Pharmacokinetics of gemcitabine and 2',2'-difluorodeoxyuridine in a patient with ascites

Distribution of therapeutic monoclonal antibodies into ascites in advanced gastric cancer patients with peritoneal metastasis: case reports and literature review

BACKGROUND

Therapeutic monoclonal antibodies, including ramucirumab and nivolumab, are used to treat advanced gastric cancer (AGC). Malignant ascites is often accompanied by peritoneal metastasis in AGC patients. However, the distribution of therapeutic monoclonal antibodies into ascites has yet to be adequately investigated.

METHODS

We determined serum and ascites concentrations of ramucirumab or nivolumab and total IgG in three AGC patients with massive ascites. When serum and ascites samples were obtained on the same day, the ascites-to-serum ratio (A/S ratio) of the concentration of monoclonal antibodies was evaluated. The relationship between time after last infusion and the A/S ratio of therapeutic monoclonal antibodies was examined using 15 datasets from the present study and the literature.

RESULTS

Ramucirumab and nivolumab were detected in massive ascites at considerable amounts (A/S ratios of 0.24-0.35 for ramucirumab and 0.17-0.55 for nivolumab). A positive correlation was detected between the A/S ratios of the therapeutic monoclonal antibodies and the time after last infusion (r = 0.747). Removal of ascites using paracentesis eliminated at least 15.3%-30.3% and 5.2-27.4% of the injected ramucirumab and nivolumab, respectively. Endogenous IgG, as well as therapeutic monoclonal antibodies, were distributed into ascites; the A/S ratios for IgG were 0.22-0.45.

CONCLUSION

Our results suggest that therapeutic monoclonal antibodies, including ramucirumab and nivolumab, are distributed into massive ascites in AGC patients concomitantly with endogenous IgG. In these patients, retention of ascites and its removal may result in decreased systemic drug exposure to ramucirumab and nivolumab.

Review article: prescribing medications in patients with cirrhosis - a practical guide

BACKGROUND

Most drugs have not been well studied in cirrhosis; recommendations on safe use are based largely on experience and/or expert opinion, with dosing recommendations often based on pharmacokinetic (PK) changes.

AIM

To provide a practical approach to prescribing medications for cirrhotic patients.

METHODS

An indexed MEDLINE search was conducted using keywords cirrhosis, drug-induced liver injury, pharmacodynamics (PDs), PKs, drug disposition and adverse drug reactions. Unpublished information from the Food and Drug Administration and industry was also reviewed.

RESULTS

Most medications have not been adequately studied in cirrhosis, and specific prescribing information is often lacking. Lower doses are generally recommended based on PK changes, but data are limited in terms of correlating PD effects with the degree of liver impairment. Very few drugs have been documented to have their hepatotoxicity potential enhanced by cirrhosis; most of these involve antituberculosis or antiretroviral agents used for HIV or viral hepatitis. Paracetamol can be used safely when prescribed in relatively small doses (2-3 g or less/day) for short durations, and is recommended as first-line treatment of pain. In contrast, NSAIDs should be used cautiously (or not at all) in advanced cirrhosis. Proton pump inhibitors have been linked to an increased risk of spontaneous bacterial peritonitis (SBP) in cirrhosis and should be used with care.

CONCLUSIONS

Most drugs can be used safely in cirrhosis, including those that are potentially hepatotoxic, but lower doses or reduced dosing frequency is often recommended, due to altered PKs. Drugs that can precipitate renal failure, gastrointestinal bleeding, SBP and encephalopathy should be identified and avoided.

Intraperitoneal gemcitabine pharmacokinetics: a pilot and pharmacokinetic study in patients with advanced adenocarcinoma of the pancreas

BACKGROUND

The pyrimidine analogue gemcitabine (2', 2'-difluorodeoxycitidine, dFdC) is active against pancreatic cancer, and its high clearance (CL(tb)) and low incidence of local toxicity make it an excellent candidate for evaluation as intraperitoneal (IP) therapy. We designed a dosing schema that used multiple sequential exchanges of a peritoneal dialysate containing dFdC in an effort to produce prolonged IP dFdC exposure.

METHODS

As part of a study involving multi-modality therapy for advanced pancreatic adenocarcinoma, patients were treated with four 6-h IP dwells of dFdC (50 mg/m(2) in 2 l) over a 24-h period. A second 24-h cycle of IP dFdC therapy was repeated 1 week later. Each exchange of dialysate contained 50 mg/m(2) dFdC in 2 l of commercial 1.5% dextrose dialysis solution. Plasma and peritoneal fluid were analyzed by HPLC to determine concentrations of dFdC and its inactive metabolite 2', 2' difluorodeoxyuridine (dFdU). Clinical data were recorded to note drug toxicity and response.

RESULTS

Nine patients underwent IP dFdC therapy, and eight were able to receive two cycles. There were no recorded significant toxicities. Low plasma dFdC concentrations (<1 microg/ml) were present transiently in seven of nine patients, and dFdC was not detectable in the plasma of the other two. Plasma dFdU concentrations were low but increased gradually until 12 h and then declined little if any. IP dFdC concentrations declined rapidly, and dFdC was seldom measurable prior to administration of the next scheduled 6-h dwell. dFdU concentrations in peritoneal fluid were very low (<0.5 microg/ml) throughout treatment. The mean area under the concentration versus time curve (AUC) for dFdC in peritoneal fluid was 182 microg/ml x h, which was approximately 70x the AUC of dFdC reported in the ascites of a patient undergoing systemic dFdC therapy.

CONCLUSIONS

IP dFdC was well tolerated, and no significant toxicities were noted. The rapid decrease in peritoneal dFdC concentrations and low concentrations of IP dFdU imply almost total absorption of IP-administered dFdC. Little, if any, dFdC could be detected in plasma, but the steady-state plasma dFdU concentrations also imply absorption and inactivation of virtually all IP-administered dFdC. These findings are consistent with the known high CL(tb) and low incidence of local toxicity of dFdC and argue for its further evaluation as a drug for IP therapy.

Investigation of the pharmacokinetics of gemcitabine and 2′,2′-difluorodeoxyuridine in human plasma by liquid chromatography

Gemcitabine (2',2'-difluorodeoxycytidine, dFdC) is a difluorine-substituted deoxycytidine analogue that has demonstrated antitumor activity against solid tumors. The pharmacokinetics of dFdC and its metabolite, 2',2'-difluorodeoxyuridine (dFdU) have been studied; however, their disposition has never been evaluated in a patient with bladder cancer. A patient with bladder cancer was treated with dFdC 1000 mg/m(2) over a 30min period. The patient received a dFdC infusion once per week for 3 weeks followed by a rest week. Serial plasma samples were obtained prior to, during, and after completion of the infusion for determination of dFdC and dFdU concentrations. dFdC and dFdU concentrations were measured using normal-phase high-performance liquid chromatography and one-compartment open model methods. Maximum plasma concentrations (C(max)) and area under the plasma concentration-time curve for dFdC and dFdU were 24.5 microg/ml and 11200 microg/Lh, 49.1 microg/ml and 272,800 microg/Lh, respectively.