放射線照射後に全身投与された薬物口腔組織内濃度ならびに舌乳頭血管系の変化について

抄録

Osteoradionecrosis is a serious complication occurring after radiotherapy for cancer of the oral cavity. It is often observed after surgical intervention in the irradiation filed. For preventing osteoradionecrosis, it thus seems adequate to administer antimicrobic agents before and after tooth extraction. No reports on the concentration of antimicrobic agents in these oral tissues with modified circulation system by irradiation has been yet available. In the present study, 1000 R of 3000 R radiation was given to the right mandible of rabbits and the concentration of DOXY was measured in the right mandibular gland, mandible, tongue margin, mandibular gingiva and plasma 3 days, 1 and 2 weeks, and 1, 3 and 6 months after irradiation. Each sample was taken 2 hours after 10mg/kg DOXY i. v. injection. For observing fi ne vessels in 3000 R irradiated group, on the other hand, acrylic resin was infused through the right and left common carotid artery and the right tongue margin was observed by electron scanning microscope.
Experimental results:
1) The drug concentration becomes high after 1 and 2 weeks of irradiation followed by decrease to normal level after 1 month. However, it shows an increasing trend again after 3 months. On the other hand, the ratio of tissue drug level to plasma one is normal or slightly low at 3 and 6 months after radiation.
2) The tongue papilla capillaries becomes narrow showing a constricted part 1 week after irradiation. No capillary network is however observed after 1 month and only protrusion of short capillaries from the venule is observed.
From these results, the drug concentration in irradiated oral tissues seems to somewhat decrease when an antimicrobic agent is administered after ratiotherapy. If the amount of drug is increased and a good pharmacokinetic antimicrobic agent is administered, however, the drug concentration in irradiated oral tissues seems sufficient to prevent clinical infections.