A dosing nomogram for continuous infusion intravenous naloxone

Naloxone hydrochloride is extremely valuable for diagnosing and managing the opioid overdose. Due to naloxone's short half life and a long duration of action of most opioids, repeated naloxone dosing often is required to prevent the recurrence of respiratory depression. An alternative to repeated bolus administration is a continuous IV infusion. We conducted a two-phase study to determine the pharmacokinetics of naloxone and to develop a continuous dosing nomogram. In the first phase seven patients were given an IV bolus dose alone and serial plasma naloxone levels were determined. Naloxone elimination was found to be biexponential with the mean beta half life equal to 0.023 +/- 0.002 reciprocal minutes in two patients and 0.015 +/- 0.02 reciprocal minutes in five patients. In the second phase ten volunteers were given either a 2-mg or a 4-mg bolus dose followed by a 1.5-mg/hr or a 3-mg/hr continuous infusion. The mean volume of distribution of the central compartment was found to be 0.806 +/- 0.408 L/kg. The mean beta rate constant of elimination was found to be 0.036 +/- 0.027 reciprocal minutes. A computer simulation of the pharmacokinetic parameters determined in our study found that a continuous infusion of two-thirds of the bolus dose that resulted in reversal each hour will maintain the plasma naloxone levels equal to or greater than the naloxone levels that would have existed 30 minutes following the bolus dose.