cg/mL at 4 hours and 37.5 mcg/mL at 12 hours. If serum level is above the lower line, administer the entire course of NAC treatment. Withhold NAC therapy if the acetaminophen level is below the lower line.
Gastric decontamination with activated charcoal should be administered just prior to N-acetylcysteine (NAC) to decrease systemic absorption if acetaminophen ingestion is known or suspected to have occurred within a few hours of presentation. Serum acetaminophen levels should be obtained immediately if the patient presents 4 hours or more after ingestion to assess potential risk of hepatotoxicity; acetaminophen levels drawn less than 4 hours post-ingestion may be misleading. To obtain the best possible outcome, NAC should be administered as soon as possible where impending or evolving liver injury is suspected. Intravenous NAC may be administered when circumstances preclude oral administration.
Vigorous supportive therapy is required in severe intoxication. Procedures to limit the continuing absorption of the drug must be readily performed since the hepatic injury is dose-dependent and occurs early in the course of intoxication.
11 DESCRIPTION
Tramadol hydrochloride and acetaminophen tablets USP combine two analgesics, tramadol hydrochloride and opioid agonist, and acetaminophen.
The chemical name for tramadol hydrochloride is (±)cis-2-[(dimethylamino)methyl]-1-(3-methoxyphenyl) cyclohexanol hydrochloride. Its structural formula is:
Structure1
The molecular weight of tramadol hydrochloride is 299.84. Tramadol hydrochloride USP is a white, crystalline powder.
The chemical name for acetaminophen is N-acetyl-p-aminophenol. Its structural formula is:
Sturcture2
The molecular weight of acetaminophen is 151.17. Acetaminophen USP is an analgesic and antipyretic agent which occurs as a white, odorless, crystalline powder, possessing a slightly bitter taste.
Tramadol hydrochloride and acetaminophen tablets USP contain 37.5 mg of tramadol hydrochloride USP and 325 mg acetaminophen USP and are light yellow in color. Inactive ingredients in the tablet are corn starch, hypromellose, magnesium stearate, microcrystalline cellulose, polyethylene glycol, polysorbate 80, pregelatinized starch (maize), sodium starch glycolate (potato), titanium dioxide and yellow iron oxide.
Meets USP Dissolution Test 2.
12 CLINICAL PHARMACOLOGY
The following information is based on studies of tramadol alone or acetaminophen alone, except where otherwise noted:
12.1 Mechanism of Action
Tramadol hydrochloride and acetaminophen tablets contain tramadol, an opioid agonist and inhibitor of norepinephrine and serotonin re-uptake, and acetaminophen. Although the mode of action of tramadol is not completely understood, the analgesic effect of tramadol is believed to be due to both binding to µ-opioid receptors and weak inhibition of reuptake of norepinephrine and serotonin.
Opioid activity of tramadol is due to both low affinity binding of the parent compound and higher affinity binding of the O-demethylated metabolite M1 to µ-opioid receptors. In animal models, M1 is up to 6 times more potent than tramadol in producing analgesia and 200 times more potent in µ-opioid binding. Tramadol-induced analgesia is only partially antagonized by the opiate antagonist naloxone in several animal tests. The relative contribution of both tramadol and M1 to human analgesia is dependent upon the pla |
