Drug‐Drug Interaction between Itraconazole and the Antiretroviral Drug Lopinavir/Ritonavir in an HIV‐1–Infected Patient with Disseminated Histoplasmosis

Histoplasmosis in patients living with HIV in Europe: review of literature

Histoplasma capsulatum (var. capsulatum Hcc and duboisii Hcd), is a dimorphic fungus that causes histoplasmosis. It usually affects people coming from endemic areas, causing a variety of clinical manifestations up to progressive disseminated histoplasmosis (PDH), especially among people living with HIV (PLWH). We conducted a systematic review to assess histoplasmosis burden of PLWH in Europe. The review follows PRISMA guidelines, with protocol registered in PROSPERO (CRD42023429779). Seventy-eight articles were selected, including 109 patients (32 women). On overall, median age was 37 years. Forty-six patients were Americans, 39 Africans, 17 Europeans, 5 Asians, in 2 cases nationality was not specified. Cases were mainly diagnosed in Italy (28.4%), France (17.3%) and Spain (17.4%), with a north-south gradient. Six cases lacked epidemiologic links with endemic areas. Concerning CDC HIV staging at diagnosis, the information was available for 60 PLWH (55%) and all subjects were at stage C3 except for two subjects at stage B3. PDH was the AIDS-presenting illness in 39 patients. Most patients had a PDH (80.7%); other common extrapulmonary forms were isolated cutaneous histoplasmosis (7.3%), or lymphatic localization (2.7%). In 30 cases, the diagnosis was made by analyzing only one sample. For the remaining 79 cases, multiple samples were collected from each patient. Regarding the biological sample more frequently used for the diagnosis of histoplasmosis, bronchoalveolar lavage sample was taken from 39 patients, and tested positive in 51.3% of cases; 36 patients underwent a skin biopsy which was positive in 86.1% of cases and 28 patients performed bone-marrow biopsy, which led to the diagnosis of histoplasmosis in 92.9% of cases. The identification of Histoplasma capsulatum was available in 97 PLWH through examination of different samples: Hcc and Hcd were identified in 89 and 8 PLWH, respectively. Concerning therapies, 67.9% were treated with liposomal amphotericin B, 18.3% with itraconazole, 10 died pre-treatment. The overall mortality rate was 23.6%. Non-survivors exhibited more frequently gastrointestinal symptoms (p = 0.017), while cutaneous signs correlated with better survival (p = 0.05). Untreated patients faced higher mortality (p < 0.001). Histoplasmosis should be considered amongst opportunistic infection in PLWH, even in Europe, especially if patients originate from or have travelled to endemic areas. Systematic review registration: The registration number is CRD42023429779.

A case report of a prolonged decrease in tacrolimus clearance due to co-administration of nirmatrelvir/ritonavir in a lung transplant recipient receiving itraconazole prophylaxis

BACKGROUND

Drug-drug interaction management is complex. Nirmatrelvir/ritonavir is a potent cytochrome P450 (CYP) 3A inhibitor and influences pharmacokinetics of co-administered drugs. Although there are several reports about drug-drug interactions of nirmatrelvir/ritonavir, an influence of a concomitant use of nirmatrelvir/ritonavir and another potent CYP3A inhibitor on tacrolimus remains unclear. Here, we experienced a lung transplant patient with the novel coronavirus disease 2019 (COVID-19). In this patient, nirmatrelvir/ritonavir was administered, and the inhibitory effect of itraconazole on CYP3A was prolonged.

CASE PRESENTATION

We present a case in forties who had undergone lung transplantation. He was administered itraconazole and tacrolimus 1.0 mg/d, with a trough value of 8-12 ng/mL. The patient contracted the COVID-19, and a nirmatrelvir/ritonavir treatment was initiated. During the antiviral treatment, tacrolimus administration was discontinued for 5 d. Tacrolimus was resumed at 1.0 mg/d after completion of the nirmatrelvir/ritonavir treatment, but the trough value after 7 d was high at 31.6 ng/mL. Subsequently, the patient was placed on another 36-h tacrolimus discontinuation, but the trough value decreased to only 16.0 ng/mL.

CONCLUSIONS

Co-administration of ritonavir caused a prolonged decrease in tacrolimus clearance through its inhibitory effects on CYP3A in a patient taking itraconazole. Management of drug-drug interaction by pharmacists can be important for patients with multiple medications.

