Lower phenytoin serum levels in persons switched from brand to generic phenytoin.

After generic phenytoin (PHT) was marketed, the authors identified eight adult patients (ages 34 to 49) whose seizures increased enough to require intervention after switching to generic PHT. The mean total PHT concentration on brand (before generic) was 17.7 +/- 5.3 mg/L, decreased to 12.5 +/- 2.7 mg/L with generic, and increased to 17.8 +/- 3.9 mg/L after brand was re-introduced. Brand and generic PHT do not yield equivalent concentrations in some patients and substitution should not be permitted without physician notification.

Rectal absorption of lamotrigine compressed tablets.

PURPOSE: Interruption of oral drug administration poses a significant clinical problem for antiepileptic drugs that have no parenteral formulation. If a drug is absorbed rectally, rectal administration can be a useful alternative when the oral route of administration is not possible. The purpose of this study was to compare the single-dose pharmacokinetics of lamotrigine (LTG) compressed tablets after rectal and oral administration in healthy volunteers. METHODS: A single LTG compressed tablet (100 mg) was administered orally and rectally to 12 volunteers in this single-dose, two-period, crossover study with a 2-week washout between doses. For rectal administration, tablets were crushed and suspended in 10 mL of water. Plasma samples were collected from 0 to 120 hr after each dose and analyzed for LTG by an HPLC method developed for this investigation. RESULTS: LTG plasma concentrations were lower after rectal administration versus oral administration. The average area under the curve was 28.90 +/- 9.5 microg/mL/hr after rectal administration and 51.71 +/- 19.2 microg/mL/hr after oral administration. The average maximum LTG concentration was 0.53 +/- 0.14 microg/mL after rectal administration and 1.45 +/- 0.35 microg/mL after oral administration. The relative bioavailability for LTG compressed tablets was 0.63 +/- 0.33 for rectal administration. There were no drug-related rashes or serious side effects. CONCLUSIONS: LTG suspension prepared from LTG compressed tablets is absorbed rectally, although not to the same extent or rate as when given orally.

Clinical laboratory estimations of serum and urinary phosphate.

Data from the 1977 College of American Pathologists (CAP) Chemistry Survey Program have been analyzed in order to evaluate currently used laboratory methods for determination of serum and urinary phosphate concentrations. The methods may be divided into those based on (1) molybdate and a reductant, (2) molybdate without a reductant (UV), (3) dye-binding, and (4) enzymatic (UV) assays. The majority of CAP Survey participants use a molybdate and reductant technic. Procedures using other reductants such as ferrous sulfate, ascorbate, and p-methylaminophenolsulfate manifest a slight positive bias. Compared to an overall mean concentration index, the SMAC-UV method manifests a considerable negative bias.

Glucose measurements. A 1977 CAP Survey analysis.

An anlysis of the 1977 College of American Pathologists (CAP) Comprehensive Chemistry Survey program for glucose measurements is presented. Based on average mean concentrations compared with all-method mean concentration, hexokinase methods are the most accurate. Glucose oxidase-oxygen rate methods demonstrate the best precision in interlaboratory comparison statistics. Neocuproine methods for glucose manifest unacceptable positive biases when compared with overall mean concentrations and other methods. Accuracy and precision indices for glucose measurements in urine are well below those obtained in serum. Again, redox methods, such as those based on neocuproine and ferricyanide, perform so poorly that they should be eliminated.

An interlaboratory comparison of serum total protein analyses.

An analysis of the 1976 CAP Comprehensive Chemistry Survey of total serum proteins is presented. More than 2,000 laboratories contributed data in this survey. Estimation of total serum protein concentration by the biuret reaction remains the most widely used technic, followed by refractometry. Precision and accuracy data for a number of analytic systems and methods are presented. Precisions for the entire group are nearly comparable. A negative bias for total protein concentration was shown by the SMAC.