Absence of clinically relevant drug interactions following simultaneous administration of didanosine-encapsulated, enteric-coated bead formulation with either itraconazole or fluconazole

A Cohort Study of the Food Effect on Virological Failure and Treatment Discontinuation in Patients on HAART Containing Didanosine Enteric-Coated Capsules (FOODDIe Study)

BACKGROUND

Didanosine enteric-coated capsules (ddI-EC) should be taken under fasting conditions. However, the effect of food on the absorption of ddI-EC may not reduce exposure to the drug.

METHOD

We performed an observational study to assess the effect on virological failure of taking ddI-EC with food. To be included, patients had to have begun their first ddI-EC-containing HAART regimen between June 1, 2001 and June 1, 2003. Primary endpoints were virological failure or discontinuation of the ddI-EC-containing regimen.

RESULTS

668 patients were included (119 patients were naïve, 172 switched from a different regimen, and 377 were part of rescue therapy). 296 patients were taking ddI-EC with food. After 71 weeks of follow-up, 162 discontinued ddI-EC in the fasting group and 120 in the fed group. 46 patients had virological failure (19 without food vs. 27 in the group with food). Adherence to therapy >80% was 79.7%. We fitted a multivariate Cox proportional hazard model and found a significant interaction between ddI-EC intake and adherence. The multivariate model showed that when adherence to HAART was poor (<80% of prescribed pills) taking ddI-EC with food significantly increased the risk of virological failure (hazard ratio [HR] 8.32, 95% CI 1.67-41.65), but this disappeared when adherence was 80%-95% (HR 0.27, 95% CI 0.04-1.53) or >95% (HR 0.57, 95% CI 0.12-2.77).

CONCLUSION

When adherence is good (>80% of the prescribed doses), ddI-EC can be administered with food without an increase in virological failure or HAART discontinuation.

Drug-drug interactions of antifungal agents and implications for patient care

Drug interactions in the gastrointestinal tract, liver and kidneys result from alterations in pH, ionic complexation, and interference with membrane transport proteins and enzymatic processes involved in intestinal absorption, enteric and hepatic metabolism, renal filtration and excretion. Azole antifungals can be involved in drug interactions at all the sites, by one or more of the above mechanisms. Consequently, azoles interact with a vast array of compounds. Drug-drug interactions associated with amphotericin B formulations are predictable and result from the renal toxicity and electrolyte disturbances associated with these compounds. The echinocandins are unknown cytochrome P450 substrates and to date are relatively devoid of significant drug-drug interactions. This article reviews drug interactions involving antifungal agents that affect other agents and implications for patient care are highlighted.

Coccidioidomycosis in Persons Infected with HIV Type 1

Coccidioidomycosis is a recognized opportunistic infection among persons infected with human immunodeficiency virus (HIV). Early in the HIV epidemic, most cases presented as overwhelming diffuse pulmonary disease with a high mortality rate. Although these cases are still seen, patients without significant immunodeficiency frequently present with a community-acquired pneumonia syndrome. Diagnosis can be established by cytological staining, culture, or serologic testing. All patients with HIV infection and symptomatic coccidioidomycosis should be treated with antifungal therapy. Severe cases frequently require a combination of therapy with amphotericin B and a triazole antifungal. Therapy for at least 1 year is recommended, but for patients with a focal pulmonary infection and peripheral blood CD4 lymphocyte counts of >250 cells/microL, it may be reasonable to stop therapy after this time. Other manifestations of coccidioidomycosis require prolonged therapy, and life-long treatment is recommended for persons with meningitis.

Reduced oral itraconazole bioavailability by antacid suspension

AIMS

To investigate the effects of antacid suspension on oral absorption of itraconazole.

METHODS

A randomized, open-labelled, two-period, crossover study with a 1-week washout period was conducted in 12 healthy Thai male volunteers. The participants were allocated in either treatment A or B in the first period. In treatment A, the volunteers were orally administered with 200 mg of itraconazole alone. In treatment B, the volunteers were administered orally with 200 mg of itraconazole co-administered with antacid suspension. Serial serum samples were collected over the period of 24 h and subsequently analysed by using a validated high-pressure liquid chromatographic method with ultraviolet detection. Pharmacokinetic parameters were determined by non-compartmental analysis.

RESULTS

Time to reach maximal concentration (Tmax), maximal concentration (Cmax) and area under the curve (AUC0-infinity) were markedly decreased in antacid-treated group. Tmax for treatment A was 3.0 +/- 0.4 and 5.1 +/- 2.7 h for treatment B. Cmax and AUC0-infinity of treatments A and B were 146.3 +/- 70.5 vs. 43.6 +/- 16.9 (ng/mL) and 1928.5 +/- 1114.6 vs. 654.8 +/- 452.2 (ng x h/mL) respectively. 90% Confidence interval (90% CI) of Cmax and AUC0--infinity were 24.1-42.1 and 16.2-65.9 respectively.

CONCLUSIONS

Rate and extent of itraconazole oral absorption were markedly decreased by concurrent use of antacid suspension. Hence, co-administration of itraconazole and antacid suspension should be avoided.

HAART with didanosine once versus twice daily: adherence and efficacy

BACKGROUND

Highly active antiretroviral therapy (HAART) containing didanosine taken twice daily was compared with HAART containing didanosine taken once daily in terms of adherence and efficacy.

METHOD

This was a self-controlled prospective cohort study, carried out in a tertiary level hospital. A total of 49 HIV-infected patients were included. They were prescribed HAART according to guidelines. After six months taking HAART containing didanosine twice daily, patients continued with the same regimen of HAART although once daily. Thereafter they were followed up for a further nine months. Adherence and virological efficacy were assessed at three-month intervals, for a total of six times, in every patient.

RESULTS

Overall, adherence was poor, with only 19 patients (39%) showing adequate adherence for all six visits. Adequate adherence was observed in 29 patients (59%) three months before didanosine switching, and in 37 patients (75%) three months after didanosine switching (P=0.034). Pooled HIV RNA results of the first three visits were higher than the same results of the last three visits (P=0.05).

CONCLUSIONS

Non-adherence is common among patients who take HAART. Simplification of regimens is useful to improve adherence and efficacy.