Talaromycosis marneffei of the Cervical Spine: An Unusual Infection

Talaromyces marneffei infection (TMI) causing vertebral osteomyelitis of the cervical spine is extremely rare. TMI in an HIV-uninfected patient is also unusual. This report presents the successful treatment of an HIV-uninfected TMI patient who underwent C6 and T1 vertebrectomies, bone grafting, and anterior cervical plating accompanied by antifungal therapy. A 63-year-old woman was diagnosed with adult-onset immune deficiency. She suddenly developed progressive neck pain without neurologic deficit. The plain radiographs and magnetic resonance imaging showed inflammation and abscess formation along the prevertebral area from C3-4 to T2-3 with vertebral body destruction. Intraoperative pus culture and tissue specimens were determined to be T marneffei. The patient was treated intravenously with amphotericin B deoxycholate for 4 weeks (0.6 mg/kg/d) and oral itraconazole (400 mg/d) for 12 months. Over a 2 consecutive year follow-up period, she achieved a full recovery with an absence of neck pain.

Clinical Characteristics and Prognosis of Penicilliosis Among Human Immunodeficiency Virus-Infected Patients in Eastern China

AbstractTalaromyces marneffei infection is increasingly observed in people living with human immunodeficiency virus (HIV) in eastern China, a nonendemic area. This study aimed to draw the clinician's attention to this disease by presenting the clinical characteristics and prognosis of penicilliosis among HIV-infected patients from this region. We retrospectively analyzed HIV-infected patients with culture-proven T. marneffei infection admitted during January 1, 2014-December 31, 2015, at the Shanghai Public Health Clinical Center. A total of 48 patients with confirmed HIV infection and penicilliosis were enrolled, which accounted for a mean of 3.2% (95% confidence interval: 2.4-4.2%) of yearly HIV infection admissions among patients from eastern China. Symptoms included fever, cough, and gastrointestinal complaints, whereas the most common sign was skin lesions. Anemia occurred in 87.5% (42/48) of the patients. The overall mortality rate was 16.7%. Low CD4 T-cell count and hemoglobin level were correlated with mortality. Based on these results, we concluded that penicilliosis should be considered in HIV-infected patients from eastern China who present with fever, cutaneous lesions, and anemia. The clinical characters and the prognosis of patients with penicilliosis are similar to those in endemic areas. More attention should be paid to penicilliosis patients with low CD4 T-cell count and/or low hemoglobin level.

Antiretroviral drugs saquinavir and ritonavir reduce inhibitory concentration values of itraconazole against Histoplasma capsulatum strains in vitro

Recent studies have shown that some drugs that are not routinely used to treat fungal infections have antifungal activity, such as protease inhibitor antiretroviral drugs. This study investigated the in vitro susceptibility of Histoplasma capsulatum var. capsulatum to saquinavir and ritonavir, and its combination with the antifungal itraconazole. The susceptibility assay was performed according to Clinical and Laboratory Standards Institute guidelines. All strains were inhibited by the protease inhibitor antiretroviral drugs. Saquinavir showed minimum inhibitory concentrations ranging from 0.125 to 1μgmL(-1) for both phases, and ritonavir presented minimum inhibitory concentrations ranging from 0.0312 to 4μgmL(-1)and from 0.0625 to 1μgmL(-1) for filamentous and yeast phase, respectively. Concerning the antifungal itraconazole, the minimum inhibitory concentration values ranged from 0.0019 to 0.125μgmL(-1) and from 0.0039 to 0.0312μgmL(-1) for the filamentous and yeast phase, respectively. The combination of saquinavir or ritonavir with itraconazole was synergistic against H. capsulatum, with a significant reduction in the minimum inhibitory concentrations of both drugs against the strains (p<0.05). These data show an important in vitro synergy between protease inhibitors and itraconazole against the fungus H. capsulatum.

