Determination of plasma and erythrocyte lithium concentrations by atomic absorption spectrophotometry

We describe a method for determining plasma and erythrocyte lithium concentrations by atomic absorption spectrophotometry. Plasma and hemolyzed whole-blood are diluted and analyzed, with use of a lithium hollow-cathode lamp, at 670.8 nm. Erythrocyte lithium concentrations are calculated indirectly from the hematocrit. The standard deviation for a 0.43 mmol/liter pool of whole blood, run daily over 11 months, was +/-20 mumol/liter (CV=5.1). The lithium concentration of a lyophilized pool assayed periodically over the same period (n=127) was 1.84+/-0.05 mmol/liter (CV=2.7%). The relatively low erythrocyte/plasma lithium ratio and the microhematocrit centrifugation force (9600 to 13 600 X g) make corrections for trapped plasma insignificant. Problems with matrix matching and viscosity are overcome by using a plasma pool standard for calculations. Values for erythrocyte lithium concentrations were unchanged in samples stored at room temperature up to 24 h. Hemolysis appears to be of possible clinical significance. This method is useful as a routine clinical laboratory procedure for monitoring patients with affective disorders, who are undergoing therapy with lithium.

Plasma and erythrocyte kinetic considerations in lithium therapy

Developments in the analysis and pharmacokinetics of lithium, and the role of the pharmacist in the management of lithium therapy in affective disorders, are described. Research showing that lithium levels in the brain may be better predicted from erythrocyte lithium levels than plasma levels is reviewed. Also reviewed is lithium kinetics in affective disorders. The pharmacist (1) determines relevant aspects of the patient's condition, (2) develops an appropriate blood sampling schedule, (3) initiates and maintains a serial lithium erythrocyte and plasma patient profile, (4) evaluates erythrocyte and serum levels in relation to established criteria to provide a basis for differential diagnosis of the patient, and (5) individualizes lithium dosage and schedules. Four cases are used to illustrate this approach. It is suggested that outpatient mental health clinics would be likely settings for the further development of this clinical role.

Delayed vein repositioning. A procedure for improving inadequate radial-cephalic arteriovenous fistulas

Patients undergoing hemodialysis, whose radial-cephalic arteriovenous fistulas (RCAVFs) were unsatisfactory because of poor accessibility, were treated by surgical repositioning of the full length of arterialized cephalic vein in the forearm. Marked improvement in accessibility for more than one year was achieved in 15 of 18 delayed venous repositioning operations. This procedure is recommended for improving certain types of inadequate RCAVF.

Rapid GLC determination of fusaric acid in biological fluids

A simple, sensitive GLC assay was developed for fusaric acid, the active metabolite of bupicomide, to follow the disposition of this investigational antihypertensive agent in patients undergoing therapy. Fusaric acid is efficiently extracted from biological samples, derivatized by on-column methylation, and chromatographed using flame-ionization detection. An internal standard is utilized to quantitate results. The procedure is rapid and specific for fusaric acid, and has a lower limit of sensitivity of 0.1 mug/ml. The method is suitable for supporting pharmacokinetic studies of bupicomide following therapeutic doses in animals and humans.

Plasma concentration of lidocaine after endotracheal spray

The rate of absorption and plasma concentrations of lidocaine were determined in 15 supine patients under general anesthesia following either endotracheal spray of 200 mg. (average 3.3 mg./kg.) of 4 percent lidocaine hydrochloride solution with a special cannula (LTA Kit, Abbott) (N = 6) or 1 mg./kg. of 2 percent lidocaine solution as an intravenous bolus injection (N = 9). In the 6 patients after endotracheal spray, peak plasma lidocaine levels were reached at 15 to 20 minutes (mean 3.54 plus or minus 0.76 S.E. mug./ml. at 20 minutes). In the 9 patients given 1 mg./kg. intravenously, dose peak concentrations were reached within 2 minutes (mean 5.63 plus or minus 0.18 S.E. mug./ml. at 2 minutes). Plasma concentrations of lidocaine in both groups were within nontoxic ranges.

Pharmacokinetics of cyclophosphamide in man

1. The pharmacokinetics of cyclophosphamide were investigated in cancer patients. The data can be characterized by a two-compartment open model. The half life of the elimination phase of the drug ranged between 3 and 11 hours.2. Extensive tubular reabsorption of the drug resulted in the excretion of only a small percentage of the administered dose. The mean renal clearance was 10.7 ml/minute.3. The calculated fraction of the dose of drug which was metabolized averaged 88%.