Abstract
A vascularly isolated rabbit forelimb model simulating conditions of composite tissue allografting was used to determine the regional pharmacokinetic advantage achievable in extremity tissue components during i.a. cyclosporin A (CSA) administration. CSA was infused continuously via osmotic minipump into the right brachial artery of New Zealand rabbits at multiple doses ranging from 1.0 to 8.0 mg/kg/day. On day 6, CSA concentrations were measured in aortic whole blood, as well as in skin, muscle, bone, and bone marrow samples from both right and left forelimbs. The variation of right-sided mean CSA concentrations with dose was tissue dependent and saturable in the case of skin and bone, whereas left-sided tissue concentrations correlated significantly with systemic blood levels. At 1.0 mg/kg/day, there were no significant differences between right and left mean CSA concentrations for all four tissues examined. However, with a doubling of the i.a. dose, huge increases in local tissue CSA concentrations were produced with only very modest increases in systemic whole-blood and tissue drug levels, resulting in a 4-fold regional advantage (right/left ratio of CSA concentrations) in bone and bone marrow, 7-fold in muscle, and 14-fold in skin. With further dose increases to 8.0 mg/kg/day, the regional advantage decreased to 4-fold in skin, increased to 9-fold in bone marrow, remained relatively constant in bone, and initially decreased and then increased to 9-fold in muscle. These favorable pharmacokinetic results suggest that reduced, local doses of CSA might be useful in preventing extremity composite tissue allograft rejection with decreased systemic drug exposure.
Footnotes
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Send reprint requests to: John H. Barker, M.D., Ph.D., Division of Plastic and Reconstructive Surgery, University of Louisville School of Medicine, 320 MDR Building, 511 South Floyd St., Louisville, KY. E-mail: jhbark01{at}ulkyvm.louisville.edu
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↵1 This work was supported in part by the Jewish Hospital Foundation of Louisville, Kentucky.
- Abbreviations:
- Csystemic(i.a.)
- systemic drug concentration at steady state during i.a. infusion
- Ctarget(i.a.)
- steady-state drug concentration in target organ during i.a. infusion
- Ctarget(i.v.)
- steady-state drug concentration in target organ during i.v. infusion
- Cls
- systemic clearance
- CSA
- cyclosporin A
- CTA
- composite tissue allograft
- inf
- constant drug infusion rate
- Kp
- equilibrium distribution ratio
- Rtarget
- regional advantage
- QT
- target organ blood flow
- Received July 8, 1998.
- Accepted October 18, 1998.
- The American Society for Pharmacology and Experimental Therapeutics
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