Metronidazole or Cotrimoxazole therapy is associated with a decrease in intestinal bioavailability of common antiretroviral drugs

Metronidazole (MTZ) and Cotrimoxazole (CTX) are used in HIV/AIDS patients eligible for antiretroviral treatment. The objective of this animal study was to determine whether pre-treatment with antibiotics affects the intestinal bioavailability of Atazanavir (ATV) and Ritonavir (RTV). After oral administration of 1 mg MTZ and CTX for 7 days, the rat colonic mucosa were analyzed for mucus thickness or placed in Ussing chambers to measure ATV and RTV net transepithelial fluxes (J_net). 1. In control rats, the mucus thickness was 43.3±7.6 µm and 40.7±6.9 µm, in proximal and distal colon, respectively. In proximal colon, the thickness was 57.2±8.8 and 58.2±6.9 µm after MTZ and CTX, respectively whereas in distal colon, the thickness was 121.1±38.4 and 170.5±35.0 µm (P<0.05) respectively. 2. Transepithelial conductance was reduced after MTZ or CTX in the proximal and distal colon. 3. In control, net ATV secretion was observed both in proximal (−0.36±0.02 µg.hr⁻¹ cm⁻²) and distal colon (−0.30±0.08 µg.hr⁻¹ cm⁻²). After MTZ and CTX, it was increased in the proximal colon by two 2 fold and 4 fold, respectively and in the distal colon by 3 fold and 5 fold, respectively. 4. In control, there was no net active RTV transport either in proximal (+0.01±0.01 µg.hr⁻¹ cm⁻²) or distal colon (+0.04±0.01 µg.hr⁻¹ cm⁻²). After MTZ and CTX, secretion was increased 5 fold and 10 fold, respectively, in the proximal colon and two fold and 5 fold, respectively in the distal colon (p<0.001). In conclusion, after MTZ and CTX therapy, the mucus layer was enlarged, passive permeability was decreased and ATV and RTV were actively secreted by the colonic epithelium suggesting that, in rat, the intestinal bioavailability of ATV and RTV is impaired after antibiotic therapy.

Disseminated histoplasmosis in HIV-infected patients: determinants of relapse and mortality in a north-eastern area of Brazil

Many relapses and deaths resulting from disseminated histoplasmosis (DH) in acquired immunodeficiency syndrome (AIDS) patients have been observed in an endemic area in north-eastern Brazil. The objective of this study was to evaluate the risk factors associated with the clinical outcomes of DH/AIDS coinfection in patients from the state of Ceará, Brazil. A retrospective cohort of AIDS patients, after their hospital discharge due to first DH episode in the period 2002-2008, was followed until December 31, 2010, to investigate the factors associated with relapse and mortality. A total of 145 patients were evaluated in the study. Thirty patients (23.3%) relapsed and the overall mortality was 30.2%. The following variables were significantly (P < 0.05) associated with relapse and overall mortality (univariate analysis): non-adherence to highly active antiretroviral therapy (HAART), irregular use of an antifungal, non-recovery of the CD4+ count and having AIDS before DH; histoplasmosis relapse was also significantly associated with mortality. In the multivariate analysis, non-adherence to HAART was the independent risk factor that was associated with both relapse (Adj OR = 6.28) and overall mortality (Adj OR = 8.03); efavirenz usage was discovered to be significant only for the overall mortality rate (Adj OR = 4.50). Adherence to HAART was the most important variable that influenced the outcomes in this specific population.

Itraconazole: an update on pharmacology and clinical use for treatment of invasive and allergic fungal infections

INTRODUCTION

Fungal infections are a major source of global morbidity and mortality. Itraconazole is a triazole antifungal agent that is widely used for the prevention and treatment of fungal infection. While newer antifungal agents are now available, itraconazole is an orally bioavailable agent with broad-spectrum antifungal activity. Itraconazole remains a useful drug for the management of allergic and invasive mycoses worldwide.

AREAS COVERED

This article provides a summary of the pharmacokinetics, pharmacodynamics and clinical uses of itraconazole. Additionally, the authors summarise the safety and recently described toxicodynamics and discuss the value of therapeutic drug monitoring (TDM) with itraconazole. The following search criteria were constructed in order to identify relevant literature using PubMed and Ovid-MEDLINE: itraconazole, triazole, pharmacokinetics, pharmacodynamics, toxicodynamics and TDM. Relevant abstracts and articles identified from reviewing secondary citations were additionally retrieved and included if relevant.

EXPERT OPINION

Itraconazole remains an important agent in the prevention and treatment of fungal infection. Itraconazole has a broad-spectrum of activity and is available in both an intravenous and oral form making long-term use in chronic mycoses practical. Itraconazole is widely used for the treatment of endemic fungal infections. Pharmacokinetic variability and clinically important drug interactions make TDM of itraconazole an important consideration.

