displayName: CLINICAL PHARMACOLOGY SECTION
FDA Article Code: 34090-1
Mechanism of Action
Metoprolol tartrate is a beta
1-selective (cardioselective) adrenergic receptor blocker. This preferential effect is not absolute, however, and at higher plasma concentrations, metoprolol also inhibits beta
2-adrenoreceptors, chiefly located in the bronchial and vascular musculature.
Clinical pharmacology studies have demonstrated the beta-blocking activity of metoprolol, as shown by (1) reduction in heart rate and cardiac output at rest and upon exercise, (2) reduction of systolic blood pressure upon exercise, (3) inhibition of isoproterenol-induced tachycardia, and (4) reduction of reflex orthostatic tachycardia.
The mechanism of the antihypertensive effects of beta-blocking agents has not been fully elucidated. However, several possible mechanisms have been proposed: (1) competitive antagonism of catecholamines at peripheral (especially cardiac) adrenergic neuron sites, leading to decreased cardiac output; (2) a central effect leading to reduced sympathetic outflow to the periphery; and (3) suppression of renin activity.
By blocking catecholamine-induced increases in heart rate, in velocity and extent of myocardial contraction, and in blood pressure, metoprolol reduces the oxygen requirements of the heart at any given level of effort, thus making it useful in the long-term management of angina pectoris.
The precise mechanism of action of metoprolol in patients with suspected or definite myocardial infarction is not known.
1 selectivity is demonstrated by the following: (1) In healthy subjects, metoprolol is unable to reverse the beta
2-mediated vasodilating effects of epinephrine. This contrasts with the effect of nonselective (beta
1 plus beta
2) beta-blockers, which completely reverse the vasodilating effects of epinephrine. (2) In asthmatic patients, metoprolol reduces FEV
1 and FVC significantly less than a nonselective beta-blocker, propranolol, at equivalent beta
1-receptor blocking doses.
Metoprolol has no intrinsic sympathomimetic activity, and membrane-stabilizing activity is detectable only at doses much greater than required for beta-blockade. Animal and human experiments indicate that metoprolol slows the sinus rate and decreases AV nodal conduction.
Significant beta-blocking effect (as measured by reduction of exercise heart rate) occurs within 1 hour after oral administration, and its duration is dose-related. For example, a 50% reduction of the maximum effect after single oral doses of 20, 50, and 100 mg occurred at 3.3, 5, and 6.4 hours, respectively, in normal subjects. After repeated oral dosages of 100 mg twice daily, a significant reduction in exercise systolic blood pressure was evident at 12 hours. When the drug was infused over a 10-minute period, in normal volunteers, maximum beta-blockade was achieved at approximately 20 minutes. Equivalent maximal beta-blocking effect is achieved with oral and intravenous doses in the ratio of approximately 2.5:1.
There is a linear relationship between the log of plasma levels and reduction of exercise heart rate. However, antihypertensive activity does not appear to be related to plasma levels. Because of variable plasma levels attained with a given dose and lack of a consistent relationship of antihypertensive activity to dose, selection of
proper dosage requires individual titration.
In several studies of patients with acute myocardial infarction, intravenous followed by oral administration of metoprolol caused a reduction in heart rate, systolic blood pressure and cardiac output. Stroke volume, diastolic blood pressure and pulmonary artery end diastolic pressure remained unchanged.
In patients with angina pectoris, plasma concentration measured at 1 hour is linearly related to the oral dose within the range of 50 to 400 mg. Exercise heart rate and systolic blood pressure are reduced in relation to the logarithm of the oral dose of metoprolol. The increase in exercise capacity and the reduction in left ventricular ischemia are also significantly related to the logarithm of the oral dose.
displayName: OVERDOSAGE SECTION
FDA Article Code: 34088-5
Several cases of overdosage have been reported, some leading to death.
50’s (mg/kg): mice, 1158 to 2460; rats, 3090 to 4670.
displayName: HOW SUPPLIED SECTION
FDA Article Code: 34069-5
Metoprolol Tartrate Tablets, USP are available as follows:
Tablets 25 mg are white round shaped, film coated tablets debossed with ‘C over 73’ on one side and deep break line on other side.
Bottles of 100 NDC 59762-1300-1 (Child Resistant Closure)
Bottles of 1000 NDC 59762-1300-3 (Non Child Resistant Closure)
Tablets 50 mg are pink round shaped, film coated tablets debossed with ‘C over 74’ on one side and deep break line on other side.
Bottles of 100 NDC 59762-1301-1 (Child Resistant Closure)
Bottles of 1000 NDC 59762-1301-3 (Non Child Resistant Closure)
Tablets 100 mg are light blue round shaped, film coated tablets debossed with ‘C over 75’ on one side and deep break line on other side.
Bottles of 100 NDC 59762-1302-1 (Child Resistant Closure)
Bottles of 1000 NDC 59762-1302-3 (Non Child Resistant Closure)
Store at 20° to 25°C (68° to 77°F); excursions permitted to 15° to 30°C (59° to 86°F) [see USP Controlled Room Temperature].
Protect from moisture.
Dispense in a tight, light-resistant container as defined in the USP using a child-resistant closure.
To report SUSPECTED ADVERSE REACTIONS, contact Greenstone LLC at 1-800-438-1985 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch
Peacpack, NJ 07977
Code No.: DRUGS/AP/19/1993
displayName: DESCRIPTION SECTION
FDA Article Code: 34089-3
Metoprolol tartrate USP is a selective beta
1-adrenoreceptor blocking agent, available as 25, 50 and 100 mg tablets for oral administration. Metoprolol tartrate is (±)-1-(isopropylamino)-3-[
dextro-tartrate salt. Its structural formula is:
Metoprolol tartrate USP is a white, practically odorless, crystalline powder with a molecular weight of 684.82. It is very soluble in water; freely soluble in methylene chloride, in chloroform, and in alcohol; slightly soluble in acetone; and insoluble in ether.
Each tablet for oral administration contains 25 mg, 50 mg or 100 mg of metoprolol tartrate.
The tablets contain the following inactive ingredients: microcrystalline cellulose, corn starch, sodium starch glycollate, colloidal silicon dioxide, sodium lauryl sulfate, talc, magnesium stearate, hypromellose, titanium dioxide, polyethylene glycol and polysorbate 80. In addition, 50 mg tablet contains D&C Red #30 Aluminium Lake and 100 mg tablet contains FD&C Blue #2 Aluminium Lake as coloring agents.
Principal Display Panel
displayName: PACKAGE LABEL.PRINCIPAL DISPLAY PANEL
FDA Article Code: 51945-4
Metoprolol Tartrate Tablets, USP 25mg