Prednisone Acetate – Chlorpheniramine Maleate – Ascorbic Acid
Glucocorticoid – Antihistamine
Action And Clinical Pharmacology: Metreton combines the anti-inflammatory and antiallergic effects of the corticosteroid prednisone with the antihistaminic activity of chlorpheniramine. In addition, Metreton tablets contain ascorbic acid.
By using prednisone and chlorpheniramine in combination, comparable results usually are obtained with smaller amounts of corticosteroid than when the corticosteroid is given alone.
Indications And Clinical Uses: For the relief of hay fever, allergic rhinitis, intractable asthma and other allergic states.
Contra-Indications: Systemic fungal infections; hypersensitivity to prednisone, to other corticosteroids or to any component of Metreton.
Precautions: Prednisone: Dosage adjustments may be required with remission or exacerbation of the disease process, the patient’s individual response to therapy and exposure of the patient to emotional or physical stress such as serious infection, surgery or injury. Monitoring may be necessary for up to 1 year following cessation of long-term or high-dose corticosteroid therapy. Drug induced secondary adrenocortical insufficiency may be minimized by gradual dosage reduction. This type of relative insufficiency may persist for months after discontinuation of therapy, therefore, in any stress situation occurring during that period, reinstitute hormone therapy. If the patient is receiving steroids already, the dosage may have to be increased.
The lowest possible dose of corticosteroid should be used to control the condition under treatment. A gradual dosage reduction is recommended.
Corticosteroid effect is enhanced in patients with hypothyroidism or in those with cirrhosis.
Cautious use of corticosteroids is advised in patients with ocular herpes simplex because of possible corneal perforation.
Psychic derangements may appear with corticosteroid therapy. Existing emotional instability or psychotic tendencies may be aggravated by corticosteroids.
Corticosteroids should be used with caution in: nonspecific ulcerative colitis, if there is a probability of impending perforation, abscess, or other pyogenic infection; diverticulitis; fresh intestinal anastomoses; active or latent peptic ulcer; renal insufficiency; hypertension; osteoporosis; and myasthenia gravis.
Since complications of glucocorticoid treatment are dependent on dosage and duration of treatment, a risk/benefit decision must be made with each patient.
Corticosteroids may mask some signs of infection, and new infections may appear during use. When corticosteroids are used, decreased resistance and inability to localize infection may occur.
Prolonged corticosteroid use may produce posterior subcapsular cataracts (especially in children), glaucoma with possible damage to the optic nerves, and may enhance secondary ocular infections due to fungi or viruses.
Corticosteroid therapy may cause hyperacidity or peptic ulcer. Since the appearance of a peptic ulcer may be asymptomatic until perforation or hemorrhage occurs, take x-rays when treatment is prolonged or when there is gastric distress. An ulcer regimen, including an antacid, should be considered as a prophylactic measure during prolonged therapy.
Average and large doses of corticosteroids can cause elevation of blood pressure, salt and water retention, and increased excretion of potassium. These effects are less likely to occur with the synthetic derivatives except when used in large doses. Dietary salt restriction and potassium supplementation may be considered. All corticosteroids increase calcium excretion. Since mineralocorticoid secretion may be impaired, salt and/or a mineralocorticoid should be administered concurrently.
While on corticosteroid therapy patients should not be vaccinated against smallpox. Conversely, patients with vacinia should not receive corticosteroid therapy. Other immunization procedures should not be undertaken in patients receiving corticosteroids, especially high doses, because of possible hazards of neurological complications and lack of antibody response.
Patients who are on immunosuppressant doses of corticosteroids should be warned to avoid exposure to chickenpox or measles, and if exposed, to obtain medical advice. This is of particular importance in children.
Corticosteroid therapy in active tuberculosis should be restricted to those cases of fulminating or disseminated tuberculosis in which the corticosteroid is used in conjunction with an appropriate antituberculous regimen.
If corticosteroids are indicated in patients with latent tuberculosis, close observation is necessary since reactivation of the disease may occur. During prolonged corticosteroid therapy, patients should receive chemoprophylaxis.