Systemic mycoses in immunodepressed patients (AIDS)

Infectious and noninfectious skin diseases are observed in about 90% of HIV patients, and their incidence increases and is more severe as the immune system weakens. Cutaneous manifestations are considered good clinical predictors for the immunological condition of the patient with AIDS and the introduction of highly effective antiretroviral therapy totally changed the prognosis of the mycoses, among other diseases associated with AIDS, permitting longer survival and acceptable level of quality of life for these patients. This contribution describes the systemic mycoses that are more frequent in the seropositive population, that is, patients with HIV/AIDS, which are cryptococcosis, histoplasmosis, coccidioidomycosis, blastomycosis, paracoccidioidomycosis, sporotrichosis, penicilliosis, and aspergillosis. Their causative agents, mode of transmission, clinics, laboratorial diagnosis and therapy, in the aspects related to immunodepressed patients, are reviewed.

Antiretroviral drug interactions: overview of interactions involving new and investigational agents and the role of therapeutic drug monitoring for management

Antiretrovirals are prone to drug-drug and drug-food interactions that can result in subtherapeutic or supratherapeutic concentrations. Interactions between antiretrovirals and medications for other diseases are common due to shared metabolism through cytochrome P450 (CYP450) and uridine diphosphate glucuronosyltransferase (UGT) enzymes and transport by membrane proteins (e.g., p-glycoprotein, organic anion-transporting polypeptide). The clinical significance of antiretroviral drug interactions is reviewed, with a focus on new and investigational agents. An overview of the mechanistic basis for drug interactions and the effect of individual antiretrovirals on CYP450 and UGT isoforms are provided. Interactions between antiretrovirals and medications for other co-morbidities are summarized. The role of therapeutic drug monitoring in the detection and management of antiretroviral drug interactions is also briefly discussed.

Interactions between antifungal and antiretroviral agents

IMPORTANCE OF THE FIELD

Since the advent of combination antiretroviral therapy, the incidence of opportunistic infections has declined and the life expectancy of HIV-infected people has significantly increased. However, opportunistic infections, including fungal diseases, remain a leading cause of hospitalizations and mortality in HIV-infected people. With the availability of several new antiretroviral and antifungal agents, drug-drug interactions emerge as a potential safety concern.

AREAS COVERED IN THIS REVIEW

Relevant literature was identified using a Medline search of articles published up to March 2010 and a review of conference abstracts. Search terms included HIV, antifungal agents and drug interactions. Original papers and relevant citations were considered for this review.

WHAT THE READER WILL GAIN

Readers will gain an understanding of the pharmacokinetic properties of antiretroviral and antifungal agents, and insight into significant drug-drug interactions which may require dosage adjustments or a change in therapy.

TAKE HOME MESSAGE

Azole antifungal drugs, with the exception of fluconazole, pose the greatest risk of two-way interactions with antiretroviral drugs through CYP450 enzymes effects. Limited studies suggest the risk of interactions between antiretroviral drugs and echinocandins is much lower. The combination of tenofovir and amphotericin B should be used with caution and close monitoring of renal function is required.

Effects of cytochrome P450 3A (CYP3A) and the drug transporters P-glycoprotein (MDR1/ABCB1) and MRP2 (ABCC2) on the pharmacokinetics of lopinavir

BACKGROUND AND PURPOSE

Lopinavir is extensively metabolized by cytochrome P450 3A (CYP3A) and is considered to be a substrate for the drug transporters ABCB1 (P-glycoprotein) and ABCC2 (MRP2). Here, we have assessed the individual and combined effects of CYP3A, ABCB1 and ABCC2 on the pharmacokinetics of lopinavir and the relative importance of intestinal and hepatic metabolism. We also evaluated whether ritonavir increases lopinavir oral bioavailability by inhibition of CYP3A, ABCB1 and/or ABCC2.

EXPERIMENTAL APPROACH

Lopinavir transport was measured in Madin-Darby canine kidney cells expressing ABCB1 or ABCC2. Oral lopinavir kinetics (+/- ritonavir) was studied in mice with genetic deletions of Cyp3a, Abcb1a/b and/or Abcc2, or in transgenic mice expressing human CYP3A4 exclusively in the liver and/or intestine.

