Second derivative ultraviolet spectrophotometry and HPTLC for the simultaneous determination of vitamin C and dipyrone.

Two accurate, precise and sensitive thin layer chromatographic (TLC) and second derivative UV-spectrophotometric procedures are described for the simultaneous determination of ascorbic acid and dipyrone in pure form and in pharmaceutical dosage forms. The TLC method involved direct application of methanolic solutions of tested samples on silica gel TLC plates using water:methanol (95:5 v/v) as developing system. The developed plates were then directly scanned at 260 nm using a TLC scanner. The second method depends on second derivative UV-spectrophotometry with zero crossing technique of measurement. Second derivative amplitudes at 280 and 272 nm were selected for the determination of ascorbic acid and dipyrone, respectively. Both methods show good linearity, precision and reproducibility. They are simple and do not require manipulation prior to analysis. The proposed methods have been successfully applied to the determination of the drugs in various pharmaceutical dosage forms such as tablets and ampoules.

Acetylation of dapsone by human whole blood.

We studied the acetylation of dapsone (DDS) in vitro by whole blood taken from subjects with known acetylator phenotype. The acetylation of DDS by whole blood was both incubation time- and DDS concentration-dependent. Thus, it is highly recommended to separate plasma immediately after blood withdrawal during acetylation phenotyping using DDS. para-aminobenzoic acid (PABA) substantially inhibited the acetylation of DDS by whole blood taken from both slow and rapid acetylators, while procainamide (PAD) significantly inhibited DDS acetylation by whole blood taken from slow acetylators. At the highest PAD concentration used (208 microM), DDS acetylation by whole blood taken from rapid acetylators was also inhibited. In contrast, sulphanilamide (SAD) failed to produce any significant inhibition of the acetylation of DDS by whole blood taken from either slow or rapid acetylators. Furthermore, there was no correlation between DDS acetylation by whole blood in vitro and the acetylator status of the subject. It is therefore not possible to predict the acetylator phenotype by studying DDS acetylation by human whole blood. These results indicate that the DDS N-acetyltransferase of human whole blood is most probably of the monomorphic type.

Simultaneous determination of theophylline and guaiphenesin by third-derivative ultraviolet spectrophotometry and high-performance liquid chromatography.

Two methods are described for the simultaneous determination of theophylline and guaiphenesin in combined pharmaceutical dosage forms. The first method depends on third-derivative ultraviolet spectrophotometry, with the zero crossing technique of measurement. Third-derivative amplitudes at 222 and 278 nm were selected for the assay of guaiphenesin and theophylline, respectively. The second method is based on high-performance liquid chromatography on a reversed-phase column using a mobile phase of 0.01 mol dm-3 sodium dihydrogen phosphate-methanol-acetonitrile (8 + 2 + 1) (pH 5.5) with detection at 245 nm. Both methods showed good linearity, precision and reproducibility. The proposed methods were successfully applied to the determination of these drugs in laboratory-prepared mixtures and in capsules or elixir.

Acetylator phenotypes of Jordanian diabetics.

The acetylator phenotype was determined in 31 insulin-dependent (IDDM) and 110 noninsulin-dependent (NIDDM) Jordanian diabetics, and was compared to that of 160 healthy volunteers of the same ethnic group. Dapsone was used as the test drug. The rapid acetylator phenotype was slightly less frequent in IDDM and slightly more frequent in NIDDM. Neither of the differences was significant. When acetylator status in the two types of diabetes mellitus was compared, there was a significant difference among the two groups. Patients with IDDM had a higher percentage of the slow acetylator phenotype when compared to NIDDM patients. The association between acetylator status and IDDM in Jordanians, which agrees with that reported for the Saudi Arabian population, is the reverse of what is found in European populations. The results demonstrate ethnic differences in acetylator status among IDDM patients.

N-acetylation phenotyping using dapsone in a Jordanian population.

