Prescription Drug Information: Asenapine (Page 5 of 7)

10 OVERDOSAGE

Human Experience: In adult pre-marketing clinical studies involving more than 3350 patients and/or healthy subjects, accidental or intentional acute over dosage of asenapine was identified in 3 patients. Among these few reported cases of overdose, the highest estimated ingestion of asenapine was 400 mg. Reported adverse reactions at the highest dosage included agitation and confusion.

Management of Overdosage: There is no specific antidote to asenapine. The possibility of multiple drug involvement should be considered. An electrocardiogram should be obtained and management of overdose should concentrate on supportive therapy, maintaining an adequate airway, oxygenation and ventilation, and management of symptoms. Consult with a Certified Poison Control Center for up-to-date guidance and advice on the management of overdosage (1-800-222-1222.)

Hypotension and circulatory collapse should be treated with appropriate measures, such as intravenous fluids and/or sympathomimetic agents (epinephrine and dopamine should not be used, since beta stimulation may worsen hypotension in the setting of asenapine-induced alpha blockade). In case of severe extrapyramidal symptoms, anticholinergic medication should be administered. Close medical supervision and monitoring should continue until the patient recovers.

11 DESCRIPTION

Asenapine sublingual tablet contains asenapine maleate which is an atypical antipsychotic that is available for sublingual administration. Asenapine belongs to the class dibenzo-oxepino pyrroles. The chemical designation is (3aRS ,12bRS)-5-Chloro-2-methyl-2,3,3a,12b-tetrahydro-1H dibenzo[2,3:6,7]oxepino[4,5-c ]pyrrole (2Z)-2 butenedioate (1:1). Its molecular formula is C17 H16 ClNO⋅C4 H4 O4 and its molecular weight is 401.84 (free base: 285.8). The chemical structure is:

Structure
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Asenapine maleate is off-white to white powder.

Asenapine is supplied for sublingual administration in tablets containing 2.5-mg, 5-mg or 10-mg asenapine; inactive ingredients include povidone, butylated hydroxy toluene, butylated hydroxy anisole, mannitol, low-substituted hydroxypropyl cellulose, sodium stearyl fumarate.

12 CLINICAL PHARMACOLOGY

12.1 Mechanism of Action

The mechanism of action of asenapine in bipolar I disorder is unknown.

12.2 Pharmacodynamics

Asenapine exhibits high affinity for serotonin 5-HT1A , 5-HT1B , 5-HT2A , 5-HT2B , 5-HT2C , 5-HT5A , 5-HT6 , and 5-HT7 receptors (Ki values of 2.5, 2.7, 0.07, 0.18, 0.03, 1.6, 0.25, and 0.11 nM, respectively), dopamine D2A , D2B , D3 , D4 , and D1 receptors (Ki values of 1.3, 1.4, 0.42, 1.1, and 1.4 nM, respectively), α1A , α2A , α2B , and α2C -adrenergic receptors (Ki values of 1.2, 1.2, 0.33 and 1.2 nM, respectively), and histamine H1 receptors (Ki value 1 nM), and moderate affinity for H2 receptors (Ki value of 6.2 nM). In in vitro assays asenapine acts as an antagonist at these receptors. Asenapine has no appreciable affinity for muscarinic cholinergic receptors (e.g., Ki value of 8128 nM for M1 ).

12.3 Pharmacokinetics

Following a single 5 mg dose of asenapine, the mean Cmax was approximately 4 ng/mL and was observed at a mean tmax of 1 hour. Elimination of asenapine is primarily through direct glucuronidation by UGT1A4 and oxidative metabolism by cytochrome P450 isoenzymes (predominantly CYP1A2). Following an initial more rapid distribution phase, the mean terminal half-life is approximately 24 hrs. With multiple-dose twice-daily dosing, steady-state is attained within 3 days. Overall, steady-state Asenapine pharmacokinetics are similar to single-dose pharmacokinetics.

Absorption: Following sublingual administration, asenapine is rapidly absorbed with peak plasma concentrations occurring within 0.5 to 1.5 hours. The absolute bioavailability of sublingual asenapine at 5 mg is 35%. Increasing the dose from 5 mg to 10 mg twice daily (a two-fold increase) results in less than linear (1.7 times) increases in both the extent of exposure and maximum concentration. The absolute bioavailability of asenapine when swallowed is low (<2% with an oral tablet formulation).

The intake of water several (2 or 5) minutes after asenapine administration resulted in decreased asenapine exposure. Therefore, eating and drinking should be avoided for 10 minutes after administration [see Dosage and Administration (2.1)].

Distribution: Asenapine is rapidly distributed and has a large volume of distribution (approximately 20 to 25 L/kg), indicating extensive extravascular distribution. Asenapine is highly bound (95%) to plasma proteins, including albumin and α1 -acid glycoprotein.

Metabolism and Elimination: Direct glucuronidation by UGT1A4 and oxidative metabolism by cytochrome P450 isoenzymes (predominantly CYP1A2) are the primary metabolic pathways for asenapine.

