The word cycloserine is playable in Words With Friends™, no blanks required. Because it is longer than 7 letters, you would have to play off an existing word or do it in several moves.
Words With Friends™ Letter Score: 21
Highest Scoring Words With Friends™ Play In The Letters cycloserine
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Seven Letter Word Alert: (39 words)
circles, clerics, clerisy, cloners, cloyers, coerces, coiners, concise, cornice, cornily, creoles, cronies, cryonic, cyclene, cyclers, cyclins, cyclise, cyclone, eccrine, enclose, encores, licence, license, necrose, recline, reclone, reclose, recoils, recoins, recycle, relines, reslice, scenery, science, screeny, secrecy, silence, sincere, yeelins