IntroductionBecause of the high mortality of invasive fungal infections (IFIs), appropriate exposure to antifungals appears to be crucial for therapeutic efficacy and safety.Materials and methodsThis review summarises published pharmacokinetic data on systemically administered antifungals focusing on co-morbidities, target-site penetration, and combination antifungal therapy.Conclusions and discussionAmphotericin B is eliminated unchanged via urine and faeces. Flucytosine and fluconazole display low protein binding and are eliminated by the kidney. Itraconazole, voriconazole, posaconazole and isavuconazole are metabolised in the liver. Azoles are substrates and inhibitors of cytochrome P450 (CYP) isoenzymes and are therefore involved in numerous drug–drug interactions. Anidulafungin is spontaneously degraded in the plasma. Caspofungin and micafungin undergo enzymatic metabolism in the liver, which is independent of CYP. Although several drug–drug interactions occur during caspofungin and micafungin treatment, echinocandins display a lower potential for drug–drug interactions. Flucytosine and azoles penetrate into most of relevant tissues. Amphotericin B accumulates in the liver and in the spleen. Its concentrations in lung and kidney are intermediate and relatively low myocardium and brain. Tissue distribution of echinocandins is similar to that of amphotericin. Combination antifungal therapy is established for cryptococcosis but controversial in other IFIs such as invasive aspergillosis and mucormycosis.

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This meta-analysis did not support the hypothesis that lower molecular weight and substitution decrease tissue uptake of HES. Further clinical studies of HES tissue uptake are needed.

Systemic fungal infections are a major threaten for immunocompromised patients. Beside the antimycotic spectrum, the pharmacokinetic properties of an antifungal drug are crucial for its clinical efficacy. Since patients with systemic mycoses frequently present with a significant co-morbidity, pharmacokinetics under special conditions such as renal insufficiency, renal replacement therapy or impaired liver function have to be considered. Amphotericin B is eliminated unchanged by the liver and the kidney. Its plasma protein binding accounts for 95 to 99 percent. Conventional amphotericin B deoxycholate has a remarkable infusion related and renal toxicity. Therefore, lipid formulations have been developed. By now, three lipid formulations are therapeutically used: liposomal amphotericin B, amphotericin B colloidal dispersion and amphotericin B lipid complex. Striking differences in their plasma pharmacokinetics have been found. These differences can be attributed to the diverse disposition of the lipid moieties, while liberated amphotericin B displays a pharmacokinetic behavior which is independent from the lipid-formulation applied. The highest amphotericin B tissue concentrations have been found in the liver and in the spleen, followed by lung, kidney and heart. Concentrations in brain tissue are very low. Flucytosine has no relevant protein binding and is eliminated by glomerular filtration. Fluconazole, itraconazole, voriconazole, posaconazole and ravuconazole are triazoles, used for treatment of systemic fungal infections. Significant drug interactions have to be considered during therapy with triazoles, particularly in patients dependent on immunosuppression. These interactions are caused by the metabolism of triazoles in the liver where the cytochrome P450 (CYP) system is involved at a different extend as well as by their mechanisms of action. Triazoles display a favorable tissue distribution with high penetration into the central nervous system. Echinocandins such as caspofungin and micafungin are rapidly taken up by peripheral tissues, particularly by the liver. In the first 24 hours this uptake appears to be the main route of elimination from plasma. Enzymatic degradation takes place, but is independent of CYP. Thus, drug interactions are a minor problem during echinocandin treatment. The highest tissue levels of caspofungin and micafungin have been measured in the liver. Moderate concentrations are achieved in lung, spleen and kidney. Penetration into the brain is relatively poor.

Enoxaparin can be safely used for anticoagulation during CVVH resulting in higher filter lifespan compared with unfractionated heparin.

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Recent studies have shown marked increases in brain content of neuropeptide Y (NPY) after seizures induced by intraperitoneal injection of kainic acid and after pentylenetetrazole kindling in the rat. We have now investigated possible changes in the rate of biosynthesis of NPY after kainic acid treatment, by using pulse-labeling of the peptide and by determining prepro-NPY mRNA concentrations. For pulse labeling experiments, [3H]tyrosine was injected into the frontal cortex, and the incorporation of the amino acid into NPY was determined after purifying the peptide by gel filtration chromatography, antibody affinity chromatography, and reversed-phase HPLC. At 2 and 30 days after kainic acid treatment, the rate of tyrosine incorporation was enhanced by approximately 380% in the cortex. In addition, concentrations of pre-pro-NPY mRNA were determined in four different brain areas by hybridization of Northern blots with a complementary 32P-labeled RNA probe 2, 10, 30, and 60 days after kainic acid treatment. Marked increases were observed in the frontal cortex (by up to 350% of controls), in the dorsal hippocampus (by 750%), and in the amygdala/pyriform cortex (by 280%) at all intervals investigated. In the striatum only a small, transient increase was observed. The data demonstrate increased expression of prepro-NPY mRNA and an enhanced rate of in vivo synthesis of NPY as a result of seizures induced by the neurotoxin kainic acid.