KEY RESULTS

Lopinavir was transported by ABCB1 but not by ABCC2 in vitro. Lopinavir area under the plasma concentration - time curve (AUC)(oral) was increased in Abcb1a/b(-/-) mice (approximately ninefold vs. wild-type) but not in Abcc2(-/-) mice. Increased lopinavir AUC(oral) (>2000-fold) was observed in cytochrome P450 3A knockout (Cyp3a(-/-)) mice compared with wild-type mice. No difference in AUC(oral) between Cyp3a(-/-) and Cyp3a/Abcb1a/b/Abcc2(-/-) mice was observed. CYP3A4 activity in intestine or liver, separately, reduced lopinavir AUC(oral) (>100-fold), compared with Cyp3a(-/-) mice. Ritonavir markedly increased lopinavir AUC(oral) in all CYP3A-containing mouse strains.

CONCLUSIONS AND IMPLICATIONS

CYP3A was the major determinant of lopinavir pharmacokinetics, far more than Abcb1a/b. Both intestinal and hepatic CYP3A activity contributed importantly to low oral bioavailability of lopinavir. Ritonavir increased lopinavir bioavailability primarily by inhibiting CYP3A. Effects of Abcb1a/b were only detectable in the presence of CYP3A, suggesting saturation of Abcb1a/b in the absence of CYP3A activity.

In vitro activity of isavuconazole against 140 reference fungal strains and 165 clinically isolated yeasts from Japan

The in vitro susceptibilities of 140 laboratory reference strains of fungi, including type strains, and 165 clinical yeast isolates from Japan towards isavuconazole compared with fluconazole (FLC), itraconazole (ITC), voriconazole and amphotericin B were measured. Broth microdilution methods based on Clinical and Laboratory Standards Institute (CLSI) methods were used for yeasts, and RPMI-MOPS medium semi-solidified with 0.2% low-melting-point agarose based on CLSI guidelines was used for moulds. The range of isavuconazole minimum inhibitory concentrations (MICs) was 0.0004-0.21 mg/L for Candida albicans, 0.0036-0.4 mg/L for Candida glabrata, 0.023-0.058 mg/L for Candida krusei, 0.0026-0.032 mg/L for Cryptococcus neoformans, 0.1-0.39mg/L for Aspergillus fumigatus and 0.2-0.39 mg/L for Aspergillus terreus. Isavuconazole was as active as ITC against the dimorphic true pathogenic fungi, with a range of MICs from <0.0004 mg/L to 0.0063 mg/L for Blastomyces dermatitidis and Histoplasma capsulatum. It was also active against uncommon dematiaceous fungi such as Exophiala spp. and Phialophora spp. as well as against dermatophytic species. Isavuconazole showed very good in vitro antifungal activity with a broad spectrum, including against FLC-resistant Candida spp., Aspergillus spp. and uncommon opportunistic fungal species. This is the first report of the in vitro susceptibility of Japanese clinical yeast isolates to isavuconazole. No cross-resistance was found to isavuconazole amongst FLC-resistant strains.

Drug-Drug Interaction Between Itraconazole and the Protease Inhibitor Lopinavir/Ritonavir

Objective:

To report the results of therapeutic drug monitoring of lopinavir/ritonavir and itraconazole concentrations in an HIV-infected male who was treated for histoplasmosis.

Case Summary:

A 34-year-old HIV-infected man who had recently initiated efavirenz-based antiretroviral therapy was diagnosed with disseminated Histoplasma capsulatum infection. In the hospital, lopinavir/ritonavir 400 mg/100 mg twice daily replaced efavirenz to avoid etavirenz-itraconazole interactions. After 14 days of liposomal amphotericin B therapy, itraconazole solution was initiated at 150 mg twice daily for 3 days, followed by 200 mg daily. Prior to itraconazole initiation, lopinavir trough concentration was 7.4 mg/L. The lopinavir trough concentration 15 days later, after 14 days of itraconazole, was 6.8 mg/L. An itraconazole concentration measured 2 hours post-dose on day 15 of oral therapy was 1.9 pg/mL. After 2 weeks of liposomal amphotericin, urine Histoplasma antigen was 27.23 ng/mL; after 5 months of oral itraconazole therapy, it decreased to 5.24 ng/mL. Plasma HIV RNA decreased 4.26 log10 in 5 months to less than 40 copies/mL The patient has demonstrated marked clinical improvement.

Discussion:

In this case, dosing recommendations of itraconazole 200 mg daily with lopinavir/ritonavir were appropriate. Lopinavir trough concentrations were not significantly different following the addition of itraconazole and were above the minimum target of 1 mg/L in treatment-naive patients. The itraconazole concentration was above the recommended concentration of at least 1 μg/mL.

