Dosing for Bactrim PJ is a 37-year-old HIV-infected man who comes to the pharmacy with a new prescription for Bactrim (trimethoprim and sulfamethoxazole)—1 double-strength tablet daily for prophylaxis of pneumocystis pneumonia (PCP). PJ’s CD4 count is 177 cells/mcL. PJ has been filling prescriptions for antiretroviral therapy at the pharmacy for many years. While filling the Bactrim prescription, the pharmacist recalls a prescription he filled for an HIV-infected patient requiring PCP prophylaxis a few weeks back for Bactrim 1 single-strength tablet daily. The pharmacist begins to question what the correct dose of Bactrim is for this indication.
What is the appropriate dose of Bactrim for this indication?
Case Two: Adjuncts to Peginterferon Alfa-2a Therapy JC is a 32-year-old man with hepatitis C whose liver biopsy shows chronic hepatitis with significant fibrosis. His physical exam and blood work show he does not have decompensated liver disease (marked by hepatic encephalopathy or ascities) or abnormalities on his complete blood count or metabolic chemistry panel. JC has no other comorbidities. He was just seen by a physician and a pharmacist at the clinic he attends, and the physician decided to start peginterferon alfa-2a (180 mcg subcutaneously once weekly) and ribavirin (1200 mg, because JC weighs 82 kg). The pharmacist knows that fewer than 50% of patients will respond to therapy.
Is there anything the pharmacist could recommend be added to peginteferon alfa-2a and ribavirin to increase JC’s chances of a positive outcome?
Case 1: V The National Institutes of Health/Centers for Disease Control and Prevention/Infectious Diseases Society of America guidelines for the prevention and treatment of opportunistic infections in HIV-infected adults and adolescents (www.cdc.gov/mmwr/pdf/rr/rr5804.pdf) recommend Bactrim be administered to HIV-injected patients such as PJ whose CD4 counts fall below 200 cells/mcL to prevent PCP. The preferred regimen listed in the guidelines is 1 double-strength tablet daily; however, 1 double-strength tablet 3 times weekly and 1 single-strength tablet daily are noted as also likely being effective. The latter is also touted as having better tolerability than the preferred regimen. Therefore, the pharmacist should not be concerned with PJ’s dose of Bactrim (as he is getting the preferred regimen), nor worry that the previous patient was getting an ineffective dose for PCP prophylaxis.
Case 2: Two new nonstructural protein 3 (NS3)/4A serine protease inhibitors (boceprevir [Victrelis] and telaprevir [Incivek]) have been recently approved by the FDA for the treatment of chronic hepatitis C infection. Clinical trials have demonstrated that patients receiving either of these medications in addition to standard-of-care therapy of peginterferon alfa-2a and ribavirin experienced a greater likelihood of achieving a sustained virologic response (undetectable virus levels 24 weeks after - stopping therapy), with about two-thirds to three-fourths of patients treated with a serine prote - ase inhibitor achieving this end point. Achieving a sustained virologic response has been associ ated with a decreased risk of liver complications, cirrhosis, liver cancer, and mortality. The pharmacist could recommend either boceprevir or telaprevir be added to JC’s peginterferon alfa-2a and ribavirin therapy with dosing and scheduling consistent with recommendations in these drugs’ prescribing information. Of note, both of these serine protease inhibitors utilize “response-guided therapy” (duration of therapy dictated by viral response). Thus, the physician and pharmacist should monitor virus levels and adjust the duration of therapy according to the recommendations provided in each drug’s prescribing information.
Dr. Coleman is associate professor of pharmacy practice and director of the pharmacoeconomics and outcomes studies group at the University of Connecticut School of Pharmacy.