Pharmacokinetics and absorption of posaconazole oral suspension under various gastric conditions in healthy volunteers

Factors influencing pharmacokinetics of prophylactic posaconazole in patients undergoing allogeneic stem cell transplantation

The objectives of the present study were to elucidate the factors influencing the pharmacokinetics of prophylactically administered posaconazole in allogeneic hematopoietic stem cell transplant (SCT) recipients. Between May 2007 and November 2008, clinical data were obtained from all SCT recipients at the University Hospital of Cologne undergoing therapeutic drug monitoring (TDM) of serum prophylactic posaconazole concentrations. The posaconazole concentrations were determined by high-performance liquid chromatography. We developed a population pharmacokinetic model using nonlinear mixed-effect modeling (NONMEM). The list of covariates tested included age; body weight; body height; gender; posaconazole dose; race; coadministration of antineoplastic chemotherapy; day of stem cell transplantation; concomitant ranitidine, pantoprazole, cyclosporine, or tacrolimus administration; coincident fever; diarrhea; and plasma gamma-glutamyltransferase activity. A total of 149 serum posaconazole concentrations from 32 patients were obtained. A one-compartment model with first-order absorption and elimination as the basic structural model appropriately described the data, with the apparent clearance being 75.8 liters/h (95% confidence interval [CI], 65.2 to 86.4 liters/h) and the apparent volume being distribution of 835 liters (95% CI, 559 to 1,111 liters). Among the covariates tested, significant effects were found for age (decrease in the volume of distribution of 123 liters per year of age) and the presence of diarrhea (59% loss of bioavailability). A basis for prediction of the mean posaconazole concentrations in allogeneic SCT recipients with hematological malignancies is provided for a given dose. Corresponding adjustments of the starting dose according to the presence of diarrhea and according to age appear to be justified before TDM results are available.

Role of posaconazole in the treatment of oropharyngeal candidiasis

Posaconazole is the newest azole antifungal approved by the US Food and Drug Administration, and possesses a broad spectrum of activity against numerous yeasts and filamentous fungi. It is available as an oral suspension and is generally well tolerated by patients, but gastrointestinal absorption is sometimes inadequate and remains a clinical concern in treating deep-seated infections. It is used routinely and effectively for the prophylaxis of invasive fungal infections in immunosuppressed hosts and is an effective treatment of oropharyngeal candidiasis, including azole-resistant disease.

Pharmacokinetics of a single dose of the antifungal posaconazole as oral suspension in subjects with hepatic impairment

OBJECTIVE

To evaluate posaconazole pharmacokinetics in subjects with different degrees of hepatic impairment compared with matched healthy subjects.

RESEARCH DESIGN AND METHODS

A total of 37 subjects were enrolled in this open-label, single-dose, parallel-group study; 19 with hepatic impairment and 18 healthy subjects with matching demographics. Each subject received a single 400-mg oral dose of posaconazole after a high-fat meal. Blood samples for analysis were taken up to 648 h ( approximately 4 weeks) postdose.

RESULTS

Compared with maximum plasma concentration (C(max)) values in matched subjects with normal hepatic function, values were higher among subjects with moderate hepatic impairment (517 vs. 724 ng/mL) but lower among subjects with severe hepatic impairment (608 vs. 403 ng/mL). No clear trend toward increased or decreased exposure was observed with increasingly severe hepatic impairment, and extensive overlap occurred between normal and hepatically impaired subjects. Therefore, pharmacokinetic variables C(max) and area under the curve from time 0 to the time of final quantifiable sample (AUC(tf)) values were pooled for subjects with hepatic impairment. Pooled C(max) values were similar to the pooled normal groups (607 vs. 605 ng/mL), whereas there was an overall 36% increase in exposure (AUC(tf)) for the pooled hepatic impairment group compared with the pooled normal group. Posaconazole was well-tolerated, with six (33%) healthy subjects and six (32%) hepatically impaired subjects reporting adverse events.

