Mr. S, age 56, has human immunodeficiency virus (HIV) and schizoaffective disorder. He presents to your clinic with increased auditory hallucinations, disorganized behavior, and worsened tremors that have begun to seriously disrupt his daily life. Mr. S is prescribed risperidone; however, he reports that he has not been taking it lately due to the tremor despite being controlled on his medication regimen for nearly 1 year. His Abnormal Involuntary Movement Scale (AIMS) score reveals an increased wrist rigidity compared with previous clinic visits. Mr. S has a 40 pack-year history of smoking and history of IV drug use. Furthermore, he has a medical history of type 2 diabetes mellitus, hypertension, and hyperlipidemia.
His medication regimen includes atazanavir sulfate, 200 mg/d, ritonavir, 100 mg/d, efavirenz/emtricitabine/tenofovir disoproxil fumarate, 600/200/300 mg/d, risperidone, 6 mg/d, bupropion extended-release, 300 mg/d, gabapentin, 600 mg/d, amlodipine, 5 mg/d, pravastatin, 40 mg/d, metformin, 1000 mg twice daily, and glipizide, 10 mg twice daily. Today, his laboratory findings show that his CD4 count is 405 cell/mm3, and his viral load is <40 copies/mL, indicating his HIV is well managed. A hepatitis C virus antibody test result is negative and serum creatinine level is 1.0 mg/dL. Total cholesterol is 212 mg/dL, high-density lipoprotein cholesterol is 43 mg/dL, low-density lipoprotein cholesterol is 121 mg/dL, and triglycerides level is 238 mg/dL. Electrocardiography reveals a QTc interval of 426 ms. Mr. S’s blood pressure is 105/65 mm Hg. Based on this clinic visit, the treatment team decides to change Mr. S’s antipsychotic.
Psychiatric illness and HIV/AIDS
There is a strong link between mental illness and HIV/AIDS; 50% or more of patients with HIV/AIDS have a comorbid psychiatric disorder.1 The prevalence of mental illness in patients with HIV/AIDS is reported to be 8 times higher than in those without HIV/AIDS.2 Depression, bipolar disorder, anxiety disorders, delirium, substance abuse, and schizophrenia have all been identified in persons receiving highly active antiretroviral therapy (HAART). Patients with HIV/AIDS and psychiatric illness have a decreased quality of life, poor adherence to medications, faster disease progression, and increased mortality. Care of these individuals is complicated by the stigma of HIV/AIDS and the prevalence of the illness in underserved populations, as well as the need for complex medication regimens and the possibility of drug–drug interactions (DDIs).1,2 If left untreated, psychiatric illness in patients with HIV/AIDS may lead to further transmission of HIV as a result of patients engaging in high-risk behaviors, along with poor adherence to HAART.3
Individuals diagnosed with schizophrenia, schizoaffective disorder, and bipolar disorder are at greater risk for HIV infection.3 Patients with HIV/AIDS with primary psychosis may have poor medication adherence rates due to illness-related confusion or paranoia about medications. Furthermore, they may lack the resources to manage the complications and stress related to living with HIV/AIDS.
New-onset, or secondary psychosis, has been reported in individuals with late-stage HIV/AIDS with CD4 counts <200 who have not been diagnosed with a psychotic disorder previously.3 These patients may experience more persecutory and grandiose delusions rather than hallucinations. Neuropsychiatric symptoms in patients with HIV/AIDS may be due to the presence of HIV or other infections in the CNS, tumors, or other inflammatory illnesses. Medications that have been implicated in neuropsychiatric symptoms include efavirenz, rilpivirine, and other HAART regimens; interferon; metoclopramide; corticosteroids; muscle relaxants; and clonidine. It is possible that symptoms may continue even after the medications are discontinued.3
Antipsychotics remain the treatment of choice for psychosis in HIV/AIDS, regardless of the cause of the symptoms. Many factors must be taken into consideration when choosing an antipsychotic, such as DDIs, adverse effect profiles, patient history of antipsychotic use, cost, and patient preference. Here we focus primarily on DDIs and adverse effect profiles.
When treating psychosis in patients with HIV/AIDS, it is crucial to consider potential DDIs. Many antipsychotics and antiretroviral medications utilize cytochrome P450 (CYP) enzymes for their metabolism. The CYP enzyme system is responsible for the oxidative reactions that constitute the phase I reactions necessary for the metabolism of most drugs. Inhibition and induction of CYP enzymes are among the most common causes of pharmacokinetic DDIs. Antipsychotics are predominately metabolized by CYP3A4, CYP1A2, and CYP2D6.4
Continue to: The DDIs arise because...