Interaction between enfuvirtide, an injectable fusion inhibitor, and niacin in an HIV-infected patient.
OBJECTIVE
To report a potential drug-drug interaction between enfuvirtide, an injectable HIV fusion inhibitor, and niacin in an HIV-infected man with dilated cardiomyopathy.


METHODS
A 47-year-old HIV-infected man with dilated cardiomyopathy and prolonged QT syndrome with an automatic implantable cardiovascular defibrillator device was prescribed subcutaneous enfuvirtide 90 mg twice daily as part of his antiretroviral regimen and oral extended-release niacin 500 mg/day for a high-density lipoprotein level of 8 mg/dL. After 1 week of concomitant therapy, the patient began experiencing extreme redness, edema, and swelling at the injection site that corresponded with the flushing sensation due to niacin. This interfered with his daily activities, leading to self-discontinuation of both agents. As the patient had tolerated enfuvirtide therapy prior to the addition of niacin, we reinitiated enfuvirtide with close follow-up, and the patient has been maintained on this agent since then without consequence. Based on the Horn Drug Interaction Probability Scale, a probable interaction occurred between enfurvirtide and niacin.


CONCLUSIONS
We hypothesize that a drug-drug interaction occurs between enfuvirtide and niacin related to prostaglandin synthesis and mobilization of inflammatory cells, specifically Langerhans cells. A theoretical mechanism for this interaction is that the Langerhans cells in the epidermis function improperly due to the presence of HIV and the attachment of enfuvirtide. When these cells are exposed to nicotinic acid, an exaggerated immune response is produced that may lead to pain, redness, and swelling at the injection site. Prostaglandins, cytokines, and other inflammatory molecules may all have a role in this interaction.


CONCLUSIONS
Caution should be used when coadministering enfuvirtide and niacin to HIV-infected patients.
Pharmacotherapy Education and Research Center, College of Pharmacy, University of Texas, The University of Texas Health Science Center, San Antonio, TX, USA.
Elizabeth
E
Oates
Kathryn
K
Dzintars
D003692:Delayed-Action Preparations / Q000009:adverse effects*; D004347:Drug Interactions; D024882:Drug Resistance, Viral / Q000187:drug effects; D000077560:Enfuvirtide; D015700:HIV Envelope Protein gp41 / Q000008:administration & dosage / Q000009:adverse effects*; D023581:HIV Fusion Inhibitors / Q000008:administration & dosage / Q000009:adverse effects*; D015658:HIV Infections / Q000188:drug therapy*; D006801:Humans; D000960:Hypolipidemic Agents / Q000008:administration & dosage / Q000009:adverse effects*; D007279:Injections, Subcutaneous / Q000009:adverse effects; D008297:Male; D008875:Middle Aged; D009525:Niacin / Q000008:administration & dosage / Q000009:adverse effects*; D010446:Peptide Fragments / Q000008:administration & dosage / Q000009:adverse effects*
D003692:Delayed-Action Preparations; D015700:HIV Envelope Protein gp41; D023581:HIV Fusion Inhibitors; D000960:Hypolipidemic Agents; D010446:Peptide Fragments; D000077560:Enfuvirtide; D009525:Niacin