Conclusions:

The dose of itraconazole was reduced to 200 mg daily as recommended by current guidelines, and therapeutic drug monitoring of both itraconazole and lopinavir concentrations confirmed that no further dosage adjustments were necessary.

Clinical Evidence of Interaction Between Itraconazole and Nonnucleoside Reverse Transcriptase Inhibitors in HIV-Infected Patients with Disseminated Histoplasmosis

Background

Itraconazole is the preferred drug for chronic maintenance therapy in HIV-infected patients with disseminated histoplasmosis. Unfortunately, few clinical data exist confirming a presumed interaction between itraconazole and nonnucleoside reverse transcriptase inhibitors (NNRTIs).

Objective

To determine whether serum itraconazole concentrations are affected by the type of antiretroviral therapy (NNRTI or protease inhibitor [PI]) being taken concomitantly.

Methods

This retrospective cohort identified patients on antiretroviral therapy and itraconazole for disseminated histoplasmosis between January 2003 and December 2006 at a large HIV clinic in Houston, TX. Available laboratory values were abstracted from medical records.

Results

Thirteen itraconazole concentrations from 10 patients were avaitable for analysis: 7 patients were on concomitant Pls, 4 on concomitant NNRTIs, and 2 on antiretroviral regimens containing both Pls and NNRTIs. Six of the itraconazole concentrations during concomitant PI treatment were therapeutic (>1.0 μg/mL). in contrast with none in patients taking an NNRTI. All patients taking concomitant NNRTIs had undetectable serum itraconazole concentrations (<0.05 μg/mL). Two patients switched from NNRTI-based to PI-based antiretroviral regimens and subsequently reached therapeutic itraconazole concentrations. Although limited by small sample size, this study provides the largest clinical data among HIV-infected patients demonstrating that coadministration of an NNRTI and itraconazole results in significant decreases in itraconazole blood concentrations, likely by inducing the CYP3A4 enzyme system.

Conclusions

Itraconazole concentrations should be monitored in patients taking concomitant NNRTIs. PI-based highly active antiretroviral therapy (HAART) may be preferred over NNRTI-based HAART when itraconazole is used to treat HIV-infected patients with disseminated histoplasmosis.

Long-term pharmacokinetic efficacy and safety of low-dose ritonavir as a booster and atazanavir pharmaceutical formulation based on solid dispersion system in rats

Atazanavir (ATV) is clinically coadministered with low-dose ritonavir (RTV), which boosts the oral bioavailability (BA) of ATV by inhibiting cytochrome P450 (CYP) 3A, and P-glycoprotein (Pgp) via the same metabolic pathway; however, it is well known that in the chronic phase, the inhibition effect of RTV on Pgp and CYP3A becomes an induction effect. In this study, we investigated the long-term efficacy and safety of RTV-boosted ATV in rats with a clinical relevant dosage of ATV and RTV, 7 mg/kg and 2 mg/kg, respectively, and drew a direct comparison with RTV-boosted ATV and the previously reported ATV pharmaceutical formulation based on a solid dispersion system (ATV-SLS SD+G). Rats received RTV-boosted ATV or ATV-SLS SD+G for 14 d in the pharmacokinetic study. In addition, after 14-d repeated administration of each formulation, cyclosporine A (CyA) was administered to rats and Western blot analysis of Pgp and CYP3A was performed to investigate the impact on pharmacokinetic interaction of each ATV formulation. After repeated administration of both formulations, there was no significant difference between ATV pharmacokinetic parameters on day 1 and 14; therefore, it was considered that the long-term efficacy of both ATV formulations was maintained. However, after treatment with RTV-boosted ATV, the Cmax and AUC0-infinity of the following CyA significantly decreased to 49% and 47% in comparison to the control, respectively, and the Pgp expression in the small intestine by Western blot analysis was approximately 2-fold higher than the control, whereas after treatment with ATV pharmaceutical formulation, neither significant alteration of CyA nor notable change in the expression of intestinal Pgp and hepatic CYP3A was observed. Therefore, it was considered that the BA of CyA after treatment with RTV-boosted ATV would decrease by the induction effect of RTV in chronic phase as described above. The results of this study revealed that the chronic use of low-dose RTV as a booster has great potential to compromise drug-drug interactions; therefore, it is recommended that the BA of protease inhibitors be improved by a pharmaceutical approach without pharmacokinetic interaction by RTV.