Growth and development of children on prolonged corticosteroid therapy should be followed carefully, since corticosteroid administration can disturb growth rates and inhibit endogenous corticosteroid production in these patients.
Corticosteroid therapy may alter the motility and number of spermatozoa in some patients.
Pregnancy and Lactation: Since adequate human reproduction studies have not been done with corticosteroids, the use of these drugs in pregnancy, nursing mothers or women of child bearing potential requires that the possible benefits of the drug be weighed against the potential hazards to the mother and fetus or infant. Infants born of mothers who have received substantial doses of corticosteroids during pregnancy should be carefully observed for signs of hypoadrenalism.
Advise patients to inform subsequent physicians of the prior use of corticosteroids.
Chlorpheniramine Maleate: Metreton should be used with caution in patients with narrow angle glaucoma, stenosing peptic ulcer, pyloroduodenal obstruction, prostatic hypertrophy or bladder neck obstruction, cardiovascular disease including hypertension, in those with increased intraocular pressure or hyperthyroidism.
Occupational Hazards: Patients should be warned about engaging in activities requiring mental alertness, such as driving a car or operating appliances, machinery, etc.
Conventional antihistamines may cause dizziness, sedation, and hypotension in patients over 60 years of age.
Children: Safety and effectiveness have not been established in children under 2 years of age.
Drug Interactions: Concurrent use of phenobarbital, phenytoin, rifampin or ephedrine may enhance the rate of metabolism and clearance of corticosteroids, thereby reducing their therapeutic effects. May inhibit the response to somatotropin.
Patients receiving both a corticosteroid and an estrogen should be observed for excessive corticosteroid effects.
Concurrent use of corticosteroids with potassium-depleting diuretics may enhance hypokalemia. Concurrent use of corticosteroids with cardiac glycosides may enhance the possibility of arrhythmias or digitalis toxicity associated with hypokalemia. Corticosteroids may enhance the potassium depletion caused by amphotericin B. In all patients taking any of these drug therapy combinations, serum electrolyte determinations, particularly potassium levels, should be monitored closely.
Concurrent use of corticosteroids with coumarin-type anticoagulants may increase or decrease the anticoagulant effect, possibly requiring adjustment in dosage.
Combined effects of noncorticosteroid drugs or alcohol with glucocorticoids may result in an increased occurrence or increased severity of gastrointestinal ulceration.
Corticosteroids may decrease blood salicylate concentrations. ASA should be used cautiously in conjunction with corticosteroids in hypoprothrombinemia.
Corticosteroids may affect the nitroblue tetrazolium test for bacterial infection and produce false negative results.
Dose adjustments of an antidiabetic drug may be necessary when corticosteroids are given to diabetics.
MAO inhibitors prolong and intensify the effects of antihistamines; severe hypotension may occur. Concomitant use of antihistamines with alcohol, tricyclic antidepressants, barbiturates or other CNS depressants may potentiate the sedative effect of chlorpheniramine maleate. Antihistamines may inhibit the action of oral anticoagulants.
Adverse Reactions: The physician should be alerted to the possibility of any adverse effects associated with the use of corticosteroids and antihistamines, especially of the sedating type.
Prednisone: Adverse reactions to this component are the same as those reported with other corticosteroids and they are related to dose and duration of therapy.
Adverse reactions reported for corticosteroids include: Fluid and Electrolyte Disturbances: sodium retention, potassium loss, hypokalemic alkalosis; fluid retention, congestive heart failure in susceptible patients; hypertension.
Musculoskeletal: muscle weakness, corticosteroid myopathy, loss of muscle mass; aggravation of myasthenic symptoms in myasthenia gravis; osteoporosis; vertebral compression fractures; aseptic necrosis of femoral and humeral heads; pathologic fracture of long bones; tendon rupture.
Gastrointestinal: peptic ulcer with possible subsequent perforation and hemorrhage; pancreatitis, abdominal distention; ulcerative esophagitis.
Dermatologic: impaired wound healing, skin atrophy, thin fragile skin; petechiae and ecchymoses; facial erythema; increased sweating; suppressed reactions to skin tests; reactions such as allergic dermatitis, urticaria, angioneurotic edema.
