title: Pharmacokinetics/pharmacodynamics
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  Pharmacokinetics/pharmacodynamics
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  bet | 388/654 | Sana | 03.01.2022 | Hajmi | 1,5 Mb. | | #14803 |
  Pharmacokinetics/pharmacodynamics: In newborns, after intravenous administration of 35 (n = 6) and 70 (n = 6) micrograms of naloxone, peak levels of 4 to 15 ng/mL and 9 to 20 ng/mL respectively were reached in 5 to 40 min and the mean plasma half-life after both doses was 3.1 ± 0.5 hours. Peak levels of 7 to 35 ng/ml were reached 0.5 to 2 hour after intramuscular administration of 200 microgram (n = 17). The fall in concentration after this
  was consistently biphasic with the levels declining rapidly between one and four hours and then slowly from four hours onwards. Plasma concentrations at 24–36 hours after IM administration were as high as they were 4 hours after IV administration of 35 microgram which may account for the prolonged duration of action when this route is used. [10] In 26 infants born to mothers who received pethidine, naloxone was not observed to have any agonist activity, but the recommended IV dose (0.01 mg/kg) had only a slight and delayed antagonist action as measured by respiratory function tests. A more rapid and improved antagonism was noted after this dose was doubled (0.02 mg/kg). The plasma elimination- phase half-life of naloxone after intravenous cord injection was about 3 hours. [11]
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