The boosting of didanosine by allopurinol permits a halving of the didanosine dosage

Drug-Drug and Drug-Food Interactions Between Tenofovir Disoproxil Fumarate and Didanosine

The drug-drug and drug-food interactions between tenofovir DF and didanosine EC were evaluated in 2 pharmacokinetic studies in healthy adult subjects. When 400 mg was dosed with tenofovir DF, mean didanosine AUC was increased by 44% to 60% following fasted or fed administration. Staggered coadministration (2 hour, fasted) of a reduced didanosine dose of 250 mg resulted in equivalent didanosine exposure, while simultaneous administration with tenofovir DF in the fasted and fed state resulted in didanosine AUCs similar to that of the reference treatment of 400 mg alone in the fasted state. These data indicate that a dose reduction of didanosine is warranted when it is used with tenofovir DF. The drug-drug-food interaction of didanosine may offer more flexible dosing of didanosine EC when it is used with tenofovir DF. Patients receiving tenofovir DF and didanosine together should be carefully monitored for safety and efficacy.

Quinacrine sterilization for human immunodeficiency virus-positive women

OBJECTIVE

To evaluate the safety of nonsurgical quinacrine sterilization for HIV-positive (HIV+) women.

DESIGN

An open trial of quinacrine sterilization was carried out in women infected with HIV and women who were HIV negative (HIV-). Comparison of the results with the two groups provided an assessment of the safety and effectiveness of quinacrine sterilization for HIV+ women.

SETTING

University Medical School outpatient services.

PATIENT(S)

A total of 258 women who desired sterilization were offered quinacrine sterilization as a means of limiting family size. Sixty-four were HIV+, and 194 were HIV-. Women who were HIV+ had CD4 counts >200 and were otherwise healthy.

INTERVENTION(S)

A modified Copper T intrauterine device inserter was used to place 252 mg of quinacrine, divided into seven pellets (36 mg each) into the uterine cavity. Three insertions of this formulation were performed, 1 month apart. Viral load and CD8 and CD4 lymphocytes were measured both before and after quinacrine sterilization and at follow-up visits. Pregnancies and adverse events were recorded carefully. A decrement life table was made to statistically analyze results. RESULT(S) AND MAIN OUTCOME MEASURE(S): No serious adverse event occurred in any patient in this study. Adverse effects related to quinacrine sterilization were abdominal cramping, vulvar itching, nausea, and vaginal bleeding. Vaginal bleeding was the only short-term side effect noted to occur more frequently in HIV-infected women after quinacrine sterilization. Among HIV+ women, 35.9% had complaints of increased bleeding, whereas only 8.2% of those who were HIV- had such complaints, which probably were insertion related. Viral load and the CD4+ and CD8+ lymphocyte measures displayed no statistically significant difference after quinacrine sterilization.

CONCLUSION(S)

Quinacrine sterilization is a safe method for the sterilization of HIV-infected women and has no short-term effect on the pathology of the disease.

Antiretrovirals, Part II: Focus on Non-Protease Inhibitor Antiretrovirals (NRTIs, NNRTIs, and Fusion Inhibitors)

The second in a series reviewing the HIV/AIDS antiretroviral drugs. This review summarizes the non-protease inhibitor antiretrovirals: nucleoside and nucleotide analogue reverse transcriptase inhibitors (NRTIs), the nonnucleoside reverse transcriptase inhibitors (NNRTIs), and cell membrane fusion inhibitors. In an overview format for primary care physicians and psychiatrists, this review presents the mechanism of action, side effects, toxicities, and drug interactions of these agents.

Role of purine nucleoside phosphorylase in interactions between 2',3'-dideoxyinosine and allopurinol, ganciclovir, or tenofovir

The level of systemic exposure to 2',3'-dideoxyinosine (ddI) is increased 40 to 300% when it is coadministered with allopurinol (Allo), ganciclovir (GCV), or tenofovir. However, the mechanism for these drug interactions remains undefined. A metabolic route for ddI clearance is its breakdown by purine nucleoside phosphorylase (PNP). Consistent with previous reports, enzymatic inhibition assays showed that acyclic nucleotide analogs can inhibit the phosphorolysis of inosine. It was further established that the mono- and diphosphate forms of tenofovir were inhibitors of PNP-dependent degradation of ddI (K(i)s, 38 nM and 1.3 microM, respectively). Allo and its metabolites were found to be relatively weak inhibitors of PNP (K(i)s, >100 microM). Coadministration of tenofovir, GCV, or Allo decreased the amounts of intracellular ddI breakdown products in CEM cells, while they increased the ddI concentrations (twofold increase with each drug at approximately 20 microM). While inhibition of the physiological function of PNP is unlikely due to the ubiquitous presence of high levels of enzymatic activity, phosphorylated metabolites of GCV and tenofovir may cause the increased level of exposure to ddI by direct inhibition of its phosphorolysis by PNP. The discrepancy between the cellular activity of Allo and the weak enzyme inhibition by Allo and its metabolites may be explained by an indirect mechanism of PNP inhibition. This mechanism may be facilitated by the unfavorable equilibrium of PNP and the buildup of one of its products (hypoxanthine) through the inhibition of xanthine oxidase by Allo. These findings support the inhibition of PNP-dependent ddI degradation as the molecular mechanism of these drug interactions.

Effects of chloroquine on viral infections: an old drug against today's diseases?

Chloroquine is a 9-aminoquinoline known since 1934. Apart from its well-known antimalarial effects, the drug has interesting biochemical properties that might be applied against some viral infections. Chloroquine exerts direct antiviral effects, inhibiting pH-dependent steps of the replication of several viruses including members of the flaviviruses, retroviruses, and coronaviruses. Its best-studied effects are those against HIV replication, which are being tested in clinical trials. Moreover, chloroquine has immunomodulatory effects, suppressing the production/release of tumour necrosis factor α and interleukin 6, which mediate the inflammatory complications of several viral diseases. We review the available information on the effects of chloroquine on viral infections, raising the question of whether this old drug may experience a revival in the clinical management of viral diseases such as AIDS and severe acute respiratory syndrome, which afflict mankind in the era of globalisation.