Metaproterenol Syrup

WARNING/CAUTION: Even though it may be rare, some people may have very bad and sometimes deadly side effects when taking a drug. Tell your doctor or get medical help right away if you have any of the following signs or symptoms that may be related to a very bad side effect:

• Signs of an allergic reaction, like rash; hives; itching; red, swollen, blistered, or peeling skin with or without fever; wheezing; tightness in the chest or throat; trouble breathing or talking; unusual hoarseness; or swelling of the mouth, face, lips, tongue, or throat.
• Signs of high blood pressure like very bad headache or dizziness, passing out, or change in eyesight.
• A fast heartbeat.
• A heartbeat that does not feel normal.
• Shakiness.

All drugs may cause side effects. However, many people have no side effects or only have minor side effects. Call your doctor or get medical help if any of these side effects or any other side effects bother you or do not go away:

• Feeling nervous and excitable.
• Headache.

These are not all of the side effects that may occur. If you have questions about side effects, call your doctor. Call your doctor for medical advice about side effects.

You may report side effects to the FDA at 1-800-FDA-1088. You may also report side effects at http://www.fda.gov/medwatch.

Metaproterenol sulfate syrup is an oral bronchodilator.

Each teaspoonful (5 mL), for oral administration, contains metaproterenol sulfate 10 mg. In addition, each teaspoonful (5 mL) contains the following inactive ingredients:

citric acid, edetate disodium, FD&C Red No. 40, glycerin, hydroxyethyl cellulose, black cherry flavor, propylene glycol, saccharin sodium, sodium benzoate, sorbitol solution, sodium citrate and purified water.

Metaproterenol sulfate, 1- (3, 5 dihydroxyphenyl) -2-isopropyl - aminoethanol sulfate, is a white, crystalline, racemic mixture of two optically active isomers. It has the following structural formula:

In vitro studies and in vivo pharmacologic studies have demonstrated that metaproterenol sulfate has a preferential effect on beta2 adrenergic receptors compared with isoproterenol. While it is recognized that beta2 adrenergic receptors are the predominant receptors in bronchial smooth muscle, recent data indicate that there is a population of beta2 receptors in the human heart existing in a concentration between 10 to 50%. The precise function of these, however, is not yet established (see WARNINGS section).

The pharmacologic effects of beta adrenergic agonist drugs, including metaproterenol, are at least in part attributable to stimulation through beta adrenergic receptors of intracellular adenyl cyclase, the enzyme which catalyzes the conversion of adenosine triphosphate (ATP) to cyclic-3’, 5’ -adenosine monophosphate (c-AMP). Increased c-AMP levels are associated with relaxation of bronchial smooth muscle and inhibition of release of mediators of immediate hypersensitivity from cells, especially from mast cells.

PHARMACOKINETICS: Absorption, biotransformation and excretion studies in humans following oral administration have indicated that an average of less than 10% of the drug is absorbed intact; it is not metabolized by catechol-0-methyltransferase nor converted to glucuronide conjugates but is excreted primarily as the sulfate conjugate formed in the gut.

Pulmonary function tests performed after the administration of metaproterenol usually show improvement, e.g., an increase in the one-second forced expiratory volume (FEV1), maximum expiratory flow rate, peak expiratory flow rate, forced vital capacity, and/or a decrease in airway resistance. The resultant decrease in airway obstruction may relieve the dyspnea associated with bronchospasm.

Pulmonary function has been monitored in controlled single- and multiple-dose studies. The duration of effect of a single dose of metaproterenol sulfate syrup (that is, the period of time during which there is a 15% or greater increase in mean FEV1) was up to 4 hours. Recent studies in laboratory animals (minipigs, rodents and dogs) recorded the occurrence of cardiac arrhythmias and sudden death (with histologic evidence of myocardial necrosis) when beta agonists and methylxanthines were administered concurrently. The significance of these findings when applied to humans is currently unknown.

The expected symptoms with overdosage are those of excessive beta stimulation and/or any of the symptoms listed under ADVERSE REACTIONS, e.g., angina, hypertension or hypotension. arrhythmias, nervousness, headache, tremor, dry mouth, palpitation, nausea, dizziness, fatigue, malaise and insomnia.

The treatment consists of discontinuation of metaproterenol together with appropriate symptomatic therapy.

Metaproterenol Sulfate Syrup, USP is available as a red, cherry-flavored syrup containing 10 mg of metaproterenol sulfate per teaspoonful (5 mL) in 473 mL (one pint) bottles.

Store below 86°F (30°C). Protect from light.

Manufactured by:

Silarx Pharmaceuticals, Inc.
1033 Stoneleigh Ave
Carmel, NY 10512