Patients with chronic hepatitis C virus (HCV) infection are often asymptomatic with few clinical signs of liver disease. Recognition of the presence of fibrosis or cirrhosis is difficult without liver biopsy, but with the availability of effective treatments, such as interferon, and the potential for progression to hepatoma in some cases, an accurate measure of the stage of disease is important. Serum hyaluronic acid (HA) has been identified as a potential marker of fibrosis or cirrhosis in other settings. In a prospective study in 130 chronic HCV carriers therefore, serum HA concentrations were compared with conventional liver function tests (including alanine aminotransferase (ALT), a-glutathione-S transferase (GST) and serum HCV RNA in order to determine which identified the stage of liver fibrosis as assessed by liver biopsy most accurately. The median HA concentrations according to the stage of fibrosis 0, 1 & 2, 3 and 4 & 5 were 17 g l-1 (range 5-37), 17 g l-1 (5-80), 30 g l-1 (10-105) and 350 g l-1 (20-800) respectively. The median HA concentration in stage 4 & 5 was significantly greater than in stages 0, 1 & 2 or 3. Serum HA concentration rose with age, but even when adjusted for age the median HA at stage 4 & 5 was greater than all other groups (95% CI of difference between the medians exceeded 0). Thus, serum HA gave a sensitivity and specificity for stage 4 & 5 fibrosis of 85% and 88% respectively, exceeding those for ALT or GST. In contrast, serum ALT or GST levels were not correlated with the stage of fibrosis although ALT was significantly greater in the cirrhotic group when compared to the group with no fibrosis (stage 0). There was no correlation between serum HA and either the grade of inflammatory changes or serum HCV RNA. These results suggest that serum hyaluronic acid is a useful marker of liver fibrosis in patients with chronic HCV infection. It could therefore be used to monitor patients at risk of progressive fibrosis, in controlled clinical trials, as a measure of response to antifibrotic therapy and in those in whom liver biopsy is difficult or contraindicated.

Cyclosporin is an immunosuppressive agent with a narrow therapeutic index. The total concentration of cyclosporin in blood is usually monitored to guide dosage adjustment and to compensate for substantial interindividual and intraindividual variability in cyclosporin pharmacokinetics. Cyclosporin is a highly lipophilic molecule and widely distributes into blood, plasma and tissue components. It mainly accumulates in fat-rich organs, including adipose tissue and liver. In blood, it binds to erythrocytes in a saturable fashion that is dependent on haematocrit, temperature and the concentration of plasma proteins. In plasma, it binds primarily to lipoproteins, including high-density, low-density and very-low-density lipoprotein, and, to a lesser extent, albumin. The unbound fraction of cyclosporin in plasma (CsA(fu)) expressed as a percentage is approximately 2%. It has been shown that both the pharmacokinetic and pharmacodynamic properties of cyclosporin are related to its binding characteristics in plasma. Furthermore, there is some evidence to indicate that the unbound concentration of cyclosporin (CsA(U)) has a closer association with both kidney and heart allograft rejection than the total (bound + unbound) concentration. However, the measurement of CsA(fu) is inherently complex and cannot easily be performed in a clinical setting. Mathematical models that calculate CsA(fu), and hence CsA(U), from the concentration of plasma lipoproteins may be a more practical option, and should provide a more accurate correlate of effectiveness and toxicity of this drug in transplant recipients than do conventional monitoring procedures. In conclusion, the distribution characteristics of cyclosporin in blood, plasma and various tissues are clinically important. Further investigations are needed to verify whether determination of CsA(U) improves the clinical management of transplant recipients.

No abstract

No abstract

1 Less than 5% of a dose of the conventional oral formulation of cyclosporin, Sandimmun®, is absorbed in liver transplant recipients with external biliary drainage, necessitating intravenous administration of the drug and exposing the patient to increased risk of severe side-effects. 2 We compared the pharmacokinetics of the conventional oral formulation of cyclosporin with that of the new microemulsion formulation, Neoral®, in eight liver transplant recipients with external biliary diversion. Patients were maintained on a continuous infusion of cyclosporin until steady-state conditions had been achieved. They were then given a test dose (10 mg kg-') of either the conventional or microemulsion formulation (randomised order) followed by the same dose of the other formulation. Parent cyclosporin concentrations were measured in whole blood samples collected at timed intervals over the 24 h after the oral doses and pharmacokinetic parameters calculated. 3 The bioavailability of cyclosporin from the microemulsion formulation was, on average, 6.5-fold (95% C.I. 1.9 to 11.1-fold) greater than that of the conventional formulation, indicating the improved absorption characteristics of the new oral microemulsion formulation during external bile drainage. 4 A significant negative correlation was found between the external bile drainage volume and bioavailability of cyclosporin from the microemulsion formulation (r = -0.8; P = 0.016), suggesting that variability in cyclosporin absorption from the microemulsion formulation may still be at least partly attributable to biledependence. Paradoxically, no relationship was found between bile volume and the very low cyclosporin bioavailability from the conventional formulation, perhaps because the volume of bile reaching the gut was below a threshold required for any consistent degree of cyclosporin absorption from this formulation to occur.5 In conclusion, the use of the new oral microemulsion formulation of cyclosporin should help to minimise the problems of cyclosporin malabsorption in most patients with external biliary drainage following liver transplantation. This will reduce requirements for the initial use of the i.v. formulation with its attendant side-effects and so may also reduce hospital stay.