[Clinical-pharmacological and pharmacokinetic studies with naproxen]

d-2-(6'-Methoxy-2'-naphthyl)-propionic acid (naproxen) is bound in blood to a high degree to plasma protein. After oral application naproxen is absorbed rapidly and completely. The mean biological half-life in man is fourteen hours. This gives us the possibility of controlling the symptoms of disease with two daily doses. In man, 99% of naproxen is excreted in the urine, either unchanged or glucuronized and as its 6-des-methyl metabolite. There is a linear increase of plasma levels with daily doses of up to 500 mg. Higher naproxen doses do not produce higher blood levels but lead to a faster excretion. This probably depends in part on a saturation of the binding sites in plasma. Differences in affinity of some compounds for binding sites in plasma are responsible for a potential interaction between naproxen and other agents, such as warfarin, acetyl salicylic acid (ASA) and sulfonylureas. These interactions are discussed. In a double-blind trial the influence of naproxen and ASA on the gastric mucosa of healthy volunteers has been compared. The results of gastroscopic findings as well as laboratory tests are reported.