CONCLUSIONS

The data from this small single-dose study suggest posaconazole is safe. Furthermore, although limited by the small number of subjects enrolled, the authors feel that dose adjustments are probably not necessary in patients with hepatic impairment; however, physicians should continue to monitor posaconazole use in patients with hepatic impairment.

The current role of amphotericin B lipid complex in managing systemic fungal infections

BACKGROUND

An increase in the number of immunocompromised patients has led to a rising burden of systemic fungal infections. Historically, conventional amphotericin B has been used to treat these infections due to its broad spectrum of activity. The development of lipid-based amphotericin B agents, such as Abelcet * (ABLC), has allowed clinicians to take advantage of the broad spectrum of activity of amphotericin B while reducing adverse events. As well as this, a number of new antifungal agents have been developed in recent years which have significantly added to the treating physician's antifungal armamentarium. * Abelcet is a registered trade name of Cephalon Ltd, Herts, UK.

OBJECTIVES

Review the clinical data that support the use of ABLC and discuss the evidence for its continuing role in the treatment of invasive fungal infections in light of the introduction of newer antifungal agents.

METHODS

Published studies were identified by searching the MEDLINE database and the Cochrane Centre for Reviews up to August 2009. The search was conducted using the following key words: Amphotericin, Lipid, Abelcet, AmBisome, Efficacy, Nephrotoxicity, Renal, Toxicity.

FINDINGS

ABLC is effective and well-tolerated in the treatment of systemic fungal infections and remains a valuable therapeutic option in a variety of immunocompromised patients due to its broad antifungal spectrum and rarity of resistance.

LIMITATIONS

Data from randomised controlled trials of lipid-based amphotericin B formulations, as well as head-to-head comparison studies between ABLC and other antifungal agents are limited. In addition, the review uses a narrative approach and relies to a great extent on the authors' personal views and experiences.

Efficacy of posaconazole in a murine disseminated infection by Candida tropicalis

We evaluated the efficacy of posaconazole against Candida tropicalis in a systemic infection model with immunosuppressed mice. Posaconazole at 50 mg/kg of body weight/day prolonged the survival of mice and reduced the fungal tissue burden of mice infected with any of the five strains tested, with the exception of one strain that had a high MIC against this drug. Our results demonstrate the efficacy of posaconazole in the treatment of invasive murine infection caused by C. tropicalis.

Invasive fungal infections in the paediatric and neonatal population: diagnostics and management issues

Invasive fungal infections in children appear to have increased over the past few decades. Especially neonates and children with primary and secondary immunodeficiencies are at risk. Candida and Aspergillus spp. are the most commonly isolated organisms. In addition, Malassezia may cause systemic infections in newborns and zygomycosis is important because of its rising incidence and high case fatality rate. Timely diagnosis and initiation of appropriate antifungal therapy is imperative for improving outcomes. However, traditional techniques are time-consuming and representative sample material, using invasive procedures, may be difficult to obtain in the paediatric setting. This review provides an overview of the advances in detection and rapid species identification, with a focus on issues relevant in these settings. Subsequently, the current antifungal treatment options for neonates and children are discussed in light of the antifungal spectrum of the available agents and the specific pharmacokinetic properties in different age groups. Although a multitude of newer antifungal compounds have become available within the last decade, further studies are necessary to clearly establish the role for each of these agents among neonates and children.

Correlation of in vitro activity, serum levels, and in vivo efficacy of posaconazole against Rhizopus microsporus in a murine disseminated infection

A broth microdilution method was used to evaluate the in vitro activities of seven antifungal agents against 15 clinical strains of Rhizopus microsporus. Amphotericin B (AMB) and posaconazole (POS) were the most active drugs. In a model of disseminated R. microsporus infection in immunosuppressed mice, we studied the efficacy of POS administered once or twice daily against four of the strains previously tested in vitro and compared it with that of liposomal AMB (LAMB). LAMB was the most effective treatment for the two strains with intermediate susceptibility to POS. For the two POS-susceptible strains, LAMB and POS at 20 mg/kg of body weight twice a day orally showed similar efficacies. The in vivo efficacy of POS administered twice a day orally correlated with the in vitro susceptibility data and the serum drug concentrations.

