Continuous intravenous infusion steady-state plasma concentration

After intravenous administration of 175 mg/70 kg to five individuals, the average peak serum concentration was 1.0 mg/L achieved at 12 min.2 The concentration declined by 50% within 30 min. The plasma half-life is reported to be 3 to 4 h with a volume of distribution of 3 to 5 L/kg.1 Continuous infusion of 41 pg/kg/min after a 2-mg/kg bolus produced an average (n = 31) steady-state plasma concentration of 2.2 mg/L.3... 

During continuous intravenous infusion at an average rate of 41 ig/kg/ minute to 31 subjects, a mean steady-state plasma concentration of 2.2 pg/ ml was reported norketamine and dehydronorketamine attained mean peak plasma concentrations of 1.1 pg/ml and 0.7 pg/ml, respectively, in about 3 hours the subjects awoke at an average plasma concentration of 0.64 pg/ml (J. Idvall et al., Br. J. Anaesth., 1979, 51,1167-1173). Following an intramuscular injection of 0.5 mg/kg to 6 subjects, peak plasma concentrations of 0.10 to 0.43 pg/ml (mean 0.24) were attained in about 0.3 hour norketamine attained a mean peak plasma concentration of 0.09 pg/ml at about 1 hour (J. A. Clements et al., J. pharm. Sci., 1982, 71, 539-542). 

A mean steady-state plasma concentration of 12.7)j.g/ml was reported during the continuous intravenous infusion of l.Omg/kg/min to 6 subjects following continuous intravenous infusion of 1.5 mg/kg/min to a further 6 subjects, a mean steady-state plasma concentration of 42.7 pg/ ml was reported (A. B. Seifen et al., Anesth. Analg. curr. Res., 1979, 58, 382-386). 

Half-life less than 3 h. Dosing at intervals equal to the t/ would be so frequent as to be unacceptable, and the answer is to use continuous intravenous infusion if the tj is very short, e.g. dopamine t), 2 min steady-state plasma concentration will be reached in... 

When a drug is administered by continuous intravenous infusion, the infusion rate (Ro) required to provide a desired steady-state plasma concentration is... 

This continuous infusion method can also be employed without urine collection, and plasma clearance is then calculated as CL = infusion rate/Css. Requirements of this method include steady-state plasma concentrations and accmate measmement of infusate concentrations. Plasma clearance can also be determined following a singledose intravenous injection with multiple samples of blood taken to estimate the area under the curve (AUCo oo)- Here clearance is calculated as CL = dose/AUC. These plasma clearance methods commonly yield clearance values 10% to 15% higher than urine collection methods. ... 

After a bolus intravenous injection of 2 mg/kg followed by continuous intravenous infusion to provide a maintenance dose of 2 mg/kg to 1 neonate, plasma concentrations attained a steady-state of 7 to 8 pg/ml and declined with a half-life of 5 hours at the end of the infusion (V. Rovei et al., J. Chromat., 1982,231 Biomed. Appl., 20, 210-215). 

Intravenous ribavirin decreases mortality in patients with Lassa fever and other viral hemorrhagic fevers if started early. High concentrations inhibit West Nile virus in vitro, but clinical data are lacking. Clinical benefit has been reported in cases of severe measles pneumonitis and certain encephalitides, and continuous infusion of ribavirin has decreased virus shedding in several patients with severe lower respiratory tract influenza or parainfluenza infections. At steady state, cerebrospinal fluid levels are about 70% of those in plasma. 

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