Effect of Hydroxyzine and Meperidine on Arterial Blood Gases in Healthy Human Volunteers

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Abstract
Because hydroxyzine hydrochloride is frequently used to tranquilize patients, who are receiving narcotic analgesics for pain relief, its effect alone and in combination with meperidine on arterial blood gases and ventilation in patients at rest was evaluated in 65 healthy volunteers, who gave informed consent. Hydroxyzine hydrochloride, 1.5 mg/kg IV given over 30 seconds, caused no decrease but rather a significant (P < .001) increase in Pao2 and no increase in Paco2 and/or pH at 5, 10, 20, 30, and 60 minutes (N = 29; mean age = 47.0 years). Meperidine, 1.5 mg/kg IV given over 30 seconds, caused a significant (P < .01) reduction in Pao2 at 5 minutes indicating ventilatory depression but no increase in Paco2 and/or pH (N = 19; mean age = 32.4 years). The combination of the same doses of hydroxyzine with meperidine IV caused a significantly greater decrease in Pao2 only at 10 minutes but a greater increase in Paco2 and pH at all times for 60 minutes than did meperidine alone (N = 17; mean age = 39.5 years), which indicates greater ventilatory depression with the combination than with hydroxyzine alone. However, Pao2, Paco2 and pH remained within the awake normal ranges for Pao2, Paco2, and pH for the age group of volunteers even at 10 minutes after IV injection of the drug combination when most of the volunteers were asleep. In conclusion, hydroxyzine even when given IV in excess of the maximum IM therapeutic doses caused no changes in Pao2, Paco2 or pH, which would indicate clinically important ventilatory depression. Furthermore, blood gases remained in the normal awake range even after the combined IV administration of hydroxyzine and meperidine in excess of the maximum IM therapeutic doses.