Acute muscular dystonias Bizarre muscle spasms, mostly involving lingua-facial muscles -grimacing, tongue thrusting, toicollis, locked jaw; occurs within a few hours of a single dose or at the most in the first week of therapy. It is more common in children below 10 years and in girls, paicularly after parenteral administration; overall incidence is 2%. It lasts for one to few hours and then resolves spontaneously. One of the central anticholinergics, promethazine or hydroxyzine injected i.m. clears the reaction within 10-15 min. REF KD TRIPATHHI 8TH ED.