Microdialysis as a sampling tool for the chemotherapeutic agent Doxorubicin

Effect of repeated bolus and continuous doxorubicin administration on bone and soft tissue concentrations- a randomized study evaluated in a tumour-free porcine model

PURPOSE

The aim of this study was to evaluate plasma and bone- and soft-tissue concentrations of doxorubicin following two administrations of either bolus or continuous infusion administered at a three-week interval. The achievement of adequate concentration at target sites is believed to be positively correlated to effect, and it has been suggested that concentrations are affected by the number of administrations.

METHODS

Eighteen female pigs were included in the study and randomized into two groups of nine receiving either a bolus or continuous infusion. The animals received a dosage of 2 mg/kg on day 1 and on day 22. From day 1 to 10, doxorubicin concentrations, as well as kidney and liver function, were monitored with plasma samples (total concentrations). On day 22, doxorubicin was measured in plasma samples (total concentration) and microdialysates (unbound concentrations) from subcutaneous tissue, muscle, synovial fluid of the knee joint, cancellous bone, and intravenously.

RESULTS

On day 22, the pharmacokinetic profiles were comparable between the two groups except for plasma AUC0 - 12 h, which was higher after continuous infusion, and intravenous Cmax, which was higher after bolus infusion. Bone- and soft tissue concentrations were below 0.10 µg/mL. Except for mean plasma (total) concentration at the 6 h timepoint on day 1 and 22 in the continuous group, which was higher after the first administration (p = 0.037), no differences in plasma concentrations were found between the two administrations.

CONCLUSION

Low mean tissue doxorubicin concentrations and similar pharmacokinetic profiles were found between the bolus and continuous infusion groups. Thus, similar anti-neoplastic efficacy is to be expected with both administration types.

Doxorubicin concentrations in bone tumour-relevant tissues after bolus and continuous infusion: a randomized porcine microdialysis study

PURPOSE

Doxorubicin is a widely used chemotherapeutic drug that can be administered intravenously as both a bolus infusion and a continuous infusion. The latter is believed to lower the risk of cardiotoxicity, which is a critical long-term complication of doxorubicin treatment. The local tissue concentrations of doxorubicin will be reflected in both treatment efficacy and toxicity, but very limited information is available. The aim of this study was to measure the concentration of doxorubicin after continuous and bolus infusion in tissue compartments around a typical location of a bone tumour.

METHODS

Sixteen pigs (female, Danish Landrace, mean weight 77 kg) were randomized into two groups of eight. Both groups received an intravenous infusion of 150 mg doxorubicin; Group 1 received a bolus infusion (10-15 min) and Group 2 received a continuous infusion (6 h). Before infusion, microdialysis catheters were placed intravenously and in four bone tumour-relevant tissue compartments (cancellous bone, subcutaneous tissue, synovial fluid of the knee joint and muscle tissue). Sampling was done (n = 15) over 24 h, and venous blood samples were collected as a reference.

RESULTS

Area under the concentration-time curve (AUC0-24 h) for plasma (total concentration) was significantly different between the two groups, while peak drug concentration (Cmax) was significantly higher in two compartments (plasma and synovial fluid of the knee joint) in Group 1 compared to Group 2. Overall, the unbound tissue concentrations were extremely low with values below 0.20 µg/mL.

CONCLUSION

The pharmacokinetic profile for doxorubicin in the investigated tissues is very similar when comparing bolus and 6 h continuous infusion.