WARNINGS
Methadone Hydrochloride Tablets, USP are for oral administration only and must not be used for injection. It is required that Methadone Hydrochloride Tablets, USP, if dispensed, be packaged in child-resistant containers and kept out of the reach of children to prevent accidental ingestion.
Interaction With Other Central Nervous System Depressants — Methadone should be used with caution and in reduced dosage in patients who are concurrently receiving other narcotic analgesics, general anesthetics, phenothiazines, other tranquilizers, sedative-hypnotics, tricyclic antidepressants, and other CNS depressants (including alcohol). Respiratory depression, hypotension, and profound sedation or coma may result.
Anxiety — Since methadone, as used by tolerant subjects at a constant maintenance dosage, is not a tranquilizer, patients who are maintained on this drug will react to life problems and stresses with the same symptoms of anxiety as do other individuals. The physician should not confuse such symptoms with those of narcotic abstinence and should not attempt to treat anxiety by increasing the dosage of methadone. The action of methadone in maintenance treatment is limited to the control of narcotic symptoms and is ineffective for relief of general anxiety.
Head Injury and Increased Intracranial Pressure — The respiratory depressant effects of the methadone and its capacity to elevate cerebrospinal-fluid pressure may be markedly exaggerated in the presence of increased intracranial pressure. Furthermore, narcotics produce side effects that may obscure the clinical course of patients with head injuries. In such patients, methadone must be used with caution and only if it is deemed essential.
Asthma and Other Respiratory Conditions — Methadone should be used with caution in patients having an acute asthmatic attack, in those with chronic obstructive pulmonary disease or cor pulmonale, and in individuals with a substantially decreased respiratory reserve, preexisting respiratory depression, hypoxia, or hypercapnia. In such patients, even usual therapeutic doses of narcotics may decrease respiratory drive while simultaneously increasing airway resistance to the point of apnea.
Hypotensive Effect — The administration of methadone may result in severe hypotension in an individual whose ability to maintain normal blood pressure has already been compromised by a depleted blood volume or concurrent administration of such drugs as the phenothiazines or certain anesthetics.
Use in Ambulatory Patients — Methadone may impair the mental and/or physical abilities required for the performance of potentially hazardous tasks, such as driving a car or operating machinery. The patient should be cautioned accordingly.
Methadone, like other narcotics, may produce orthostatic hypotension in ambulatory patients.
Use in Pregnancy — Safe use in pregnancy has not been established in relation to possible adverse effects on fetal development. Therefore, methadone should not be used in pregnant women unless, in the judgment of the physician, the potential benefits outweigh the possible hazards.
Methadone is not recommended for obstetric analgesia because its long duration of action increases the probability of respiratory depression in the newborn.
Use in Children — Methadone is not recommended for use as an analgesic in children, since documented clinical experience has been insufficient to establish a suitable dosage regimen for the pediatric age group.
PRECAUTIONS
Drug Interactions:
Pentazocine — Patients who are addicted to heroin or who are on the methadone maintenance program may experience withdrawal symptoms when given an opioid agonist-antagonist, such as pentazocine.
Rifampin — The concurrent administration of rifampin may possibly reduce the blood concentration of methadone to a degree sufficient to produce withdrawal symptoms. The mechanism by which rifampin may decrease blood concentrations of methadone is not fully understood although enhanced microsomal drug-metabolized enzymes may influence drug disposition.
Monoamine Oxidase (MAO) Inhibitors — Therapeutic doses of meperidine have precipitated severe reactions in patients concurrently receiving monoamine oxidase inhibitors or those who have received such agents within 14 days. Similar reactions thus far have not been reported with methadone; but if the use of methadone is necessary in such patients, a sensitivity test should be performed in which repeated small incremental doses are administered over the course of several hours while the patient's condition and vital signs are under careful observation.
Desipramine — Blood levels of desipramine have increased with concurrent methadone therapy.
Special-Risk Patients — Methadone should be given with caution and the initial dose should be reduced in certain patients, such as the elderly or debilitated and those with severe impairment of hepatic or renal function, hypothyroidism, Addison's disease, prostatic hypertrophy, or urethral stricture.
Acute Abdominal Conditions — The administration of methadone or other narcotics may obscure the diagnosis or clinical course in patients with acute abdominal conditions.
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