Therapeutic drug monitoring of posaconazole: a monocentric study with 54 adults

Posaconazole is a potent broad-spectrum triazole antifungal. Little is known about the prevalence and risk factors for low plasma posaconazole concentrations (PPCs). We retrospectively reviewed all adult patients whose PPCs were measured after at least 5 days of treatment between April 2006 and July 2008 at the Hôpital Necker Enfants Malades. A low PPC was defined as a concentration lower than 500 ng/ml. Fifty-four patients were included: 36 receiving prophylactic (200 mg three times a day) and 18 receiving curative (400 mg twice a day) posaconazole therapy. The prevalence of low PPCs was 44% (16/36) in the prophylaxis group and 22% (4/18) in the curative-treatment group. In the prophylaxis group, low PPCs tended to be more frequent in cases of digestive disease (62.5% versus 30%; P = 0.051) and were significantly more frequent among patients with diarrhea (71.4% versus 27%; P = 0.009) or mucositis (100% versus 33%; P = 0.004). In the curative-treatment group, low PPCs were significantly more frequent in cases of diarrhea (75% versus 7%; P = 0.018). In the prophylaxis group, the only two patients who subsequently developed invasive fungal infections exhibited low PPCs. The only adverse event was hepatotoxicity for 2/54 patients (3.7%), which was not related to high plasma drug concentrations. In conclusion, low PPC is common, significantly more frequent in cases of diarrhea or mucositis, and potentially associated with subsequent invasive fungal infection. Therapeutic drug monitoring of posaconazole is therefore mandatory for immunosuppressed adults, at least for those with gastrointestinal disorders.

Pharmacokinetics of posaconazole administered orally or by nasogastric tube in healthy volunteers

The use of a nasogastric tube is one means of administering antifungal therapy to critically ill patients unable to receive medication via the oral route. This was a phase 1, open-label, single-center, randomized, crossover study of posaconazole administered via nasogastric tube in healthy volunteers. Each subject received two 400-mg single doses of posaconazole, one administered orally and one administered by nasogastric tube, with a 7-day washout period between each dose. Posaconazole was administered 5 to 10 min after subjects received a nutritional supplement. Blood samples for pharmacokinetic analysis were obtained up to 120 h postdose. The analysis of variance estimate of the study population suggests that the posaconazole nasogastric tube administration least-square mean values of observed maximum concentration (C(max)), area under the plasma concentration-time curve (AUC) to the last measurable concentration, and AUC to time infinity were 81%, 76%, and 77%, respectively, of the corresponding oral administration values. The reason for lower C(max) and AUC values when posaconazole is administered via the nasogastric tube route is not known. Oral and nasogastric tube administration of a single 400-mg dose of posaconazole suspension was safe and well tolerated in healthy adult subjects. The incidence and nature of treatment-emergent adverse events were similar with both administration routes, and no serious adverse events or clinically significant laboratory test or vital sign abnormalities were reported. Obtaining plasma posaconazole concentrations may be warranted when posaconazole is given to patients via a nasogastric tube to ensure adequate posaconazole exposure. Strategies that have been shown to enhance posaconazole exposure (such as splitting the dose and minimizing the use of proton pump inhibitors) may also be used.

Recent Publications on Medications and Pharmacy

Hospital Pharmacy presents this feature to keep pharmacists abreast of new publications in the medical/pharmacy literature. Articles of interest regarding a broad scope of topics are abstracted monthly. Suggestions or comments may be addressed to Jacyntha Sterling, Drug Information Specialist at Saint Francis Hospital, 6161 S Yale Ave, Tulsa, OK 74136 or e-mail: jasterling@saintfrancis.com .