Drug-drug interaction between itraconazole and efavirenz in a patient with AIDS and disseminated histoplasmosis

Although there is a presumed drug-drug interaction between itraconazole and nonnucleoside reverse-transcriptase inhibitors, the medical literature lacks such documentation. We describe a drug-drug interaction between itraconazole and efavirenz in a patient with disseminated histoplasmosis and acquired immunodeficiency syndrome (AIDS). The drug combination resulted in persistently elevated urinary Histoplasma antigen levels and subtherapeutic plasma itraconazole concentrations. Changing treatment from efavirenz to a protease inhibitor was accompanied by improvements in the desired urinary Histoplasma antigen level and plasma itraconazole concentration.

Mechanisms of Pharmacokinetic and Pharmacodynamic Drug Interactions Associated with Ritonavir-Enhanced Tipranavir

Tipranavir is a nonpeptidic protease inhibitor that has activity against human immunodeficiency virus strains resistant to multiple protease inhibitors. Tipranavir 500 mg is coadministered with ritonavir 200 mg. Tipranavir is metabolized by cytochrome P450 (CYP) 3A and, when combined with ritonavir in vitro, causes inhibition of CYP1A2, CYP2C9, CYP2C19, CYP2D6, and CYP3A in addition to induction of glucuronidase and the drug transporter P-glycoprotein. As a result, drug-drug interactions between tipranavir-ritonavir and other coadministered drugs are a concern. In addition to interactions with other antiretrovirals, tipranavir-ritonavir interactions with antifungals, antimycobacterials, oral contraceptives, statins, and antidiarrheals have been specifically evaluated. For other drugs such as antiarrhythmics, antihistamines, ergot derivatives, selective serotonin receptor agonists (or triptans), gastrointestinal motility agents, erectile dysfunction agents, and calcium channel blockers, interactions can be predicted based on studies with other ritonavir-boosted protease inhibitors and what is known about tipranavir-ritonavir CYP and P-glycoprotein utilization. The highly complex nature of drug interactions dictates that cautious prescribing should occur with narrow-therapeutic-index drugs that have not been specifically studied. Thus, the known interaction potential of tipranavir-ritonavir is reported, and in vitro and in vivo data are provided to assist clinicians in predicting interactions not yet studied. As more clinical interaction data are generated, better insight will be gained into the specific mechanisms of interactions with tipranavir-ritonavir.

Cushing syndrome and severe adrenal suppression caused by fluticasone and protease inhibitor combination in an HIV-infected adolescent

A 14-year-old female with perinatally acquired HIV on boosted protease inhibitor (PI) therapy with atazanavir and ritonavir rapidly developed cushingoid features with excessive weight gain and moon facies within 2 weeks of receiving inhaled fluticasone/salmeterol for asthma treatment. Soon after discontinuing PIs and inhaled steroid, she required hospitalization for dyspnea, headache, muscle weakness, and extreme fatigue requiring hydrocortisone replacement therapy for presumed adrenal insufficiency. Cushing syndrome and adrenal suppression were very likely caused by elevated steroid systemic concentrations resulting from the cytochrome p450 interaction between the protease inhibitors and fluticasone. The Naranjo probability scale score of 5 suggests that the event was probably drug related. This is the first case report of fluticasone and PI-induced Cushing syndrome and adrenal suppression in a pediatric patient without a history of recent or concomitant treatment with systemic steroid therapy. Additionally, this case is unique as it is the most rapid (<2 weeks) presentation documented, thus far. Health care professionals should be conscious of this important drug-drug interaction in HIV-infected children and adolescents and be aware that rapid onset of hypercortisolism and adrenal suppression are possible.

Coccidioidomycosis in persons infected with HIV-1

Coccidioidomycosis is a recognized opportunistic infection in those with HIV-1 infection. The major risk factor is immunodeficiency, particularly when the peripheral blood CD4 T lymphocyte count is below 250/muL. There are many manifestations of coccidioidomycosis during HIV-1 infection, including diffuse, reticulonodular pneumonia, focal primary pneumonia, and disease disseminated beyond the thoracic cavity. Diagnosis is based on serology, culture and histopathologic identification. Two therapeutic modalities are currently available, the polyene antifungal amphotericin B and the triazole antifungals. Of the latter, the most experience is with the triazoles fluconazole and itraconazole. There are increasing data regarding drug interactions between triazoles and antiretroviral agents. The duration of treatment of coccidioidomycosis in those with HIV-1 infection is not established and in many patients it is either prolonged or life-long. Adherence to antiretroviral therapy is important in preventing recurrence.