1. The N-acetylation of dapsone (DDS) was studied in 160 unrelated healthy Jordanian volunteers. 2. The frequency of slow acetylators determined using the plasma monoacetyldapsone (MADDS) to DDS ratio (MADDS/DDS), was 67.5% with a 95% confidence interval of 59 to 76%. Slow acetylators had an acetylation ratio of less than 0.42. 3. Applying the Hardy-Weinberg Law, the frequency of the recessive allele controlling slow acetylation was found to be 0.82 +/- 0.02. 4. The frequency distribution histogram of the plasma MADDS/DDS ratio showed an apparent trimodal pattern. The number of homozygous (n = 16) and heterozygous (n = 36) rapid acetylators derived from the observed data did not agree with those predicted for the respective rapid acetylators (n = 5 and n = 47) according to the Hardy-Weinberg Law. The suggested antimode used to discriminate the two groups was 0.82. 5. The mean plasma concentration of MADDS and the mean plasma acetylation ratio were about three times lower in slow than in rapid acetylators. However, there was no difference in mean plasma DDS concentration between slow and rapid acetylators. 6. There was a significant correlation (r = 0.853, P less than 0.001) between plasma MADDS concentration and the acetylation ratio. For DDS such a correlation was absent (r = 0.059, P = 0.23).

Simultaneous high performance liquid chromatographic determination of dapsone and monoacetyldapsone in human plasma and urine.

A rapid, specific and a one-stage protein precipitation method for simultaneous estimation of dapsone (DDS) and monoacetyldapsone (MAD) concentration in plasma and urine using high performance liquid chromatography (HPLC) is described. The applicability of the method for monitoring DDS and MAD blood levels in two different acetylator phenotype volunteers following the administration of 100-mg oral dose of DDS was shown. Cumulative urinary excretion of DDS and MAD were studied in the same volunteers.

Simultaneous high-pressure liquid chromatographic analysis of ampicillin and cloxacillin in serum and urine.

A rapid, specific and sensitive high pressure liquid chromatographic (HPLC) assay for the simultaneous determination of ampicillin and cloxacillin in serum and urine is developed. Ampicillin, cloxacillin and cephalexin (internal standard) were eluted from a 6.5 mu Synchropack RPP reversed phase column at ambient temperature using a mobile phase comprised of methanol:water (3/7v/v) and containing 0.011 M sodium-n-octane sulphonate, 0.005 M NaH2PO4 and 1.3% v/v of 0.5 M HCl (pH 2.7). The analysis time required no longer than 11 min. Equations are presented for the linear relationships between the peak height ratios of ampicillin/cephalexin and cloxacillin/cephalexin over the range 10-80 micrograms/ml (ampicillin) and 5-25 micrograms/ml (cloxacillin), respectively. The sensitivity limits for ampicillin and cloxacillin in serum and urine were 5 micrograms/ml and 1 microgram/ml, respectively. Quality criteria such as accuracy, precision and specificity were studied extensively. We investigated the applicability of the HPLC assay for the developed simultaneous determination of the cumulative amounts of ampicillin and cloxacillin, excreted unchanged in urine after an oral dose containing 500 mg ampicillin and 500 mg cloxacillin to a human volunteer.

Utility of iodine and 7,7,8,8-tetracyanoquinodimethane for determination of terfenadine.

Simple and sensitive spectrophotometric methods for the assay of terfenadine are described. The first is based on the reaction of terfenadine with iodine to give a molecular charge-transfer complex, the terfenadine acting as an n-electron donor and iodine as a sigma-electron acceptor. The second depends on the formation of a highly coloured stable radical anion between terfenadine and 7,7,8,8-tetracyanoquinodimethane (TCNQ) as a pi-electron acceptor. Beer's law is obeyed over the terfenadine concentration range 0.2-1.2 mg/100 ml. The proposed methods have been successfully applied to the analysis of commercial terfenadine tablets.