Potent anticonvulsant activity has been demonstrated for a large number of 1-(naphthylalkyl)-1H-imidazoles containing a variety of functional groups in the alkylene bridge. The presence of a small oxygen function in the bridge, in general, confers a high therapeutic index between anticonvulsant and depressant activity. Clinical expectations are discussed for 1-(2-naphthoylmethyl)imidazole hydrochloride (5), which is undergoing development for testing in humans.

RS-37619 showed highly potent analgesic activity when given p.o. in tests utilizing underlying inflammation. It inhibited phenylquinone-induced writhing in the mouse and rat (350 and 180 x aspirin respectively) and the pain induced by flexing the adjuvant-inflamed rat paw (approximately 800 x aspirin). The agent increased the pain threshold of compressed yeast-inflamed rat paws (3-10 x naproxen). RS-37619 did not increase the pain threshold of the non-inflamed paw and was inactive in the mouse hot plate test; therefore it is probably not a centrally acting or morphine-like agent. RS-37619 was also highly active p.o. in rat models of acute and chronic inflammation. It inhibited carrageenan-induced paw edema (36 x phenylbutazone), cotton pellet-induced granuloma (less than or equal to 1 x indomethacin) and in an 18-day test, prevented the development of adjuvant-induced arthritis (approximately 2 x naproxen). RS-37619 exhibited antiphlogistic activity in adrenalectomized rats. It did not have corticosteroid activity. When given p.o., RS-37619 lowered yeast-induced pyrexia (20 x aspirin). Gastrointestinal irritation was seen in the rat with doses greater than or equal to 6.4 mg/kg/day p.o. The agent elicited mild CNS and cardiovascular activity only at doses far in excess of those required for analgesic and anti-inflammatory activity.

A series of 4(6)- and 5-phenyl-substituted 2-amino- and 2-[(alkoxycarbonyl)amino]-1,4,5,6-tetrahydropyrimidines were prepared and evaluated for central nervous system (CNS) effects in animal models. Several 5-phenyl-substituted compounds possessed potent antidepressant activity and all compounds in this series were devoid of significant activity in any of the other CNS (anticonvulsant, muscle relaxant, and depressant) assays. The most active compound in the in vivo screen for antidepressant activity (reversal of reserpine-induced hypothermia), 2-[(methoxycarbonyl)amino]-5-phenyl-1,4,5,6-tetrahydropyrimidine was considerably more potent than tricyclic antidepressant (TCA) standards. The 2-amino parent compound on the other hand was greater than 100-fold as effective as TCA's in in vitro inhibition of norepinephrine and dopamine uptake.

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