peripheral vascular disease
- Raynaud’s phenomenon
- Bradyarrythmia
SIDE EFFECTS & ADVERSE EFFECTS
- Insomnia
- Intolerance include fatigue, cold extremities, erectile dysfunction
- Asthma or COPD (with non-selective beta blockers)
- Hypoglycemia (insulin dependent diabetic patient)
- Heart block
- Metabolic disturbance
- Others include
- Rash
- Blurred vision
- Weakness
- Muscle cramps
- Headache
- Nausea vomiting
- Confusion
- Pheochromocytoma
DRUG INTERACTION
- Antacids and antidiarrhoeals may cause slight increase in the absorption of metoprolol but this effect is clinically not significant.
- Most NSAIDs can increase blood pressure when given with metoprolol including piroxicam, Indometacin, ibuprofen, naproxen. Celecoxib reduce the metabolism of metoprolol.
- Barbiturates effected the plasma level and action of metoprolol that is metabolized by liver
- The use of concurrent use of metoprolol and dihydropyridine type calcium channel blockers appeared to be safe and useful clinically e.g. felodipine, irsadipine, lacidipine, nicardipine, nimodipine. Although Nifedipine and nifoldipine may cause severe hypotension and heart failure when given with metoprolol.
- Diltiazem may enhance the antihypertensive effects of metoprolol and clinically significant when given concurrently but close monitoring is necessary.
- Verapamil may enhance the antihypertensive effects of metoprolol and clinically significant when given concurrently but close monitoring is necessary.
- Bupropion may cause bradycardia and severe hypotension when given with metoprolol.
- Dextropropoxyphene may increase the bioavailability of metoprolol when given concurrently.
- The concurrent use of ergot derivatives and metoprolol in the management of migraine may cause severe peripheral vasoconstriction and hypertension.
- Fish oil may enhance the hypotensive effects of metoprolol.
- The concurrent use of flecainide and metoprolol may cause additive cardiac depressant effects
- Food may increase, decrease or no change to the metoprolol but it has no clinically significance.
- Cimetidine may cause irregular heart beat when given with metoprolol.
- Intraocular acetylcholine may cause when given with metoprolol.
- Tobacco smoking may reduce the beneficial effects of metoprolol i.e. heart rate and blood pressure.
- Rifampicin may increase the clearance of metoprolol when given concurrently
- Propafenone may increase the plasma level (two to five fold) metoprolol which can increase toxicity.
- Metoprolol may cause anaphylactic reactions of penicillin when given concurrently.
NURSING INTERVENTIONS
- Inquire patient’s complete health history including allergies, diabetes or any respiratory diseases
- Monitor blood pressure and pulse prior administration of medicine. If blood pressure and pulse is not in normal range inform the health practitioner.
- Observe daily intake an output of fluid. Check body weight.
- If patient is on parenteral drug then check blood pressure and pulse frequently.
- Patient with respiratory disease specially with asthma or COPD should be closely monitored for sign and symptoms.
- Observe lab determining electrolytes, BUN, creatinine levels.
- In diabetic patient observe hypoglycemic effects
PATIENT EDUCATION
- Counsel the right dose and time of medicine.
- If patient is taking metoprolol then counsel patient to take with meal or after meal.
- Don’t break, crush or dissolve sustained release medicine.
- Counsel them the possible side effects of medicine.
- If blood pressure or pulse is too low then immediate contact to the doctors
- Change position slowly to avoid orthostatic hypotension
- Ask doctor prior to take any multivitamins or any supplements
- Report immediately to the doctor if feeling chest pain, SOB, faintness with exercise or during work activities.