Acetaminopheninteractions

Table 2 includes clinically significant interactions with tramadol hydrochloride and acetaminophen.

Table 2: Clinically Significant Drug Interactions with Tramadol Hydrochloride and Acetaminophen Inhibitors of CYP2D6 Clinical Impact: The concomitant use of tramadol hydrochloride and acetaminophen and CYP2D6 inhibitors may result in an increase in the plasma concentration of tramadol and a decrease in the plasma concentration of M1, particularly when an inhibitor is added after a stable dose of tramadol hydrochloride and acetaminophen is achieved. Since M1 is a more potent µ-opioid agonist, decreased M1 exposure could result in decreased therapeutic effects, and may result in signs and symptoms of opioid withdrawal in patients who had developed physical dependence to tramadol. Increased tramadol exposure can result in increased or prolonged therapeutic effects and increased risk for serious adverse events including seizures and serotonin syndrome. After stopping a CYP2D6 inhibitor, as the effects of the inhibitor decline, the tramadol plasma concentration will decrease and the M1 plasma concentration will increase which could increase or prolong therapeutic effects but also increase adverse reactions related to opioid toxicity, and may cause potentially fatal respiratory depression.

Intervention: If concomitant use of a CYP2D6 inhibitor is necessary, evaluate patients at frequent intervals for adverse reactions including opioid withdrawal, seizures and serotonin syndrome. If a CYP2D6 inhibitor is discontinued, consider lowering tramadol hydrochloride and acetaminophen dosage until stable drug effects are achieved. Evaluate patients at frequent intervals for adverse events including respiratory depression and sedation.

Examples: Quinidine, fluoxetine, paroxetine and bupropion Inhibitors of CYP3A4 Clinical Impact: The concomitant use of tramadol hydrochloride and acetaminophen and CYP3A4 inhibitors can increase the plasma concentration of tramadol and may result in a greater amount of metabolism via CYP2D6 and greater levels of M1. Follow patients closely for increased risk of serious adverse events including seizures and serotonin syndrome, and adverse reactions related to opioid toxicity including potentially fatal respiratory depression, particularly when an inhibitor is added after a stable dose of tramadol hydrochloride and acetaminophen is achieved. After stopping a CYP3A4 inhibitor, as the effects of the inhibitor decline, the tramadol plasma concentration will decrease, resulting in decreased opioid efficacy and possibly signs and symptoms of opioid withdrawal in patients who had developed physical dependence to tramadol.

Intervention: If concomitant use is necessary, consider dosage reduction of tramadol hydrochloride and acetaminophen until stable drug effects are achieved. Evaluate patients at frequent intervals for seizures and serotonin syndrome, and signs of respiratory depression and sedation at frequent intervals. If a CYP3A4 inhibitor is discontinued, consider increasing the tramadol hydrochloride and acetaminophen dosage until stable drug effects are achieved and evaluate patients for signs and symptoms of opioid withdrawal.

Examples: Macrolide antibiotics (e.g., erythromycin), azole-antifungal agents (e.g., ketoconazole), protease inhibitors (e.g., ritonavir) CYP3A4 Inducers Clinical Impact: The concomitant use of tramadol hydrochloride and acetaminophen and CYP3A4 inducers can decrease the plasma concentration of tramadol, resulting in decreased efficacy or onset of a withdrawal syndrome in patients who have developed physical dependence to tramadol. After stopping a CYP3A4 inducer, as the effects of the inducer decline, the tramadol plasma concentration will increase, which could increase or prolong both the therapeutic effects and adverse reactions, and may cause serious respiratory depression, seizures and serotonin syndrome.

Intervention: If concomitant use is necessary, consider increasing the tramadol hydrochloride and acetaminophen dosage until stable drug effects are achieved. Evaluate patients for signs of opioid withdrawal. If a CYP3A4 inducer is discontinued, consider tramadol hydrochloride and acetaminophen tablets dosage reduction and evaluate patients at frequent intervals for seizures and serotonin syndrome, and signs of respiratory depression and sedation. Patients taking carbamazepine, a CYP3A4 inducer, may have a significantly reduced analgesic effect of tramadol. Because carbamazepine increases tramadol metabolism and because of the seizure risk associated with tramadol, concomitant administration of tramadol hydrochloride and acetaminophen and carbamazepine is not recommended.

