ASENAPINE (Page 6 of 8)
8.5 Geriatric Use
Clinical studies of asenapine in the treatment of bipolar mania did not include sufficient numbers of patients aged 65 and over to determine whether or not they respond differently than younger patients. Of the approximately 2250 patients in pre-marketing clinical studies of asenapine, 1.1% (25) were 65 years of age or over. Multiple factors that might increase the pharmacodynamic response to asenapine, causing poorer tolerance or orthostasis, could be present in elderly patients, and these patients should be monitored carefully. Based on a pharmacokinetic study in elderly patients, dosage adjustments are not recommended based on age alone [see Clinical Pharmacology ( 12.3)].
Elderly patients with dementia-related psychosis treated with asenapine are at an increased risk of death compared to placebo. Asenapine is not approved for the treatment of patients with dementia-related psychosis [see Boxed Warning].
8.6 Renal Impairment
No dosage adjustment for asenapine is required on the basis of a patient’s renal function (mild to severe renal impairment, glomerular filtration rate between 15 and 90 mL/minute). The exposure of asenapine was similar among subjects with varying degrees of renal impairment and subjects with normal renal function [see Clinical Pharmacology ( 12.3)] . The effect of renal function on the excretion of other metabolites and the effect of dialysis on the pharmacokinetics of asenapine has not been studied.
8.7 Hepatic Impairment
Asenapine is contraindicated in patients with severe hepatic impairment (Child-Pugh C) because asenapine exposure is 7-fold higher in subjects with severe hepatic impairment than the exposure observed in subjects with normal hepatic function.
No dosage adjustment for asenapine is required in patients with mild to moderate hepatic impairment (Child-Pugh A and B) because asenapine exposure is similar to that in subjects with normal hepatic function [see Contraindications ( 4) and Clinical Pharmacology ( 12.3)].
8.8 Other Specific Populations
No dosage adjustment for asenapine is required on the basis of a patient’s sex, race (Caucasian and Japanese), or smoking status [see Clinical Pharmacology ( 12.3)] .
9 DRUG ABUSE AND DEPENDENCE
9.1 Controlled Substance
Asenapine is not a controlled substance.
Asenapine has not been systematically studied in animals or humans for its abuse potential or its ability to induce tolerance or physical dependence. Thus, it is not possible to predict the extent to which a CNS-active drug will be misused, diverted and/or abused once it is marketed. Patients should be evaluated carefully for a history of drug abuse, and such patients should be observed carefully for signs that they are misusing or abusing asenapine (e.g., drug-seeking behavior, increases in dose).
Human Experience: In adult pre-marketing clinical studies involving more than 3350 patients and/or healthy subjects, accidental or intentional acute overdosage 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.
Asenapine sublingual tablet(s) 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 (3a RS ,12b RS)-5-Chloro-2-methyl-2,3,3a,12b-tetrahydro-1 H dibenzo[2,3:6,7]oxepino[4,5- c ]pyrrole (2 Z)-2-butenedioate (1:1). Its molecular formula is C 17 H 16 ClNO⋅C 4 H 4 O 4 and its molecular weight is 401.84 (free base: 285.8). The chemical structure is:
Asenapine maleate is a white to off-white powder.
Asenapine sublingual tablet(s), black cherry flavor, is supplied for sublingual administration in tablets containing 5 mg or 10 mg asenapine; inactive ingredients include copovidone, crospovidone, polyoxyl 35 castor oil, mannitol, magnesium stearate, citric acid, butylated hydroxytoluene, silicon dioxide, sodium bicarbonate and black cherry flavor. Black cherry flavor contains maltodextrin, artificial flavors, propylene glycol, triethyl citrate, and caramel color.
12 CLINICAL PHARMACOLOGY
12.1 Mechanism of Action
The mechanism of action of asenapine, in bipolar disorder, is unknown.
Asenapine exhibits high affinity for serotonin 5-HT 1A , 5-HT 1B , 5-HT 2A , 5-HT 2B , 5-HT 2C , 5-HT 5A , 5-HT 6 , and 5-HT 7 receptors (Ki values of 2.5, 2.7, 0.07, 0.18, 0.03, 1.6, 0.25, and 0.11 nM, respectively), dopamine D 2A , D 2B , D 3 , D 4 , and D 1 receptors (Ki values of 1.3, 1.4, 0.42, 1.1, and 1.4 nM, respectively), α 1A , α 2A , α 2B , and α 2C -adrenergic receptors (Ki values of 1.2, 1.2, 0.33 and 1.2 nM, respectively), and histamine H 1 receptors (Ki value 1.0 nM), and moderate affinity for H 2 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 M 1 ).
Following a single 5 mg dose of asenapine, the mean C max was approximately 4 ng/mL and was observed at a mean t max 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 — 25 L/kg), indicating extensive extravascular distribution. Asenapine is highly bound (95%) to plasma proteins, including albumin and α 1 -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
*: When a low dose of 25 mg twice daily fluvoxamine was co-administered with asenapine, a 29% increase in asenapine exposure was observed. Concomitant use of a therapeutic dose of fluvoxamine may cause greater increases in asenapine exposure.
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
*: Asenapine may enhance the inhibitory effects of paroxetine on its own metabolism.
**: In vivo, Asenapine appears to be at most a weak inhibitor of CYP2D6. Following coadministration of dextromethorphan and asenapine in healthy subjects, the ratio of dextrorphan/dextromethorphan (DX/DM) as a marker of CYP2D6 activity was measured. Indicative of CYP2D6 inhibition, treatment with asenapine 5 mg twice daily decreased the DX/DM ratio of 0.43. In the same study, treatment with paroxetine 20 mg daily decreased the DX/DM ratio to 0.032. In a separate study, coadministration of a single 75 mg dose of imipramine with a single 5 mg dose of asenapine did not affect the plasma concentrations of the metabolite dispiramine (a CYP2D6 substrate).
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 30-40% higher as compared to adults.
Figure 3: Effect of Intrinsic Factors on Asenapine Pharmacokinetics
*: Results are based on a cross-trial comparison.
The data shown for renal and hepatic impairment are relative to subjects with normal renal and hepatic function, respectively.
The data shown for smoker are relative to non-smoker.
The data shown for Japanese are relative to Caucasian.
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