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Sporanox Oral Solution

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Sporanox Oral Solution

Sporanox Oral Solution

CLINICAL PHARMACOLOGY

Pharmacokinetics and Metabolism

NOTE: The plasma concentrations reported below were measured by high-performance liquid chromatography (HPLC) specific for itraconazole. When itraconazole in plasma is measured by a bioassay, values reported may be higher than those obtained by HPLC due to the presence of the bioactive metabolite, hydroxyitraconazole. (See Microbiology.)

The absolute bioavailability of itraconazole administered as a non-marketed solution formulation under fed conditions was 55% in 6 healthy male volunteers. However, the bioavailability of SPORANOX® (itraconazole) Oral Solution is increased under fasted conditions reaching higher maximum plasma concentrations (Cmax) in a shorter period of time. In 27 healthy male volunteers, the steady-state area under the plasma concentration versus time curve (AUC0-24h) of itraconazole (SPORANOX® Oral Solution, 200 mg daily for 15 days) under fasted conditions was 131 ± 30% of that obtained under fed conditions. Therefore, unlike SPORANOX® Capsules, it is recommended that SPORANOX® Oral Solution be administered without food. Presented in the table below are the steady-state (Day 15) pharmacokinetic parameters for itraconazole and hydroxyitraconazole (SPORANOX®Oral Solution) under fasted and fed conditions:

  Itraconazole Hydroxyitraconazole
Fasted Fed Fasted Fed
Cmax (ng/mL) 1963 ± 601* 1435 ± 477 2055 ± 487 1781 ± 397
Tmax (hours) 2.5 ± 0.8 4.4 ± 0.7 5.3 ± 4.3 4.3 ± 1.2
AUC0-24h (ng•h/mL) 29271 ± 10285 22815 ± 7098 45184 ± 10981 38823 ± 8907
t½ (hours) 39.7 ± 13 37.4 ± 13 27.3 ± 13 26.1 ± 10
* mean ± standard deviation

The bioavailability of SPORANOX® Oral Solution relative to SPORANOX® Capsules was studied in 30 healthy male volunteers who received 200 mg of itraconazole as the oral solution and capsules under fed conditions. The AUC0-∞ from SPORANOX® Oral Solution was 149 ± 68% of that obtained from SPORANOX® Capsules; a similar increase was observed for hydroxyitraconazole. In addition, a cross study comparison of itraconazole and hydroxyitraconazole pharmacokinetics following the administration of single 200 mg doses of SPORANOX® Oral Solution (under fasted conditions) or SPORANOX® Capsules (under fed conditions) indicates that when these two formulations are administered under conditions which optimize their systemic absorption, the bioavailability of the solution relative to capsules is expected to be increased further. Therefore, it is recommended that SPORANOX® Oral Solution and SPORANOX® Capsules not be used interchangeably. The following table contains pharmacokinetic parameters for itraconazole and hydroxyitraconazole following single 200 mg doses of SPORANOX® Oral Solution (n=27) or SPORANOX® Capsules (n=30) administered to healthy male volunteers under fasted and fed conditions, respectively:

  Itraconazole Hydroxyitraconazole
Oral Solution fasted Capsules fed Oral Solution fasted Capsules fed
Cmax (ng/mL) 544 ± 213* 302 ± 119 622 ± 116 504 ± 132
Tmax (hours) 2.2 ± 0.8 5 ± 0.8 3.5 ± 1.2 5 ± 1
AUC0-24h (ng•h/mL) 4505 ± 1670 2682 ± 1084 9552 ± 1835 7293 ± 2144
* mean ± standard deviation

The plasma protein binding of itraconazole is 99.8% and that of hydroxyitraconazole is 99.5%. Following intravenous administration, the volume of distribution of itraconazole averaged 796 ± 185 L.

Itraconazole is metabolized predominately by the cytochrome P450 3A4 isoenzyme system (CYP3A4), resulting in the formation of several metabolites, including hydroxyitraconazole, the major metabolite. Results of a pharmacokinetics study suggest that itraconazole may undergo saturable metabolism with multiple dosing. Fecal excretion of the parent drug varies between 3-18% of the dose. Renal excretion of the parent drug is less than 0.03% of the dose. About 40% of the dose is excreted as inactive metabolites in the urine. No single excreted metabolite represents more than 5% of a dose. Itraconazole total plasma clearance averaged 381 ± 95 mL/minute following intravenous administration. (See CONTRAINDICATIONS and PRECAUTIONS: DRUG INTERACTIONS for more information.)

