The precise mechanism of action of hydrocodone and other opiates is not known, although it is believed to relate to the existence of opiate receptors in the central nervous system. In addition to analgesia, narcotics may produce drowsiness, changes in mood and mental clouding. The analgesic action of acetaminophen involves peripheral influences, but the specific mechanism is as yet undetermined.
Antipyretic activity is mediated through hypothalamic heat regulating centers. Acetaminophen inhibits prostaglandin synthetase. Therapeutic doses of acetaminophen have negligible effects on the cardiovascular or respiratory systems; however, toxic doses may cause circulatory failure and rapid, shallow breathing.
Pharmacokinetics The behavior of the individual components is described below: Hydrocodone: Following a 10 mg oral dose of hydrocodone administered to five adult male subjects, the mean peak concentration was Maximum serum levels were achieved at 1.
Hydrocodone exhibits a complex pattern of metabolism including O-demethylation, Ndemethylation and 6-keto reduction to the corresponding 6-a- and 6-b-hydroxy-metabolites. Acetaminophen: Acetaminophen is rapidly absorbed from the gastrointestinal tract and is distributed throughout most body tissues.
The plasma half-life is 1. Elimination of acetaminophen is principally by liver metabolism conjugation and subsequent renal excretion of metabolites. Patients known to be hypersensitive to other opioids may exhibit cross-sensitivity to hydrocodone. WARNINGS Respiratory Depression: At high doses or in sensitive patients, hydrocodone may produce dose-related respiratory depression by acting directly on the brain stem respiratory center.
Hydrocodone also affects the center that controls respiratory rhythm, and may produce irregular and periodic breathing. Head Injury and Increased Intracranial Pressure: The respiratory depressant effects of narcotics and their capacity to elevate cerebrospinal fluid pressure may be markedly exaggerated in the presence of head injury, other intracranial lesions or a preexisting increase in intracranial pressure.
Furthermore, narcotics produce adverse reactions which may obscure the clinical course of patients with head injuries. Acute Abdominal Conditions: The administration of narcotics may obscure the diagnosis or clinical course of patients with acute abdominal conditions. The usual precautions should be observed and the possibility of respiratory depression should be kept in mind. Cough Reflex: Hydrocodone suppresses the cough reflex; as with all narcotics, caution should be exercised when hydrocodone bitartrate and acetaminophen tablets are used postoperatively and in patients with pulmonary disease.
Alcohol and other CNS depressants may produce an additive CNS depression, when taken with this combination product, and should be avoided. Hydrocodone may be habit-forming. Patients should take the drug only for as long as it is prescribed, in the amounts prescribed, and no more frequently than prescribed.
Drug Interactions Patients receiving other narcotic analgesics, antihistamines, antipsychotics, antianxiety agents, or other CNS depressants including alcohol concomitantly with hydrocodone bitartrate and acetaminophen tablets may exhibit an additive CNS depression. When combined therapy is contemplated, the dose of one or both agents should be reduced.
The use of MAO inhibitors or tricyclic antidepressants with hydrocodone preparations may increase the effect of either the antidepressant or hydrocodone. Drug and Laboratory Test Interactions Acetaminophen may produce false-positive test results for urinary 5-hydroxyindoleacetic acid.
Carcinogenesis, Mutagenesis, Impairment of Fertility No adequate studies have been conducted in animals to determine whether hydrocodone or acetaminophen have a potential for carcinogenesis, mutagenesis, or impairment of fertility. Pregnancy Category C: There are no adequate and well-controlled studies in pregnant women. Hydrocodone bitartrate and acetaminophen tablets should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus.
Nonteratogenic Effects: Babies born to mothers who have been taking opioids regularly prior to delivery will be physically dependent. The withdrawal signs include irritability and excessive crying, tremors, hyperactive reflexes, increased respiratory rate, increased stools, sneezing, yawning, vomiting, and fever.
The intensity of the syndrome does not always correlate with the duration of maternal opioid use or dose. There is no consensus on the best method of managing withdrawal. Labor and Delivery As with all narcotics, administration of hydrocodone bitartrate and acetaminophen tablets to the mother shortly before delivery may result in some degree of respiratory depression in the newborn, especially if higher doses are used.
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