Levels of structural organization in the human body

1PALEXIA® IR PRODUCT INFORMATION AUST R 165310, 165317, 165318NAME OF THE MEDICINEPALEXIA® IR 50 mg tapentadol (as hydrochloride) immediate release, film coatedtabletsPALEXIA® IR 75 mg tapentadol (as hydrochloride) immediate release, film coatedtabletsPALEXIA® IR 100 mg tapentadol (as hydrochloride) immediate release, film coated tabletsDESCRIPTIONPALEXIA® IR immediate release tablets contain tapentadol hydrochloride (HCl) which is a centrally acting synthetic analgesic combining mu-agonist and noradrenaline re-uptake inhibition activity in a single molecule. Tapentadol is a white to off-white powder; freely soluble in water and methanol, and soluble in ethanol. The pKa1 is 9.36and pKa2 is 10.37 determined in 0.15 M KCl solution. The partition coefficient is defined as the ratio of the equilibrium concentrations of a single neutral molecular species in a 1-octanol/aqueous buffered solution 2-phase system. The value of log P for tapentadol hydrochloride in 1-octanol/water is 2.89 ± 0.01. The chemical name for tapentadol HCl is 3-[(1R,2R)-3-(dimethylamino)-1-ethyl-2-methylpropyl]phenol monohydrochloride. The molecular weight of tapentadol HCl is 257.80, and the empirical formula is C14H23NO•HCl. The structural formula of tapentadol HCl (CAS number: 175591-09-0) is: PALEXIA® IR tablets contain 50, 75 or100 mg tapentadol (as hydrochloride). Excipients in the table core are: microcrystalline cellulose, lactose, croscamellose sodium, povidone (K30) and magnesium stearate. Excipients in the film coating are: polyvinyl alcohol, titanium dioxide (E171), macrogol 3350, talc, iron oxide yellow (E172) (75 and 100 mg tablets only), iron oxide red (E172) (75 and 100 mg tablets only), and iron oxide black (E172) (100 mg tablets only).PHARMACOLOGYPharmacodynamicsTapentadol is a centrally acting synthetic analgesic combining opioid and non-opioid activity in a single molecule. It has 18 times less binding affinity than morphine to the human mu-opioid receptor but was only 2-3 times less potent in producing analgesia in animal models (on a dose per body weight basis). This low in-vivo potency difference is consistent with its two mechanisms of action. Tapentadol has been shown to inhibit noradrenaline reuptake in the brains of rats resulting in increased . HClNOH(R)(R)
2noradrenaline concentrations. In preclinical models, the analgesic activity due to the mu-opioid receptor agonist activity of tapentadol can be antagonised by selective mu-opioid receptor antagonists (e.g., naloxone), whereas the noradrenaline reuptake inhibition is sensitive to noradrenaline modulators. Tapentadol exerts its analgesic effects directly without a pharmacologically active metabolite.Effects on the cardiovascular system: In repeat dose toxicity studies in conscious dogs, non-persistent QT/QTc interval prolongation was observed at exposures similar to or lower than the clinical plasma Cmax. These effects were not observed in safety pharmacology studies with repeated ECG measurements. Heart rate was increased in conscious rats and dogs at peak plasma concentrations at least twice the clinical plasma Cmax, but there was no clear effect on other ECG parameters (PR interval, QRS duration, T-wave or U-wave morphology). In a thorough QT trial in healthy subjects, no effect of multiple therapeutic and supratherapeutic doses of tapentadol on the QT interval was shown. Similarly, tapentadol had no relevant effect on other ECG parameters (heart rate, PR interval, QRS duration, T-wave or U-wave morphology).PharmacokineticsAbsorptionTapentadol is rapidly and completely absorbed after oral administration of PALEXIA® IR. Mean absolute bioavailability after single-dose administration (fasting) is approximately 32% due to extensive first-pass metabolism. Maximum serum concentrations of tapentadol are typically observed at around 1.25 hours after administration of PALEXIA® IR tablets. Dose-proportional increases in the Cmax and AUC values of tapentadol have been observed after administration of PALEXIA® IR tablets over the oral therapeutic dose range. Steady state serum concentrations of tapentadol are reached on the second day of the treatment regimen. A multiple (every 6 hour) dose study with doses ranging from 75 to 175 mg tapentadol administered as immediate release tablets showed an accumulation ratio between 1.4 and 1.7 for the parent drug and between 1.7 and 2.0 for the major metabolite tapentadol-O-glucuronide, which are primarily determined by the dosing interval and apparent half-life of tapentadol and its metabolite.Food EffectThe AUC and Cmax increased by 25% and 16%, respectively, when PALEXIA® IR tablets were administered after a high-fat, high-calorie breakfast. PALEXIA® IR tablets may be given with or without food.Distribution Tapentadol is widely distributed throughout the body. Following intravenous administration, the volume of distribution (Vz) for tapentadol is 540 +/- 98 L. The serum protein binding is low and amounts to approximately 20%.Metabolism and Elimination In humans, the metabolism of tapentadol is extensive. About 97% of the parent compound is metabolised. The major pathway of tapentadol metabolism is conjugation with glucuronic acid to produce glucuronides. After oral administration approximately 70% (55% glucuronide and 15% sulfate of tapentadol) of the dose is excreted in urine in the conjugated form. Uridine diphosphate glucuronyl transferase (UGT) is the primary enzyme involved in the glucuronidation (mainly UGT1A6, UGT1A9 and UGT2B7 isoforms). A total of 3% of drug was excreted in urine as unchanged drug.