Special Populations

Pediatrics

The pharmacokinetics of SPORANOX® Oral Solution were studied in 26 pediatric patients requiring systemic antifungal therapy. Patients were stratified by age: 6 months to 2 years (n=8), 2 to 5 years (n=7) and 5 to 12 years (n=11), and received itraconazole oral solution 5 mg/kg once daily for 14 days. Pharmacokinetic parameters at steady-state (Day 14) were not significantly different among the age strata and are summarized in the table below for all 26 patients:

  Itraconazole Hydroxyitraconazole
Cmax (ng/mL) 582.5 ± 382.4* 692.4 ± 355.0
Cmin (ng/mL) 187.5 ± 161.4 403.8 ± 336.1
AUC0-24h (ng•h/mL) 7706.7 ± 5245.2 13356.4 ± 8942.4
t½ (hours) 35.8 ± 35.6 17.7 ± 13.0
* mean ± standard deviation

Renal Insufficiency

Limited data are available on the use of oral itraconazole in patients with renal impairment. A pharmacokinetic study using a single 200-mg dose of itraconazole (four 50-mg capsules) was conducted in three groups of patients with renal impairment (uremia: n=7; hemodialysis: n=7; and continuous ambulatory peritoneal dialysis: n=5). In uremic subjects with a mean creatinine clearance of 13 mL/min. 1.73 m², the exposure, based on AUC, was slightly reduced compared with normal population parameters. This study did not demonstrate any significant effect of hemodialysis or continuous ambulatory peritoneal dialysis on the pharmacokinetics of itraconazole (Tmax, Cmax, and AUC0-8). Plasma concentration-versus-time profiles showed wide intersubject variation in all three groups. Caution should be exercised when the drug is administered in this patient population. (See PRECAUTIONS and DOSAGE AND ADMINISTRATION.)

Hepatic Insufficiency

Itraconazole is predominantly metabolized in the liver. Patients with impaired hepatic function should be carefully monitored when taking itraconazole. A pharmacokinetic study using a single oral 100 mg capsule dose of itraconazole was conducted in 6 healthy and 12 cirrhotic subjects. A statistically significant reduction in mean Cmax (47%) and a twofold increase in the elimination half-life (37 ± 17 hours vs. 16 ± 5 hours) of itraconazole were noted in cirrhotic subjects compared with healthy subjects. However, overall exposure to itraconazole, based on AUC, was similar in cirrhotic patients and in healthy subjects. The prolonged elimination half-life of itraconazole observed in the single oral dose clinical trial with itraconazole capsules in cirrhotic patients should be considered when deciding to initiate therapy with other medications metabolized by CYP3A4. Data are not available in cirrhotic patients during long-term use of itraconazole. (See BOX WARNING, CONTRAINDICATIONS, PRECAUTIONS: DRUG INTERACTIONS and DOSAGE AND ADMINISTRATION.)

Decreased Cardiac Contractility

When itraconazole was administered intravenously to anesthetized dogs, a dose-related negative inotropic effect was documented. In a healthy volunteer study of itraconazole intravenous infusion, transient, asymptomatic decreases in left ventricular ejection fraction were observed using gated SPECT imaging; these resolved before the next infusion, 12 hours later. If signs or symptoms of congestive heart failure appear during administration of SPORANOX® Oral Solution, monitor carefully and consider other treatment alternatives which may include discontinuation of SPORANOX® Oral Solution administration. (See WARNINGS, PRECAUTIONS: DRUG INTERACTIONS and ADVERSE REACTIONS: Post-marketing Experience for more information.)

