ULTRACET

ULTRACET- tramadol hydrochloride and acetaminophen tablet, coated
A-S Medication Solutions LLC

HEPATOTOXICITY

ULTRACET® contains tramadol HCl and acetaminophen. Acetaminophen has been associated with cases of acute liver failure, at times resulting in liver transplant and death. Most of the cases of liver injury are associated with the use of acetaminophen at doses that exceed 4,000 milligrams per day, and often involve more than one acetaminophen-containing product (see WARNINGS).

DESCRIPTION

ULTRACET® (tramadol hydrochloride/acetaminophen) Tablets combines two analgesics, tramadol 37.5 mg and acetaminophen 325 mg.

The chemical name for tramadol hydrochloride is (±)cis -2-[(dimethylamino)methyl]-1-(3-methoxyphenyl) cyclohexanol hydrochloride. Its structural formula is:

Chemical Structure

The molecular weight of tramadol hydrochloride is 299.84. Tramadol hydrochloride is a white, bitter, crystalline, and odorless powder.

The chemical name for acetaminophen is N -acetyl-p -aminophenol. Its structural formula is:

Chemical Structure

The molecular weight of acetaminophen is 151.17. Acetaminophen is an analgesic and antipyretic agent which occurs as a white, odorless, crystalline powder, possessing a slightly bitter taste.

ULTRACET® tablets contain 37.5 mg tramadol hydrochloride and 325 mg acetaminophen and are light yellow in color. Inactive ingredients in the tablet are powdered cellulose, pregelatinized corn starch, sodium starch glycolate, corn starch, magnesium stearate, hypromellose, polyethylene glycol, polysorbate 80, titanium dioxide, iron oxide, and carnauba wax.

Meets USP Dissolution Test 2

CLINICAL PHARMACOLOGY

The following information is based on studies of tramadol alone or acetaminophen alone, except where otherwise noted:

Pharmacodynamics

ULTRACET® contains tramadol and acetaminophen. Tramadol is a centrally acting synthetic opioid analgesic. Although its mode of action is not completely understood, from animal tests, at least two complementary mechanisms appear applicable: binding of parent and M1 metabolite to µ-opioid receptors and weak inhibition of reuptake of norepinephrine and serotonin.

Opioid activity 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 plasma concentrations of each compound (see CLINICAL PHARMACOLOGY, Pharmacokinetics).

Tramadol has been shown to inhibit reuptake of norepinephrine and serotonin in vitro, as have some other opioid analgesics. These mechanisms may contribute independently to the overall analgesic profile of tramadol.

Apart from analgesia, tramadol administration may produce a constellation of symptoms (including dizziness, somnolence, nausea, constipation, sweating, and pruritus) similar to that of other opioids.

Acetaminophen is a non-opiate, non-salicylate analgesic.

Pharmacokinetics

Tramadol is administered as a racemate and both the [-] and [+] forms of both tramadol and M1 are detected in the circulation. The pharmacokinetics of plasma tramadol and acetaminophen following oral administration of one ULTRACET® tablet are shown in Table 1. Tramadol has a slower absorption and longer half-life when compared to acetaminophen.

Table 1: Summary of Mean (±SD) Pharmacokinetic Parameters of the (+)- and (-) Enantiomers of Tramadol and M1 and Acetaminophen Following A Single Oral Dose Of One Tramadol/Acetaminophen Combination Tablet (37.5 mg/325 mg) in Volunteers
Parameter * (+)-Tramadol (-)-Tramadol (+)-M1 (-)-M1 acetaminophen
*
For acetaminophen, Cmax was measured as µg/mL.
Cmax (ng/mL) 64.3 (9.3) 55.5 (8.1) 10.9 (5.7) 12.8 (4.2) 4.2 (0.8)
tmax (h) 1.8 (0.6) 1.8 (0.7) 2.1 (0.7) 2.2 (0.7) 0.9 (0.7)
CL/F (mL/min) 588 (226) 736 (244) - - - - 365 (84)
t1/2 (h) 5.1 (1.4) 4.7 (1.2) 7.8 (3.0) 6.2 (1.6) 2.5 (0.6)

A single-dose pharmacokinetic study of ULTRACET® in volunteers showed no drug interactions between tramadol and acetaminophen. Upon multiple oral dosing to steady state, however, the bioavailability of tramadol and metabolite M1 was lower for the combination tablets compared to tramadol administered alone. The decrease in AUC was 14% for (+)-tramadol, 10.4% for (-)-tramadol, 11.9% for (+)-M1, and 24.2% for (-)-M1. The cause of this reduced bioavailability is not clear. Following single- or multiple-dose administration of ULTRACET® , no significant change in acetaminophen pharmacokinetics was observed when compared to acetaminophen given alone.

Absorption

The absolute bioavailability of tramadol from ULTRACET® tablets has not been determined. Tramadol hydrochloride has a mean absolute bioavailability of approximately 75% following administration of a single 100 mg oral dose of ULTRAM® tablets. The mean peak plasma concentration of racemic tramadol and M1 after administration of two ULTRACET® tablets occurs at approximately two and three hours, respectively, post-dose.

Peak plasma concentrations of acetaminophen occur within one hour and are not affected by co-administration with tramadol. Oral absorption of acetaminophen following administration of ULTRACET® occurs primarily in the small intestine.

Food Effects

When ULTRACET® was administered with food, the time to peak plasma concentration was delayed for approximately 35 minutes for tramadol and almost one hour for acetaminophen. However, peak plasma concentrations, and the extents of absorption, of tramadol and acetaminophen were not affected. The clinical significance of this difference is unknown.

Distribution

The volume of distribution of tramadol was 2.6 and 2.9 L/kg in male and female subjects, respectively, following a 100 mg intravenous dose. The binding of tramadol to human plasma proteins is approximately 20% and binding also appears to be independent of concentration up to 10 µg/mL. Saturation of plasma protein binding occurs only at concentrations outside the clinically relevant range.

Acetaminophen appears to be widely distributed throughout most body tissues except fat. Its apparent volume of distribution is about 0.9 L/kg. A relative small portion (~20%) of acetaminophen is bound to plasma protein.

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