High-presssure liquid chromatographic determination of methotrexate and its major metabolite, 7-hydroxymethotrexate, in human plasma

A rapid high-pressure liquid chromatographic assay is described for the analysis of methotrexate (MTX) and its major metabolite, 7-hydroxymethotrexate (7-OH-MTX), in plasma samples from patients following high-dose therapy. The method involves an ion-pair extraction of MTX from plasma with chromatography on a microparticulate anion-exchange column using ultraviolet detection at either 254 or 315 nm. Maximum sensitivity achieved was 1 X 10(-7) M. In addition to being specific for parent MTX, this procedure was used to detect and quantitate significant concentrations of 7-OH-MTX in several patients. Comparison to a protein-binding method indicated a greater degree of specificity for the chromatographic procedure. The procedure can be used to allow therapeutic monitoring of plasma MTX and metabolite for patients receiving high-dose MTX therapy as well as to determine the purity of formulations of MTX used clinically. In addition, the procedure is applicable to the support of pharmacokinetic studies of MTX in animals and man.

Immunological characteristics of a peroxidase protein in human neonatal cord serum

Adult serum haptoglobin-hemoglobin complexes exhibit acid-stable peroxidase activity. The haptoglobin level in human neonatal cord sera, however, is reported to be very low. We have isolated a protein from the cord sera of neonates, which has acid-stable peroxidase activity analagous to adult serum haptoglobins-haemoglobin complexes, but does not show any immunological identity to adult serum haptoglobins. It differs from the latter in its molecular size and electrophoretic mobility in agarose and polyacrylamide gels. It is unique to cord sera and it bears immunological identity to human IgG.

Ipsilateral blindness: a complication of carotid endarterectomy

We report on three patients in whom ipsilateral blindness developed following carotid endarterectomy. Fundoscopic examination of the retina documented ischemia and the visual field defects were permanent. In one patient, the internal carotid artery was patent and thought to be the conduit for embolization to the eye. Two patients had chronic occlusion of the internal carotid artery, and blindness resulted from atheromatous emboli to the eye through the external carotid artery in one and from postoperative thrombosis of the external cartoid artery in the other. Our experience calls attention to this infrequently reported complication of carotid endarterectomy and emphasizes the importance of the external carotid artery, especially when the internal carotid artery is occluded.

Pharmacokinetics in drug therapy II: Applications of clinical pharmacokinetics in the assessment of theophylline therapy

A patient case is presented to illustrate a systematic approach to the assessment and modification of theophylline therapy by the pharmacist using serum level analysis. The pharmacist is a pulmonary disease service is responsible for: (1) determining relevant aspects of the patient's clinical condition; (2) defining an initial theophylline administration regimen, including route, dose and schedule; (3) estimating expected theophylline levels based upon the regimen and known or assumed parameters of theophylline in the patient; (4) defining and recommending number and timing of serum samples to be drawn for analysis; (5) obtaining laboratory results and comparing with preliminary estimations; (6) assessing clinical response or toxicity, or both; and (7) recommending appropriate modifications in the theophylline regimen.

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.

Moral dilemmas in clinical cancer experimentation

An examination of certain moral tensions that have developed in clinical cancer experimentation is offered. It is argued that the individual partner must be addressed in his singular unique position, rather than as a potential for the future good.

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.