NASAL CLEARANCE IN RHESUS-MONKEYS

Gamma camera scintigraphy studies were carried out to determine a) anesthetic effects, b) the effect of varying deposition site on nasal clearance and reproducibility. a) Anesthesia effects. Six rhesus monkeys (5-7.5 kg) were studied while anesthetized with 1 ml of ketamine (100 mg/ml) only or with ketamine pretreatment followed by sodium pentobarbital (30 mg/kg). Technetium-99m labeled sulfur colloid solution was deposited in the nose and clearance from the anterior nasal region and turbinate region was measured for 30 minutes using gamma camera scintigraphy. Clearance in monkeys anesthetized with ketamine only was approximately 2-fold faster than in monkeys anesthetized with ketamine plus sodium pentobarbital. These and other studies indicate ketamine anesthesia in monkeys is superior to other anesthetics because clearance is similar to that in conscious man. b) Deposition site effects. Using the ketamine anesthesia regimen, clearance was also measured following deposition in the anterior nasal region and the turbinate region. Repeat studies were carried out for each region in each monkey, showing a high degree of reproducibility. Rapid clearance from the turbinate region resulted in only 27 +/- 4% retention at the end of 30 min; there was little clearance from the anterior region with 87 +/- 7% retention at the end of 30 min. Accurate placement of test markers is important in making reproducible measurements. In animal studies of nasally administered materials, the use of sodium pentobarbital anesthesia is likely to increase both absorption and toxicity because of prolonged contact time on the nasal epithelium.