An extended-release injectable formulation of the second-generation antipsychotic aripiprazole (Abilify) has been approved by the FDA (Abilify Maintena – Otsuka/Lundbeck) for once-monthly treatment of schizophrenia. It is the fourth second-generation antipsychotic to become available in a long-acting parenteral formulation. Long-acting parenteral antipsychotics, given at intervals of 2-4 weeks, are generally used for patients with a history of relapse due to poor adherence to oral maintenance therapy.

Invega Hafyera (Janssen), a long-acting, extended-release (ER) formulation of the second-generation antipsychotic paliperidone palmitate, has been approved by the FDA for twice-yearly IM treatment of schizophrenia in adults who have been adequately treated with another injectable ER formulation of the drug (Invega Sustenna or Invega Trinza). It is the first drug to become available in the US for twice-yearly treatment of schizophrenia.

The oral second-generation antipsychotic drug iloperidone (Fanapt – Vanda) has been approved by the FDA for acute treatment of manic or mixed episodes associated with bipolar I disorder in adults. First approved in 2009 for treatment of schizophrenia, iloperidone is the eighth second-generation antipsychotic to be approved for acute treatment of manic or mixed episodes of bipolar I disorder (see Table 1).

The FDA has approved the oral, once-daily, second-generation antipsychotic brexpiprazole (Rexulti – Otsuka/Lundbeck) for treatment of schizophrenia and as an adjunct to antidepressants for treatment of major depressive disorder (MDD). Aripiprazole (Abilify), a structurally similar second-generation antipsychotic also comarketed by Otsuka (with BMS), recently became available generically.

The FDA has approved two new long-acting injectable formulations of second-generation antipsychotics for treatment of schizophrenia: aripiprazole lauroxil (Aristada – Alkermes), which is given once every 4-6 weeks, and paliperidone palmitate (Invega Trinza – Janssen), which is given once every 3 months. Once-monthly injectable formulations of aripiprazole (Abilify Maintena) and paliperidone palmitate (Invega Sustenna) were approved earlier.

The FDA has approved cariprazine (Vraylar – Actavis), an oral, once-daily, second-generation antipsychotic, for treatment of schizophrenia and for acute treatment of manic or mixed episodes associated with bipolar I disorder.

An extended-release formulation of carbamazepine, available since 1997 for treatment of epilepsy, has now been approved under a new name, Equetro, for acute mania and mixed episodes of bipolar disorder. Although the drug was effective in some patients for up to 6 months, it has not been approved for maintenance treatment. Carbamazepine has not been shown to be more effective than lithium or valproate, and it can cause serious adverse effects.

Tetrabenazine (Xenazine - Ovation Pharmaceuticals), an old drug first synthesized 50 years ago for treatment of schizophrenia, was recently approved by the FDA for the treatment of chorea associated with Huntington's disease. It has been available in other countries for decades.

The FDA has approved a sublingual film formulation of the alpha-2 adrenergic receptor agonist dexmedetomidine (Igalmi — BioXcel Therapeutics) for acute treatment of agitation associated with schizophrenia or bipolar I or II disorder in adults. It is the first alpha-2 agonist and the only sublingual film to be approved for this indication. Dexmedetomidine has been available for many years in an injectable formulation (Precedex) for sedation in the intensive care unit and to facilitate procedures such as mechanical ventilation.

Changes caused by one drug in the absorption, distribution, metabolism or excretion of another may lead to a pharmacokinetic adverse drug interaction (DN Juurlink et al, JAMA 2003; 289:1652). Additive drug interactions, such as vasodilation caused by both sildenafil (Viagra) and nitrates, can also have adverse effects.