Neurologic: convulsions; increased intracranial pressure with papilledema (pseudotumor cerebri) usually after treatment; vertigo; headache.
Endocrine: menstrual irregularities; development of cushingoid state; suppression of fetal intrauterine or childhood growth; secondary adrenocortical and pituitary unresponsiveness, particularly in times of stress, as in trauma, surgery or illness; decreased carbohydrate tolerance, manifestations of latent diabetes mellitus, increased requirements of insulin or oral hypoglycemic agents in diabetics.
Ophthalmic: posterior subcapsular cataracts; increased intraocular pressure, glaucoma; exophthalmos.
Metabolic: negative nitrogen balance due to protein catabolism.
Psychiatric: euphoria, mood swings; severe depression to frank psychotic manifestations; personality changes; hyperirritability; insomnia.
Other: anaphylactoid or hypersensitivity and hypotensive or shock-like reactions.
Chlorpheniramine Maleate: Adverse reactions to this component have been the same as those reported with other conventional (sedating) antihistamines, and rarely cause toxicity. Slight to moderate drowsiness is the most frequent side effect of chlorpheniramine maleate. Adverse effects of sedating antihistamines vary in incidence and severity. Among these are cardiovascular, hematologic (pancytopenia, thrombocytopenia, hemolytic anemia), neurologic (confusion, hallucinations, tremor), gastrointestinal (urinary retention), respiratory adverse reactions and mood changes. The most common effects include sedation, sleepiness, dizziness, disturbed coordination, epigastric distress, rash, dry mouth and thickening of bronchial secretions.
Symptoms And Treatment Of Overdose: Symptoms: Metreton is a combination product and, therefore, the potential toxicity of each of its components must be considered. Toxicity from a single excessive dose of Metreton results primarily from the chlorpheniramine maleate component.
A single excessive dose of a corticosteroid should not be expected to produce acute symptoms. Except at the most extreme dosages, a few days of excessive glucocorticosteroid dosing is unlikely to produce harmful results in the absence of specific contraindications, such as in patients at particular risk due to underlying conditions or on concomitant medications likely to interact adversely with the prednisone component.
Overdosage reactions with conventional (sedating) antihistamines may vary from CNS depression (sedation, apnea, diminished mental alertness, cardiovascular collapse) to stimulation (insomnia, hallucinations, tremor, convulsions) to death. Other signs and symptoms may include dizziness, tinnitus, ataxia, blurred vision and hypotension. In children, stimulation is dominant, as are atropine-like signs and symptoms (dry mouth, fixed, dilated pupils, flushing, fever, and gastrointestinal symptoms). Hallucinations, incoordination, and convulsions of the tonic-clonic type may occur. In adults, a cycle consisting of depression with drowsiness and coma, and an excitement phase leading to convulsions followed by depression may occur.
Treatment: Acute overdosage should be treated immediately by inducing emesis or by the administration of gastric lavage. Dialysis has not been found helpful. Treatment of the signs and symptoms is symptomatic and supportive. Stimulants should not be used. Vasopressors may be used to treat hypotension. Convulsions are best treated with short-acting depressants, such as thiopental. Maintain adequate fluid intake and monitor electrolytes in serum and urine, with particular attention to sodium and potassium balance. Treat electrolyte imbalance if necessary.
Dosage And Administration: Average initial dosage will be 1 or 2 tablets after meals and at bedtime and is not to exceed 8 tablets daily. After 2 weeks of therapy, patients should be re-evaluated to determine whether Metreton dosage can be reduced. As improvement occurs, the dosage should be reduced gradually to the minimum maintenance level and discontinued where possible.
When symptoms of respiratory allergies are adequately controlled, slow withdrawal of the combination product and treatment with an antihistamine alone should be considered.
Availability And Storage: Each white tablet contains: prednisone acetate USP 2.5 mg, chlorpheniramine maleate USP 2 mg and ascorbic acid USP 75 mg. Nonmedicinal ingredients: cornstarch, lactose, magnesium stearate, povidone. Tartrazine-free. Bottles of 100.
METRETON® Schering Prednisone Acetate – Chlorpheniramine Maleate – Ascorbic Acid Glucocorticoid – Antihistamine