Cystic Fibrosis

Seventeen cystic fibrosis patients, ages 7 to 28 years old, were administered itraconazole oral solution 2.5 mg/kg b.i.d. for 14 days in a pharmacokinetic study. Sixteen patients completed the study. Steady state trough concentrations > 250 ng/mL were achieved in 6 out of 11 patients ≥ 16 years of age but in none of the 5 patients < 16 years of age. Large variability was observed in the pharmacokinetic data (%CV for trough concentrations = 98% and 70% for ≥ 16 and < 16 years, respectively; %CV for AUC = 75% and 58% for ≥ 16 and < 16 years, respectively). If a patient with cystic fibrosis does not respond to SPORANOX® Oral Solution, consideration should be given to switching to alternative therapy.

Microbiology

Mechanism of Action

In vitro studies have demonstrated that itraconazole inhibits the cytochrome P450-dependent synthesis of ergosterol, which is a vital component of fungal cell membranes.

Activity In Vitro and In Vivo

Itraconazole has been shown to be active against most strains of the following microorganisms, both in vitro and in clinical infections.

Aspergillus flavus
Aspergillus fumigatus

Blastomyces dermatitidis

Candida albicans

Histoplasma capsulatum

Histoplasma duboisii

Susceptibility Testing Methods

(Applicable to Candida isolates from patients with oropharyngeal or esophageal candidiasis)

Candida albicans

The interpretive criteria and breakpoints for itraconazole against Candida albicans are applicable to tests performed using Clinical Laboratory and Standards Institute (CLSI) microbroth dilution reference method M27A for MIC (partial inhibition endpoint) read at 48 hours.

Broth Microdilution Techniques

Quantitative methods are used to determine antifungal minimum inhibitory concentrations (MICs). These MICs provide estimates of the susceptibility of Candida spp. to antifungal agents. MICs should be determined using a standardized procedure at 48 hours. Standardized procedures are based on a microdilution method (broth) with standardized inoculum concentrations and standardized concentrations of itraconazole powder. The MIC values should be interpreted according to the criteria provided in Table below:

Susceptibility Interpretive Criteria for Itraconazole

Pathogen Broth Microdilution MIC* (μg/mL) at 48 Hours
S I R
Candida albicans ≤ 0.125 0.25 – 0.5 ≥ 1
* A report of “Susceptible” indicates that the pathogen is likely to be inhibited if the antimicrobial compound in the blood reaches the concentrations usually achievable. The intermediate category implies that an infection due to the isolate may be appropriately treated in the body sites where the drugs are physiologically concentrated or when a high dosage of drug is used. The resistant category implies that isolates are not inhibited by the usually achievable concentrations of the agent with normal dosage schedules and clinical efficacy of the agent against the isolate has not been reliably shown in treatment studies. The intermediate category is sometimes called Susceptible-Dose Dependent (SDD) and both categories are equivalent for itraconazole.

Quality Control

Standardized susceptibility test procedures require the use of quality control organisms to control the technical aspects of the test procedures. Standard itraconazole powder should provide the following range of values noted in the table below.

NOTE: Quality control microorganisms are specific strains of organisms with intrinsic biological properties relating to resistance mechanisms and their genetic expression within fungi; the specific strains used for microbiological control are not clinically significant.

Acceptable Quality Control Ranges for Itraconazole to be used in Validation of Susceptibility Test Results†

QC Strain Broth Microdilution MIC (?g/mL) at 48 Hours
Candida parapsilosis ATCC† 22019 0.06-0.25
Candida krusei ATCC 6258 0.12-0.5
† ATCC is the registered trademark of the American Type Culture Collection.

Activity in Animal Models

Itraconazole administered orally was active in a variety of animal models of fungal infection using standard laboratory strains of fungi. Fungistatic activity has been demonstrated against disseminated fungal infections caused by Blastomyces dermatitidis, Histoplasma duboisii, Aspergillus fumigatus, Coccidioides immitis, Cryptococcus neoformans, Paracoccidioides brasiliensis, Sporothrix schenckii, Trichophyton rubrum, and Trichophyton mentagrophytes.

Itraconazole administered at 2.5 mg/kg and 5 mg/kg via the oral and parenteral routes increased survival rates and sterilized organ systems in normal and immunosuppressed guinea pigs with disseminated Aspergillus fumigatus infections. Oral itraconazole administered daily at 40 mg/kg and 80 mg/kg increased survival rates in normal rabbits with disseminated disease and in immunosuppressed rats with pulmonary Aspergillus fumigatus infection, respectively.

