NMS Pharmaceuticals Inc. Monday said it will extend by one year the expiration of 600,000 warrants that had been scheduled to expire on July 21, 1986. First sold in 1983 for 25 cents apiece, each warrant can be traded for a share of NMS common stock at a conversion price of $7.75 a share. Traded over-the-counter, NMS stock closed Monday at $5.25 a share. A company spokesman said the low price prompted the decision to extend the warrants. Based in Newport Beach, NMS develops drug delivery systems and diagnostic test kits.