Examples: Rifampin, carbamazepine, phenytoin Benzodiazepines and Other Central Nervous System (CNS) Depressants Clinical Impact: Due to additive pharmacologic effect, the concomitant use of benzodiazepines or other CNS depressants, including alcohol, can increase the risk of hypotension, respiratory depression, profound sedation, coma, and death.

Intervention: Reserve concomitant prescribing of these drugs for use in patients for whom alternative treatment options are inadequate. Limit dosages and durations to the minimum required. Inform patients and caregivers of this potential interaction and educate them on the signs and symptoms of respiratory depression (including sedation). If concomitant use is warranted, consider prescribing naloxone for the emergency treatment of opioid overdose.

Examples: Benzodiazepines and other sedatives/hypnotics, anxiolytics, tranquilizers, muscle relaxants, general anesthetics, antipsychotics, other opioids, alcohol.

Serotonergic Drugs Clinical Impact: The concomitant use of opioids with other drugs that affect the serotonergic neurotransmitter system has resulted in serotonin syndrome.

Intervention: If concomitant use is warranted, frequently evaluate the patient, particularly during treatment initiation and dose adjustment. Discontinue tramadol hydrochloride and acetaminophen if serotonin syndrome is suspected.

Examples: Selective serotonin reuptake inhibitors (SSRIs), serotonin and norepinephrine reuptake inhibitors (SNRIs), tricyclic antidepressants (TCAs), triptans, 5-HT3 receptor antagonists, drugs that affect the serotonin neurotransmitter system (e.g., mirtazapine, trazodone, tramadol), certain muscle relaxants (i.e., cyclobenzaprine, metaxalone), monoamine oxidase (MAO) inhibitors (those intended to treat psychiatric disorders and also others, such as linezolid and intravenous methylene blue). Monoamine Oxidase Inhibitors (MAOIs) Clinical Impact: MAOI interactions with opioids may manifest as serotonin syndrome or opioid toxicity (e.g., respiratory depression, coma).

Intervention: Do not use tramadol hydrochloride and acetaminophen in patients taking MAOIs or within 14 days of stopping such treatment.

Examples: phenelzine, tranylcypromine, linezolid Mixed Agonist/Antagonist and Partial Agonist Opioid Analgesics Clinical Impact: May reduce the analgesic effect of tramadol hydrochloride and acetaminophen and/or precipitate withdrawal symptoms.

Intervention: Avoid concomitant use.

Examples: butorphanol, nalbuphine, pentazocine, buprenorphine Muscle Relaxants Clinical Impact: Tramadol may enhance the neuromuscular blocking action of skeletal muscle relaxants and produce an increased degree of respiratory depression.

Intervention: Because respiratory depression that may be greater than otherwise expected, decrease the dosage of tramadol hydrochloride and acetaminophen and/or the muscle relaxant as necessary. Due to the risk of respiratory depression with concomitant use of muscle relaxants and opioids, consider prescribing naloxone for the emergency treatment of opioid overdose.

Diuretics Clinical Impact: Opioids can reduce the efficacy of diuretics by inducing the release of antidiuretic hormone.

Intervention: Evaluate patients for signs of diminished diuresis and/or effects on blood pressure and increase the dosage of the diuretic as needed.

Anticholinergic Drugs Clinical Impact: The concomitant use of anticholinergic drugs may increase risk of urinary retention and/or severe constipation, which may lead to paralytic ileus.

Intervention: Evaluate patients for signs of urinary retention or reduced gastric motility when tramadol hydrochloride and acetaminophen is used concomitantly with anticholinergic drugs.

Digoxin Clinical Impact: Postmarketing surveillance of tramadol has revealed rare reports of digoxin toxicity.

Intervention: Evaluate patients at frequent intervals for signs of digoxin toxicity and adjust dosage of digoxin as needed.

Warfarin Clinical Impact: Postmarketing surveillance of tramadol has revealed rare reports of alteration of warfarin effect, including elevation of prothrombin times.

Intervention: Frequently reevaluate the prothrombin time of patients on warfarin for signs of an interaction and adjust the dosage of warfarin as needed. Mixed Agonist/Antagonist and Partial Agonist Opioid Analgesics: Avoid use with tramadol hydrochloride and acetaminophen because they may reduce analgesic effect of tramadol hydrochloride and acetaminophen or precipitate withdrawal symptoms.