Asenapine is a high clearance drug with a clearance after intravenous administration of 52 L/h. In this circumstance, hepatic clearance is influenced primarily by changes in liver blood flow rather than by changes in the intrinsic clearance, i.e., the metabolizing enzymatic activity. Following an initial more rapid distribution phase, the terminal half-life of asenapine is approximately 24 hours. Steady-state concentrations of asenapine are reached within 3 days of twice daily dosing.

After administration of a single dose of [14 C]-labeled asenapine, about 90% of the dose was recovered; approximately 50% was recovered in urine, and 40% recovered in feces. About 50% of the circulating species in plasma have been identified. The predominant species was asenapine N+ -glucuronide; others included N-desmethylasenapine, N-desmethylasenapine N-carbamoyl glucuronide, and unchanged asenapine in smaller amounts. Asenapine activity is primarily due to the parent drug.

In vitro studies indicate that asenapine is a substrate for UGT1A4, CYP1A2 and to a lesser extent CYP3A4 and CYP2D6. Asenapine is a weak inhibitor of CYP2D6. Asenapine does not cause induction of CYP1A2 or CYP3A4 activities in cultured human hepatocytes. Coadministration of asenapine with known inhibitors, inducers or substrates of these metabolic pathways has been studied in a number of drug-drug interaction studies [see Drug Interactions (7.1)].

Food: A crossover study in 26 healthy adult male subjects was performed to evaluate the effect of food on the pharmacokinetics of a single 5 mg dose of asenapine. Consumption of food immediately prior to sublingual administration decreased asenapine exposure by 20%; consumption of food 4 hours after sublingual administration decreased asenapine exposure by about 10%. These effects are probably due to increased hepatic blood flow.

In clinical trials establishing the efficacy and safety of asenapine, patients were instructed to avoid eating for 10 minutes following sublingual dosing. There were no other restrictions with regard to the timing of meals in these trials [see Dosage and Administration (2.1)].

Water: In clinical trials establishing the efficacy and safety of asenapine, patients were instructed to avoid drinking for 10 minutes following sublingual dosing. The effect of water administration following 10 mg sublingual asenapine dosing was studied at different time points of 2, 5, 10, and 30 minutes in 15 healthy adult male subjects. The exposure of asenapine following administration of water 10 minutes after sublingual dosing was equivalent to that when water was administered 30 minutes after dosing. Reduced exposure to asenapine was observed following water administration at 2 minutes (19% decrease) and 5 minutes (10% decrease) [see Dosage and Administration (2.1)].

Drug Interaction Studies:

Effects of other drugs on the exposure of asenapine are summarized in Figure 1. In addition, a population pharmacokinetic analysis indicated that the concomitant administration of lithium had no effect on the pharmacokinetics of asenapine. Figure 1: Effect of Other Drugs on Asenapine Pharmacokinetics

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The effects of asenapine on the pharmacokinetics of other co-administered drugs are summarized in Figure 2. Coadministration of paroxetine with asenapine caused a two-fold increase in the maximum plasma concentrations and systemic exposure of paroxetine. Asenapine enhances the inhibitory effects of paroxetine on its own metabolism by CYP2D6.

Figure 2: Effect of Asenapine on Other Drug Pharmacokinetics

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Studies in Special Populations:

Exposures of asenapine in special populations are summarized in Figure 3. Additionally, based on population pharmacokinetic analysis, no effects of sex, race, BMI, and smoking status on asenapine exposure were observed. Exposure in elderly patients is 30 to 40% higher as compared to adults.

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13 NONCLINICAL TOXICOLOGY

13.1 Carcinogenesis, Mutagenesis, Impairment of Fertility

Carcinogenesis: In a lifetime carcinogenicity study in CD-1 mice asenapine was administered subcutaneously at doses up to those resulting in plasma levels (AUC) estimated to be 5 times those in humans receiving the MRHD of 10 mg twice daily. The incidence of malignant lymphomas was increased in female mice, with a no-effect dose resulting in plasma levels estimated to be 1.5 times those in humans receiving the MRHD. The mouse strain used has a high and variable incidence of malignant lymphomas, and the significance of these results to humans is unknown. There were no increases in other tumor types in female mice. In male mice, there were no increases in any tumor type.

In a lifetime carcinogenicity study in Sprague-Dawley rats, asenapine did not cause any increases in tumors when administered subcutaneously at doses up to those resulting in plasma levels (AUC) estimated to be 5 times those in humans receiving the MRHD.

Mutagenesis: No evidence for genotoxic potential of asenapine was found in the in vitro bacterial reverse mutation assay, the in vitro forward gene mutation assay in mouse lymphoma cells, the in vitro chromosomal aberration assays in human lymphocytes, the in vitro sister chromatid exchange assay in rabbit lymphocytes, or the in vivo micronucleus assay in rats.

Impairment of Fertility: Asenapine did not impair fertility in rats when tested at doses up to 11 mg/kg twice daily given orally. This dose is 10 times the maximum recommended human dose of 10 mg twice daily given sublingually on a mg/m2 basis.

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