The pharmacokinetics of intravenous caffeine used to measure liver function were evaluated in 20 critically ill patients. Each patient received a single dose of 3.0 mg/kg of caffeine benzoate as a 30-min i.v. infusion. Caffeine serum concentrations were analysed by an enzyme-multiplied immunoassay technique (EMIT). Caffeine pharmacokinetics fitted an open one-compartment model. The mean value for the half-life (t1/2) was 9.46 +/- 4.32 h, the volume of distribution was 0.55 +/- 0.13 l/kg, and the plasma clearance (Cl) was 0.85 +/- 0.44 ml/min/kg. The pharmacokinetics parameters of caffeine in critically ill patients compared with normal volunteers were characterized by a reduction in plasma clearance and prolongation in plasma half-life, whereas the volume of distribution remained unchanged.
Mean values and standard deviations are reported for theophylline plasma clearance in 45 hospitalized geriatric patients (age greater than 65 years), distributed into two groups: Group I (n = 24) included critically ill patients admitted to the ICU on total parenteral nutrition (TPN). Group II (n = 21) included patients admitted to the Internal Medicine Ward without TPN. All patients were treated with a constant intravenous infusion of aminophylline. Group I patients had a lower mean theophylline clearance of 0.42 +/- 0.23 ml/kg/min compared to Group II 0.64 +/- 0.24 ml/kg/min (P = 0.003).
Plasma flecainide (FLC) levels versus time were measured in a group of 10 acute myocardial infarction (AMI) patients at our Intensive Care Unit. These patients were treated with single doses of 150 mg FLC as a 30-min intravenous infusion. Mean FLC plasma concentration values at 0, 1, 2, 4, and 8 h following administration were 562 +/- 271, 342 +/- 129, 270 +/- 90m, 240 +/- 80 and 210 +/- 60 ng/ml, respectively. Flecainide pharmacokinetics fitted an open two-compartment model, with a rapid distribution phase and a slow elimination phase. Mean values for the terminal plasma half-life (t1/2 beta) was 22.0 +/- 9.7 h and the volume of distribution (V beta) was 7.99 +/- 3.02 1/kg. FLC is different to other i.v. antiarrhythmics in having a prolonged plasma half-life which is a decided advantage. In contrast to lidocaine, FLC has a pharmacokinetic profile that enables it to be used for treating ventricular arrhythmia without constant-rate i.v. infusion and without the need for complicated loading dosages in order to avoid a 'pharmacokinetic dip' over the first hour of treatment.
Midazolam concentration curves versus time were analysed in 10 otherwise healthy patients (ASA I-II) with inferior limb pathologies. The benzodiazepine was used as an adjuvant agent to epidural anaesthesia in view of its lower residual effect compared with other intravenous benzodiazepines. Midazolam pharmacokinetics in these patients fitted an open two-compartment model. The plasma levels versus time corresponded to a biexponential process with a very rapid distribution phase (t1/2a = 5.7 +/- 2.4 min) and an elimination phase (t1/2 beta = 66 +/- 37 min). Mean values for distribution volumes in the central compartment and extrapolated values were Vc = 0.12 +/- 0.04 l/kg and V beta = 1.28 +/- 0.92 l/kg. This kinetic behaviour explains the rapid but short duration of midazolam action. The induction time, estimated from the start of hypnosis (eye closure), was from 60 to 120 s with i.v. injection. The duration of action for the dose administered was from 15 to 60 min, with plasma levels below 90 ng/ml upon eye opening.
Recent reports suggest that cyclosporin A is beneficial in inducing remission of idiopathic nephrotic syndrome. Nephrotic syndrome is seen in 10-30% of patients with rapidly progressive glomerulonephritis. We report a case of a 69-year-old man with nephrotic syndrome, associated with idiopathic rapidly progressive glomerulonephritis, who was treated initially with corticosteroid and cyclophosphamide. Three months later he developed thrombophlebitis and leucopenia and cyclophosphamide was suspended. Relapse of nephrotic syndrome associated with rapidly progressive glomerulonephritis developed and therapy with cyclosporin A was used with a good response.
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