Use of asenapine transdermal system avoids the dysgeusia and oral hypoesthesia that can be observed with sublingual asenapine4,6; however, dermal effects need to be considered (see Dermal safety). The most commonly observed adverse reactions (incidence ≥5% and at least twice that for placebo) for asenapine transdermal system are extrapyramidal disorder, application site reaction, and weight gain.3 For sublingual asenapine for adults with schizophrenia, the list includes akathisia, oral hypoesthesia, and somnolence.4 These adverse events can be further described using the metric of number needed to harm (NNH) as shown in Table 3.3,4,11,12,14 Of note, extrapyramidal disorder and weight gain appear to be dose-related for asenapine transdermal system. Akathisia appears to be dose-related for sublingual asenapine but not for asenapine transdermal system. Somnolence appears to be associated with sublingual asenapine but not necessarily with asenapine transdermal system.
For sublingual asenapine, the additional indications (bipolar I disorder as acute monotherapy treatment of manic or mixed episodes in adults and pediatric patients age 10 to 17, adjunctive treatment to lithium or valproate in adults, and maintenance monotherapy treatment in adults) have varying commonly encountered adverse reactions.4 Both transdermal asenapine system and sublingual asenapine are contraindicated in patients with severe hepatic impairment (Child-Pugh C) and those with known hypersensitivity to asenapine or to any components in the formulation. Both formulations carry similar warnings in their prescribing information regarding increased mortality in older patients with dementia-related psychosis, cerebrovascular adverse reactions in older patients with dementia-related psychosis, neuroleptic malignant syndrome, tardive dyskinesia, metabolic changes, orthostatic hypotension, leukopenia (and neutropenia and agranulocytosis), QT prolongation, seizures, and potential for cognitive and motor impairment.
Adverse events leading to discontinuation of study treatment in the asenapine transdermal system pivotal trial occurred in 4.9%, 7.8%, and 6.8% of participants in the 3.8 mg/24 hour, 7.6 mg/24 hour, and placebo groups, respectively.11
In the pivotal efficacy study,11 the incidence of adverse events at patch application sites was higher in the active groups vs placebo (Table 33,4,11,12,14). The most frequently reported patch application site reactions were erythema and pruritus, occurring in approximately 10% and 4% in the active treatment arms vs 1.5% and 1.9% for placebo, respectively. With the exception of 1 adverse event of severe application site erythema during Week 2 (participant received 7.6 mg/24 hour, erythema resolved without intervention, and the patient continued the study), all other patch application site events were mild or moderate in severity. Rates of discontinuation due to application site reactions or skin disorders were ≤0.5% across all groups. In the pharmacokinetic studies,10 no patches were removed because of unacceptable irritation.
Asenapine transdermal system is the first antipsychotic “patch” FDA-approved for the treatment of adults with schizophrenia. Asenapine has been available since 2009 as a sublingual formulation administered twice daily. The pharmacokinetic profile of the once-daily transdermal system demonstrates dose-proportional kinetics and sustained delivery of asenapine with a low peak-to-trough plasma level ratio. Three dosage strengths (3.8, 5.7, and 7.6 mg/24 hours) are available, corresponding to blood levels attained with sublingual asenapine exposures of 10, 15, and 20 mg/d, respectively. Application sites are rotated daily and include the upper arms, upper back, abdomen, or hip. Dysgeusia and hypoesthesia of the tongue are avoided with the use of the patch, and there are no food or drink restrictions. Attention will be needed in case of dermal reactions, similar to that observed with other medication patches.