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Mechanism Of Action
Indomethacin is a potent inhibitor of prostaglandin synthesis in vitro. Indomethacin concentrations are reached during therapy which have been demonstrated to produce in vivo effects. Prostaglandins sensitize afferent nerves and potentiate the action of bradykinin in inducing pain in animal models. Prostaglandins are mediators of inflammation. Since indomethacin is an inhibitor of prostaglandin synthesis, its mode of action may be due to a decrease of prostaglandins in peripheral tissues.
The relative bioavailability of TIVORBEX 40 mg capsules was compared to indomethacin immediate-release (IR) capsules 50 mg in 38 healthy subjects under fasted conditions in a single-dose crossover study.
TIVORBEX (indomethacin) 40 mg capsules do not result in an equivalent systemic exposure to 50 mg indomethacin IR capsules.
When taken under fasted conditions, a 20% lower dose of indomethacin in TIVORBEX 40 mg capsules resulted in a 21% lower mean systemic exposure (AUCinf) and an equivalent mean peak concentration (Cmax) compared to 50 mg indomethacin IR capsules. The median time to reach peak concentrations (Tmax) was 1.67 hours and 2.02 hours for TIVORBEX capsules and Indomethacin IR capsules, respectively.
Similar to indomethacin IR capsules, following single oral doses of TIVORBEX capsules 20 mg or 40 mg, indomethacin is readily absorbed. TIVORBEX Capsules attained peak plasma concentrations of approximately 1.2 and 2.4 mcg/mL, respectively, at 1.67 hours. Indomethacin is virtually 100% bioavailable, with 90% of the dose absorbed within 4 hours following dosing.
Administration of TIVORBEX Capsules 20 mg and 40 mg was associated with dose proportional pharmacokinetics.
Taking TIVORBEX with food causes a significant decrease in the rate but not the overall extent of systemic absorption of indomethacin compared to taking TIVORBEX on an empty stomach. TIVORBEX capsules results in 46% lower Cmax, 9% lower AUCinf, and 1.33 hours delayed Tmax (1.67 hours during fasted versus 3.00 hours during fed) under the fed condition compared to the fasted condition. Based on the food effect evaluation on the indomethacin IR capsules, the effect of food on indomethacin pharmacokinetics is comparable between TIVORBEX capsules and indomethacin IR capsules.
Indomethacin is highly bound to protein in plasma (about 99%) over the expected range of therapeutic plasma concentrations. Indomethacin crosses the blood-brain barrier and the placenta, and appears in breast milk.
Indomethacin exists in the plasma as the parent drug and its desmethyl, desbenzoyl, and desmethyldesbenzoyl metabolites, all in the unconjugated form. Appreciable formation of glucuronide conjugates of each metabolite and of indomethacin are formed.
Indomethacin is eliminated via metabolism and subsequent renal and biliary excretion. Indomethacin undergoes appreciable enterohepatic circulation. About 60% of an oral dose is recovered in urine as drug and metabolites (26% as indomethacin and its glucuronide), and 33% is recovered in feces (1.5% as indomethacin). The mean half-life of indomethacin from TIVORBEX capsules 40 mg is 7.6 hours and is comparable to indomethacin IR capsules 50 mg (7.2 hours).
Pediatric: The pharmacokinetics of TIVORBEX has not been investigated in pediatric patients.
Race: Pharmacokinetic differences due to race have not been identified.
Hepatic Impairment: The pharmacokinetics of TIVORBEX has not been investigated in patients with hepatic impairment.
Renal Impairment: The pharmacokinetics of TIVORBEX has not been investigated in patients with renal impairment [see WARNINGS AND PRECAUTIONS].
The efficacy of TIVORBEX for the treatment of acute pain was demonstrated in two multicenter, randomized, double-blind, placebo-controlled, parallel arm studies comparing TIVORBEX 20 mg three times daily, 40 mg twice daily, 40 mg three times daily, and placebo in patients with pain following bunionectomy (Study 1 and Study 2). The two studies enrolled a total of 835 patients with a mean age of 40 years (range 18 to 68 years) a minimal pain intensity rating of at least 40 mm on a 100-mm visual analog scale (VAS) during the 9-hour period after discontinuation of the anesthetic block following bunionectomy surgery. Patients were randomized equally across the treatment groups.
The mean pain intensity measured by VAS at baseline for all treatment groups in both studies ranged from 71 to 74 mm. One tablet of hydrocodone/acetaminophen 10 mg/325 mg was permitted every 4 to 6 hours as rescue medication. There was a greater use of concomitant opioid rescue medication in placebo-treated patients than in TIVORBEX-treated patients. In Study 1, 89% of patients in the TIVORBEX 20 mg three times daily group, 90% of the patients in the TIVORBEX 40 mg twice daily group, 82% in the TIVORBEX 40 mg three times daily group, and 97% of patients in the placebo group took rescue medication for pain management during the study. In Study 2, 87% of patients in the TIVORBEX 20 mg three times daily group, 76% of the patients in the TIVORBEX 40 mg twice daily group, 80% in the TIVORBEX 40 mg three times daily group, and 89% of patients in the placebo group took rescue medication for pain management during the study.
The average pain intensities over time are depicted for the treatment groups in Figure 1 for Study 1 and Figure 2 for Study 2. In both studies, TIVORBEX Capsules 20 mg three times daily, 40 mg twice daily and 40 mg three times daily, demonstrated efficacy in pain intensity reduction compared with placebo, as measured by the sum of pain intensity difference over 0 to 48 hours after the first dose.
Figure 1 : Average Pain Intensity Over 48 Hours for
TIVORBEX and Placebo Groups – Study 1
Figure 2 : Average Pain
Intensity Over 48 Hours for TIVORBEX and Placebo Groups – Study 2
Last reviewed on RxList: 3/5/2014
This monograph has been modified to include the generic and brand name in many instances.
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