Effects of serum lipoproteins on cyclosporine A cellular uptake and renal toxicity in vitro

Supratherapeutic posaconazole concentrations associated with hyperlipidemia in a patient with HSCT

Posaconazole is a potent, extended-spectrum triazole antifungal used for the treatment and prophylaxis of serious fungal infections. Previous reports have demonstrated hyperlipidemia resulted in significant changes in posaconazole pharmacokinetics and tissue distribution in rats. However, the effect of hyperlipidemia on the pharmacokinetics of posaconazole in patients has not yet been reported. We report a case of a 34-year-old woman who experienced a supratherapeutic posaconazole trough concentration (PTC) associated with hyperlipidemia after haploidentical hematopoietic stem cell transplantation (HSCT). The patient was admitted 13 months after HSCT for recurrent cough and sputum. She was treated with caspofungin due to developing invasive fungal infection of Candida tropicalis. After 10 days, caspofungin was discontinued due to the poor therapeutic efficacy and replaced with amphotericin B. Afterwards, the condition of the patient improved significantly and she was switched to daily oral posaconazole tablet. Therapeutic drug monitoring (TDM) of posaconazole showed a PTC was 3.2 mg/L. After discharge, she continued to receive posaconazole tablet as antifungal treatment. Two months later, laboratory tests at outpatient showed her blood lipid levels were significantly elevated and PTC was increased to 9.38 mg/L. Therefore, the posaconazole tablet was discontinued and she received lipid-lowering therapy. A few days later, the PTC was down to 5.22 mg/L. No medication errors and significant drug interactions were found. Hence, supratherapeutic PTC for this patient may be caused by hyperlipidemia which altered pharmacokinetics of posaconazole. Our findings highlight the need for close TDM in order to avoid supratherapeutic PTC if hyperlipidimia occurs during posaconazole use.

Old and New Calcineurin Inhibitors in Lupus Nephritis

Calcineurin inhibitors (CNIs) are drugs that inhibit calcineurin, a key phosphatase that dephosphorylates a transcription factor called the nuclear factor of activated T cells (NFAT), allowing its translocation into the nucleus of quiescent T cells. In the nucleus, NFAT activates interleukin 2, which stimulates the proliferation and differentiation of T-cells. CNIs can also stabilize the actin cytoskeleton of podocytes reducing proteinuria. Thanks to these characteristics, CNIs have been often used in the treatment of autoimmune diseases. However, the therapeutic index of CNIs is narrow, and their interactions with other drugs can increase toxicity or reduce efficacy. In lupus nephritis, cyclosporine and tacrolimus have been used both in induction and maintenance therapies. Observational studies and randomized controlled trials showed that both cyclosporine and tacrolimus can increase efficacy. Tolerance is satisfactory if low doses are used and the patient is carefully monitored. More recently, a new CNI, called voclosporin (VCS), has been approved by the Food and Drug Administration for use in lupus nephritis. VCS offers potential advantages over other CNIs. In two large multiethnic trials, VCS was not associated with adverse renal and metabolic events and obtained positive results despite a novel and rapid corticosteroid tapering regime.

Prevention of complications from use of conventional immunosuppressants: a critical review

Synthetic immunosuppressive drugs are largely used in immune-related renal diseases and in kidney transplantation. Most of these drugs have a low therapeutic index (the ratio that compares the blood concentration at which a drug becomes toxic and the concentration at which the drug is effective), which means that the drug should be dosed carefully and the patient monitored frequently. In this review, we consider the categories of synthetic immunosuppressive agents more frequently and conventionally used in clinical nephrology: glucocorticoids, Aalkylating agents (cyclophosphamide, chlorambucil), purine synthesis inhibitors (azathioprine, mycophenolate salts) and calcineurin inhibitors (cyclosporine, tacrolimus). For each category the possible side effects will be reviewed, the general and specific measures to prevent or treat the adverse events will be suggested, and the more common mistakes that may increase the risk of toxicity will be described. However, the efficacy and safety of immunosuppressive agents depend not only on the pharmacologic characteristics of single drugs but can be influenced also by the clinical condition and genetic characteristics of the patient, by the typology and severity of the underlying disease and by the interaction with other concomitantly used drugs.