Itraconazole has demonstrated antifungal activity in a variety of animal models infected with Candida albicans and other Candida species.

Resistance

Isolates from several fungal species with decreased susceptibility to itraconazole have been isolated in vitro and from patients receiving prolonged therapy.

Several in vitro studies have reported that some fungal clinical isolates, including Candida species, with reduced susceptibility to one azole antifungal agent may also be less susceptible to other azole derivatives. The finding of cross-resistance is dependent on a number of factors, including the species evaluated, its clinical history, the particular azole compounds compared, and the type of susceptibility test that is performed. The relevance of these in vitro susceptibility data to clinical outcome remains to be elucidated.

Candida krusei, Candida glabrata and Candida tropicalis are generally the least susceptible Candida species, with some isolates showing unequivocal resistance to itraconazole in vitro.

Itraconazole is not active against Zygomycetes (e.g., Rhizopus spp., Rhizomucor spp., Mucor spp. and Absidia spp.), Fusarium spp., Scedosporium spp. and Scopulariopsis spp.

Studies (both in vitro and in vivo) suggest that the activity of amphotericin B may be suppressed by prior azole antifungal therapy. As with other azoles, itraconazole inhibits the 14C-demethylation step in the synthesis of ergosterol, a cell wall component of fungi. Ergosterol is the active site for amphotericin B. In one study the antifungal activity of amphotericin B against Aspergillus fumigatus infections in mice was inhibited by ketoconazole therapy. The clinical significance of test results obtained in this study is unknown.

Clinical Studies

Oropharyngeal Candidiasis

Two randomized, controlled studies for the treatment of oropharyngeal candidiasis have been conducted (total n=344). In one trial, clinical response to either 7 or 14 days of itraconazole oral solution, 200 mg/day, was similar to fluconazole tablets and averaged 84% across all arms. Clinical response in this study was defined as cured or improved (only minimal signs and symptoms with no visible lesions). Approximately 5% of subjects were lost to follow-up before any evaluations could be performed. Response to 14 days therapy of itraconazole oral solution was associated with a lower relapse rate than 7 days of itraconazole therapy. In another trial, the clinical response rate (defined as cured or improved) for itraconazole oral solution was similar to clotrimazole troches and averaged approximately 71% across both arms, with approximately 3% of subjects lost to follow-up before any evaluations could be performed. Ninety-two percent of the patients in these studies were HIV seropositive.

In an uncontrolled, open-label study of selected patients clinically unresponsive to fluconazole tablets (n=74, all patients HIV seropositive), patients were treated with itraconazole oral solution 100 mg b.i.d. (Clinically unresponsive to fluconazole in this study was defined as having received a dose of fluconazole tablets at least 200 mg/day for a minimum of 14 days.) Treatment duration was 14-28 days based on response. Approximately 55% of patients had complete resolution of oral lesions. Of patients who responded and then entered a follow-up phase (n=22), all relapsed within 1 month (median 14 days) when treatment was discontinued. Although baseline endoscopies had not been performed, several patients in this study developed symptoms of esophageal candidiasis while receiving therapy with itraconazole oral solution. Itraconazole oral solution has not been directly compared to other agents in a controlled trial of similar patients.

Esophageal Candidiasis

A double-blind randomized study (n=119, 111 of whom were HIV seropositive) compared itraconazole oral solution (100 mg/day) to fluconazole tablets (100 mg/day). The dose of each was increased to 200 mg/day for patients not responding initially. Treatment continued for 2 weeks following resolution of symptoms, for a total duration of treatment of 3-8 weeks. Clinical response (a global assessment of cured or improved) was not significantly different between the two study arms, and averaged approximately 86% with 8% lost to follow-up. Six of 53 (11%) itraconazole-treated patients and 12/57 (21%) fluconazole-treated patients were escalated to the 200 mg dose in this trial. Of the subgroup of patients who responded and entered a follow-up phase (n=88), approximately 23% relapsed across both arms within 4 weeks.

Last reviewed on RxList: 4/12/2012
This monograph has been modified to include the generic and brand name in many instances.

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