Comparisons of oxidative metabolism and reductive capacity in sulfonamide-tolerant and -intolerant patients with human immunodeficiency virus

Hepatic expression profiles in retroviral infection: relevance to drug hypersensitivity risk

HIV‐infected patients show a markedly increased risk of delayed hypersensitivity (HS) reactions to potentiated sulfonamide antibiotics (trimethoprim/sulfamethoxazole or TMP/SMX). Some studies have suggested altered SMX biotransformation in HIV infection, but hepatic biotransformation pathways have not been evaluated directly. Systemic lupus erythematosus (SLE) is another chronic inflammatory disease with a higher incidence of sulfonamide HS, but it is unclear whether retroviral infection and SLE share risk factors for drug HS. We hypothesized that retroviral infection would lead to dysregulation of hepatic pathways of SMX biotransformation, as well as pathway alterations in common with SLE that could contribute to drug HS risk. We characterized hepatic expression profiles and enzymatic activities in an SIV‐infected macaque model of retroviral infection, and found no evidence for dysregulation of sulfonamide drug biotransformation pathways. Specifically, NAT1,NAT2,CYP2C8,CYP2C9,CYB5R3,MARC1/2, and glutathione‐related genes (GCLC,GCLM,GSS,GSTM1, and GSTP1) were not differentially expressed in drug naïve SIVmac239‐infected male macaques compared to age‐matched controls, and activities for SMX N‐acetylation and SMX hydroxylamine reduction were not different. However, multiple genes that are reportedly over‐expressed in SLE patients were also up‐regulated in retroviral infection, to include enhanced immunoproteasomal processing and presentation of antigens as well as up‐regulation of gene clusters that may be permissive to autoimmunity. These findings support the hypothesis that pathways downstream from drug biotransformation may be primarily important in drug HS risk in HIV infection.

Differential toxicity of reactive metabolites of clindamycin and sulfonamides in HIV-infected cells: influence of HIV infection on clindamycin toxicity in vitro

Hypersensitivity adverse drug reactions are much more common among patients with acquired immunodeficiency syndrome (AIDS) than in the general population. High rates of hypersensitivity reactions to clindamycin have been noted. To investigate the role of reactive metabolites in these reactions, the authors studied toxicity of clindamycin and sulphamethoxazole (SMX) and their metabolites in uninfected and human immunodeficiency virus (HIV)-infected MOLT3 cells. Infected and uninfected cells were incubated with clindamycin or sulphamethoxazole hydroxylamine in increasing concentrations; reactive metabolites were generated by coincubation of cells and drug with murine microsomes and a microsomal activating system. Over a concentration range of 0 to 400 microM SMX-HA, there was a significant concentration-dependent increase in cell death in HIV-infected compared to uninfected cells (28%+/-3% vs 8%+/-5% at 400 microM, P < .05). In contrast, coincubation of cells with clindamycin, microsomes, and a microsomal activating system, as well as combinations of primaquine or pyrimethamine, was not associated with an increase in cell death among infected compared to uninfected cells. No concentration-toxicity was demonstrated. These data support the role of reactive metabolites in adverse drug reactions to sulfonamides during HIV infection, whereas alternate mechanism(s) may be responsible for increased rates of adverse drug reactions to clindamycin among patients with AIDS.

The effect of cimetidine on the formation of sulfamethoxazole hydroxylamine in patients with human immunodeficiency virus

Hypersensitivity reactions from trimethoprim/sulfamethoxazole are likely caused by a reactive nitroso intermediate formed from sulfamethoxazole hydroxylamine. This pilot study tested whether cimetidine inhibits the urinary excretion of sulfamethoxazole hydroxylamine. Ten outpatients infected with human immunodeficiency virus (HIV) and currently receiving trimethoprim/sulfamethoxazole prophylaxis were randomly selected from 59 eligible patients. Five received cimetidine 800 mg twice daily for 1 week and five served as controls. Two spot urine samples one week apart were obtained after a trimethoprim/sulfamethoxazole dose for all patients. Patients taking cimetidine had a significant decrease in excretion of sulfamethoxazole hydroxylamine relative to total excreted drug in the two urine samples compared with control patients. Cimetidine likely caused this decrease in sulfamethoxazole hydroxylamine excretion through inhibition of CYP3A4. Because of potential differences between HIV-infected patients and healthy subjects in oxidative metabolism, future studies of inhibitors of sulfamethoxazole hydroxylamine formation should be conducted in the HIV population.