Pharmacokinetic alterations in poloxamer 407-induced hyperlipidemic rats

1. Plasma lipid profile abnormalities in hyperlipidemia can potentially alter the pharmacokinetics of a drug in a complex manner. To evaluate these pharmacokinetic alterations in hyperlipidemia and to determine the underlying mechanism(s), poloxamer 407-induced hyperlipidemic rats (HL rats), a well-established animal model of hyperlipidemia have been used. 2. In this review, we summarize findings on the pathophysiological and gene expression changes in drug-metabolizing enzymes and transporters in HL rats. We discuss pharmacokinetic changes in drugs metabolized primarily via hepatic cytochrome P450 (CYPs) in terms of alterations in hepatic intrinsic clearance (CL^'_int), free fraction in plasma (f_u) and hepatic blood flow rate (Q_H), depending on the hepatic excretion ratio, as well as drugs eliminated primarily by mechanisms other than hepatic CYPs. 3. For lipoprotein-bound drugs, increased binding to lipoproteins resulted in lower f_u values and volumes of distribution, with some exceptions. Generally, slower non-renal clearance (or total body clearance) of drugs that are substrates of hepatic CYP3A and CYP2C is well explained by the following factors: alterations in CL^'_int (due to down-regulation of hepatic CYPs), decreased f_u and/or possible decreased Q_H. 4. These consistent findings across studies in HL rats suggest more studies are needed at the clinical level for optimal pharmacotherapies for hyperlipidemia.

Hyperlipidemia Alters the Pharmacokinetics of Posaconazole and Vincristine Upon Co-Administration in Rats

Objectives

Co-administration of posaconazole (PSZ) and vincristine (VCR) in the treatment of patients with acute lymphoblastic leukemia increases the neurotoxicity of VCR. Our aim is to study the effect of increased lipoprotein levels on the pharmacokinetics of PSZ and VCR upon co-administration in rats.

Methods

Rats were assigned to three groups, normolipidemic (NL), intermediate hyperlipidemic (IHL), and extreme hyperlipidemic (HL) groups. All rats were administered PSZ orally followed by VCR intravenously 4 h later. For the pharmacokinetic study, serial plasma samples were collected over 96 h and for tissue distribution study; plasma, lung, and liver tissues were collected over 48 h post oral dosing.

Results

Posaconazole showed higher plasma concentrations than VCR at all time points. Co-administration of VCR with PSZ reduced PSZ weight normalized oral clearance, increased PSZ area under the plasma concentration–time curve (AUC) from time zero to infinity, showed higher PSZ liver concentrations, and increased VCR volume of distribution of the central compartment. Upon increasing the lipoprotein levels, PSZ showed higher plasma availability and delayed tissue distribution, whereas VCR had shown a significant decrease in PSZ AUC_0-24h, AUC_0-tlast, and AUC_o-inf (NL = IHL > HL) and a significant increase in the volume of distribution (NL = IHL < HL). Vincristine has shown higher tissue uptake and concentrations.

Conclusion

Monitoring cholesterol and triglyceride levels in patients with acute lymphoblastic leukemia is advisable to decrease VCR neurological side effect incidences and delay the activity of both PSZ and VCR.

Pharmacokinetics of metformin in the rat: assessment of the effect of hyperlipidemia and evidence for its metabolism to guanylurea

Metformin pharmacokinetics are highly dependent upon organic cationic transporters. There is evidence of a change in its renal clearance in hyperlipidemic obese patients, and no information on its metabolic fate. To study some of these aspects, the influence of poloxamer 407 (P407)-induced hyperlipidemia on metformin pharmacokinetics was assessed. Control and P407-treated adult male rats were administered 30 mg/kg metformin intravenously (i.v.). The pharmacokinetic assessments were performed at 2 time points, 36 and 108 h, following the intraperitoneal dose of P407 (1 g/kg). mRNA and protein expressions of cationic drug transporters were also measured. There was no evidence of a change in metformin pharmacokinetics after i.v. doses as a consequence of short-term hyperlipidemia, and a change in transporter mRNA but not protein expression was observed in the P407- treated rats 108 h after P407 injection. Urinary recovery of unchanged drug was high (>90%) but incomplete. Presumed metabolite peaks were detected in chromatograms of hepatocytes and microsomal protein spiked with metformin. Comparative chromatographic elution times and mass spectra suggested that one of the predominant metabolites was guanylurea. Hyperlipidemia by itself did not affect the pharmacokinetics of metformin. Guanylurea is a putative metabolite of metformin in rats.