Effect of acute hepatic failure on the hepatic first-pass effect of 5-fluorouracil in rats

Fabrication and Use of Poly(d,l-lactide-co-glycolide)-Based Formulations Designed for Modified Release of 5-Fluorouracil

5-fluorouracil (5-FU) is a chemotherapeutic agent that has been used for the treatment of a variety of malignancies since its initial introduction to the clinic in 1957. Owing to its short biological half-life, multiple dosings are generally required to maintain effective 5-FU plasma concentrations throughout the therapeutic period. Clinical studies have shown that continuous 5-FU administration is generally superior to bolus injection as exhibited by lower toxicities and increased therapeutic efficacy. Optimal therapeutic efficacy, however, is often compromised by the limiting therapeutic index. Whilst oral formulations are also used, these suffer from the drawbacks of variable bioavailability and first-pass metabolism. As a result, sustained release formulations of 5-FU have been investigated in an effort to mimic the kinetics of continuous infusion particularly for situations where local delivery is considered appropriate. The biocompatible, biodegradable, and highly tunable synthetic polymer, poly(d,l-lactide-co-glycolide) (PLGA), is widely used as a vector for sustained drug delivery, however, issues such as insufficient loading and inappropriate burst release kinetics have dogged progress into the clinic for small hydrophilic drugs such as 5-FU. This review provides introductory information about the mechanism of action, pharmacokinetic and physicochemical properties, and clinical use of 5-FU that have contributed to the development of PLGA-based 5-FU release platforms. In addition, this review provides information on fabrication methods used for a range of 5-FU-loaded PLGA formulations and discusses factors affecting the release kinetics of 5-FU as well as the in vitro and in vivo antitumor or antiproliferative efficacy of these platforms.

Liver-to-plasma vaniprevir (MK-7009) concentration ratios in HCV-infected patients

BACKGROUND

Some drugs that are actively taken up into the liver exhibit greater than dose proportional increases in plasma exposure, although human liver-to-plasma concentration ratios have rarely been evaluated. Understanding these relationships has implications for drug concentrations at the target site for certain classes of compounds, such as direct-acting antivirals, targeted towards HCV.

METHODS

Treatment-experienced, chronic HCV non-cirrhotic patients (n=3) received vaniprevir (600 mg or 300 mg twice daily) on days 1-3 and (600 mg or 300 mg single dose) on day 4. Core needle biopsy was performed at 6 or 12 h post-dose on day 4. Blood samples were collected pre-dose on days 1 and 4, and for 24 h post-dose on day 4. The primary study objective was the hepatic concentration of vaniprevir at 6 and 12 h post-dose.

RESULTS

Vaniprevir plasma pharmacokinetic parameters increased in a greater than dose-proportional manner between the 300 mg and 600 mg doses, with approximately fivefold increases in AUC0-12 and Cmax associated with a twofold increase in dose (AUC0-12, 10.6 μM/h to 59.5 μM/h; Cmax, 2.60 μM to 13.5 μM). In the 300 mg and 600 mg dose groups, mean liver concentrations of vaniprevir were 84.6 μM and 169 μM at 6 h post-dose, and 29.4 μM and 53.7 μM at 12 h post-dose. Liver concentrations were higher than plasma with liver-to-plasma concentration ratios of approximately 20-280.

CONCLUSIONS

These data confirm higher vaniprevir concentrations in human liver compared with plasma and demonstrate that measurement of human liver drug concentration using needle biopsy is feasible.

Effect of cimetidine on pentamidine induced hyperglycemia in rats

The antiprotozoal agent pentamidine, used for the treatment of Pneumocystis jirovecii pneumonia (PCP), is known to cause abnormalities in blood glucose homeostasis, such as hypoglycemia and hyperglycemia. Pentamidine has been reported to be a substrate of organic cation transporter 1 (OCT1). We investigated the combination effects of cimetidine, an OCT1 inhibitor, on the pharmacokinetics of pentamidine and on pentamidine-induced hyperglycemia. Pentamidine was infused intravenously to rats for 20 min at a dose of 7.5 or 15 mg/kg and serum samples were obtained periodically. The serum concentration of glucose did not change significantly after pentamidine infusion at 7.5mg/kg, while it increased with pentamidine at 15 mg/kg, and the maximal concentration of glucose was 167 ± 36 mg/dl, 30 min after the start of pentamidine infusion. Cimetidine (50mg/kg) enhanced the pentamidine-induced elevation of glucose concentration and the maximal concentration of glucose was 208 ± 33 mg/dl in the pentamidine 15 mg/kg treated group. Cimetidine combination significantly reduced total body clearance of pentamidine and increased pentamidine concentrations in the liver, kidneys, and lungs. A significant correlation was found between changes in serum glucose concentrations and serum concentrations of pentamidine 30 min after the start of pentamidine infusion. These results suggest that the hyperglycemic effect of pentamidine is dependent on the concentration of pentamidine and can be enhanced by cimetidine combination.

Entrapment of 5-fluorouracil into PLGA matrices using supercritical antisolvent processes

Objectives

Two different supercritical antisolvent processes were performed to co-precipitate 5-fluorouracil (5-FU) and poly(lactide-co-glycolide) simultaneously. 5-FU is a hydrophilic antitumor agent, and is more effective when administered at a lower dose for a longer period of time.

Methods

Controlled-release polymeric systems of 5-FU were produced, and morphology, thermal behavior, in-vitro release and cytotoxicity of microparticles were analysed.

Key findings

Dissolution studies showed that 33% of drug was released in 21 days, which represents a long-lasting profile. To evaluate the efficacy of the released drug on cancer cells, the MTT assay cytotoxicity test was performed using human lung carcinoma A549 cell lines. There was no significant difference between the cell inhibition rates of the released drug and unprocessed 5-FU at the same drug concentration level. IC50 values were 69.12 mg/ml for unprocessed 5-FU and 68.71 mg/ml for the released drug.

Conclusions

Application of supercritical processing for co-precipitation of 5-FU and PLGA provided mild and non-aqueous conditions, so the hydrophilic drug incorporated in the polymer had good stability during the process.