Pharmaceutical Approach to HIV Protease Inhibitor Atazanavir for Bioavailability Enhancement Based on Solid Dispersion System

Atazanavir (ATV) is a low oral bioavailability (BA) compound and, clinically, is generally coadministrated with ritonavir (RTV), which boosts the oral BA of ATV by inhibiting cytochrome P450 (CYP) 3A, and P-glycoprotein (Pgp) via the same metabolic pathway. However, depending on pharmacokinetic interaction, RTV-boosted ATV has great potential for other comedication. In this study we demonstrated the pharmaceutical approach to BA improvement of ATV without RTV in rats, based on the solid dispersion system using sodium lauryl sulfate (SLS) as a carrier and Gelucire 50/13 as an absorption enhancer. ATV solid dispersions in SLS were prepared by a conventional solvent method and, at ratios of ATV to SLS of 1 : 2 and 1 : 3, were demonstrated to form an amorphous state in powder X-ray diffraction (PXRD) analysis and exhibited 2.26- and 2.36-fold improvement in a dissolution test in comparison to bulk ATV, respectively. After oral administration to rats, ATV solid dispersion in SLS at a ratio of 1 : 2 showed a 3.5-fold increase in BA compared with bulk ATV. Moreover, the addition of Gelucire 50/13 to ATV solid dispersion, at a total ratio of Gelucire 50/13, ATV and SLS 1 : 1 : 2 gave 7.0- and 4.7-fold increase in Cmax and BA compared with bulk ATV, respectively, when the relative BA to RTV-boosted ATV reached 93%. The results in this study proved that a pharmaceutical approach could improve the bioavailability of ATV without pharmacokinetic interaction with RTV.

Population pharmacokinetics of lopinavir in combination with ritonavir in HIV-1-infected patients

AIMS

To develop a population pharmacokinetic model for lopinavir in combination with ritonavir, in which the interaction between both drugs was characterized, and in which relationships between patient characteristics and pharmacokinetics were identified.

METHODS

The pharmacokinetics of lopinavir in combination with ritonavir were described using NONMEM (version V, level 1.1). First, ritonavir data were fitted to a previously developed model to obtain individual Bayesian estimates of pharmacokinetic parameters. Hereafter, an integrated model for the description of the pharmacokinetics of lopinavir with ritonavir was designed.

RESULTS

From 122 outpatients 748 lopinavir and 748 ritonavir plasma concentrations were available for analysis. The interaction between the drugs was described by a time-independent inverse relationship between the exposure to ritonavir over a dosing-interval and the apparent clearance (CL/F) of lopinavir. The model parameters volume of distribution and absorption rate constant were 61.6 l (95% prediction interval (PI) 22.4, 83.7) and 0.564 h(-1) (95% PI 0.208, 0.947), respectively. The model yielded a theoretical value for the CL/F of lopinavir without ritonavir of 14.8 l h(-1) (95%PI 12.1, 20.1), which translates to a value of 5.73 l h(-1) in the presence of ritonavir. The only factor with significant effect on the pharmacokinetics was concurrent use of non-nucleoside reverse transcriptase inhibitors (NNRTI), which increased the CL/F of lopinavir by 39% (P < 0.001).

CONCLUSIONS

We have developed a model that has defined a time-independent inverse relationship between the exposure to ritonavir and the CL/F of lopinavir, and provided an adequate description of the pharmacokinetic parameters for the latter. Concomitant use of the NNRTIs efavirenz and nevirapine increased the CL/F of lopinavir.

Disseminated histoplasmosis: case report and brief review

Disseminated Histoplasmosis is a severe and often-fatal opportunistic infection when left untreated among patients with AIDS. Occurring in 3-5 percent of patients with AIDS living in the areas of endemicity, this infection should be suspected in patients with a CD4 cell count of <150 cells/microL presenting with non-specific clinical signs such as fever, weight loss, and lymphadenopathy. We report our experience to increase awareness of the clinical spectrum of disseminated histoplasmosis and its similarity to other infections and malignancies and update the reader on recommended therapeutic modalities.

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.