When hydroxyzine is used preoperatively or prepartum, narcotic requirements may be reduced as much as 50 per cent. Thus, when 50 mg of VISTARIL (hydroxyzine hydrochloride) Intramuscular Solution is employed, meperidine dosage may be reduced from 100 mg to 50 mg. The administration of meperidine may result in severe hypotension in the postoperative patient or any individual whose ability to maintain blood pressure has been compromised by a depleted blood volume. Meperidine should be used with great caution and in reduced dosage in patients who are receiving other pre- and/or postoperative medications and in whom there is a risk of respiratory depression, hypotension, and profound sedation or coma occurring.