Higher tacrolimus trough levels and time in the therapeutic range are associated with the risk of acute rejection in the first month after renal transplantation

BACKGROUND

Tacrolimus trough levels (C₀) are used in most transplant centres for therapeutic drug monitoring (TDM) of tacrolimus (Tac). The target range of Tac C₀ has been remarkably changed, with a target as low as 3-7 ng/ml in the 2009 European consensus conference and a target of 4-12 ng/ml (preferably to 7-12 ng/ml) following the second consensus report in 2019. Our aim was to investigate whether reaching early Tac therapeutic targets and maintaining time in the therapeutic range (TTR) according to the new recommendations may be necessary for preventing acute rejection (AR) during the first month after transplantation.

METHODS

A retrospective study including 160 adult renal transplant patients (113 men and 47 women) with a median age of 36.3 (20-44) years was conducted between January 2018 and December 2019 at 103 Military Hospital (Vietnam). Tac trough levels were recorded in the first month, and episodes of AR were confirmed by kidney biopsy. Tac TTR was calculated as the percentage of time within the target range of 7-12 ng/ml, according to the 2019 second consensus report. Multivariate Cox analysis was performed to identify the correlation between the Tac target range and TTR with AR.

RESULTS

In the first month after RT, 14 (8.8%) patients experienced AR. There was a significant difference in the incidence of AR between the Tac level groups of < 4, 4-7 and > 7 ng/ml (p = 0.0096). In the multivariate Cox analysis, after adjusting for related factors, a mean Tac level > 7 ng/ml was associated with an 86% decreased risk of AR compared with that of 4-7 ng/ml in the first month (HR, 0.14; 95% CI, 0.03-0.66; p = 0.0131). Every 10% increase in TTR was associated with a 28% lower risk of AR (HR, 0.72; 95% CI, 0.55-0.94; p = 0.014).

CONCLUSION

Gaining and maintaining Tac C₀ according to the 2019 second consensus report might reduce the risk of AR in the first month following transplantation.

The pharmacokinetics of a single dose of artemisinin in subjects with liver cirrhosis. Bach Mai-Amsterdam Research Group on Artemisinin

Artemisinin is mainly eliminated by hepatic transformation. To investigate whether the clearance of artemisinin in patients with liver cirrhosis is different from healthy volunteers, a pharmacokinetic study was performed in male Vietnamese patients with Child B cirrhosis of the liver who received 500 mg of artemisinin orally. The results were compared to those found in a previous study in healthy subjects. The mean (+/- SD) area under the concentration time curve was 2365 (+/- 1761) h ng/ml; the mean (+/- SD) clearance, 382 (+/- 303)L/h. The elimination half life was 4 (+/- 1.3) h extimated by log-linear regression and 2.4 +/- 0.9 h estimated by non-linear regression using a one-compartment first order elimination model. The mean (+/- SD) absorption time was 1.55 (+/- 0.8) h. These results were not different from the results of healthy subjects and show that liver disease has no effect on the availability and clearance of oral artemisinin, indicating that artemisinin has an intermediate hepatic extraction ratio and that there is no significant first pass effect.

The pharmacokinetics of a single dose of artemisinin in patients with uncomplicated falciparum malaria

The pharmacokinetics of artemisinin was studied in 11 Vietnamese patients with uncomplicated falciparum malaria after a single 500 mg oral dose. Curative treatment with mefloquine (15 mg/kg) was provided 24 hr after the artemisinin dose. Artemisinin concentrations were measured by high-performance liquid chromatography with electrochemical detection. The following pharmacokinetic results were found (all mean +/- SD); calculated volume of distribution/bioavailability = 22.8 +/- 16.6 L.kg-1, mean absorption time = 1.16 +/- 0.92 hr, calculated maximum concentration = 364 +/- 250 micrograms.L-1 occurring at 2.88 +/- 1.71 hr after drug intake, and an elimination half-life of 2.72 +/- 1.76 hr. Bioavailability was low. These results do not differ from results in healthy subjects. Parasites disappeared rapidly, with a mean parasite clearance time of 36 hr. No relationship was found between pharmacokinetics and the parasite elimination rate. Tolerance to the single dose of artemisinin was good. No adverse effects were detected. In conclusion, pharmacokinetics of a single dose of artemisinin for uncomplicated falciparum malaria is not different from findings in healthy subjects. A single dose of 500 mg of artemisinin is effective in reducing parasitemia in nonsevere lalciparum malaria and is well-tolerated.

The pharmacokinetics of a single dose of artemisinin in healthy Vietnamese subjects

The pharmacokinetics of artemisinin was studied in 12 healthy male Vietnamese subjects after a single, 500-mg, oral dose. A total of 14 plasma samples per subject was obtained up to 48 hr after drug intake. Measurement of artemisinin concentration was performed by high-performance liquid chromatography with electrochemical detection. Tolerance was evaluated by recording subjective and objective findings including repeated physical examination, routine blood investigation, and electrocardiograms. Fitting of the concentration-time curve and pharmacokinetic calculations revealed the following results: a mean +/- SD volume of distribution/dose ratio of 19.4 +/- 6.9 L/kg, a mean +/- SD absorption half-life of 0.58 +/- 0.54 hr with a mean +/- SD calculated maximum concentration of 391 +/- 147 micrograms/L occurring at 1.81 +/- 0.73 hr after drug intake. Elimination was rapid, with a mean +/- SD elimination half-life of 2.59 +/- 0.55 hr. Peak concentrations were sufficient with regard to antimalarial activity although bioavailability appears to be very low. The relatively small interindividual variation in pharmacokinetics does not seem to be of clinical significance. Tolerance to the single dose of artemisinin was good: no adverse effects were detected. Based on these results, a treatment schedule of 2 x 500 mg of artemisinin (oral dose) per day can be advised. This will result in adequate antimalarial plasma concentrations, despite poor bioavailability, and rapid elimination.