Effects of Indometacin, Naproxen and Paracetamol on Regional Blood Flow in Rabbits: A Microsphere Study

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Abstract
Ulcerogenic side-effects and prostaglandin [PG] synthesis-inhibiting capacity are well documented in indomethacin treatment. Indomethacin reduces gastrointestinal blood flow. Naproxen and paracetamol, PG synthesis-inhibitors, have few ulcerogenic side effects. To study the indomethacin effects and whether naproxen and paracetamol have similar effects, the labeled microsphere technique was used. The regional blood flow determinations were made before and 12-15 min after the injection of the drugs. Indomethacin, 3 mg/kg, reduced gastrointestinal blood flow and increased arterial blood flow to the liver. Naproxen, 10 mg/kg, and paracetamol, 25 mg/kg, had no effects except for a very small decrease in liver blood flow with paracetamol. Under light general anesthesia, PG evidently influences resting blood flow in the gastrointestinal tract, liver and parts of the brain. The results raise doubts whether naproxen and paracetamol inhibit PG synthesis in and these tissues and offer a plausible explanation as to why naproxen paracetamol are usually well tolerated in the gastrointestinal tract. None of the drugs tested influenced resting blood flow in muscles, tendons, bones, joints or synovial membranes.