[Analysis of the demand for detection of SARSCoV-2 in a health area of Spain]

OBJECTIVE

Since the discovery of the SARS-CoV-2 virus, the polymerase chain reaction technique (RT-PCR) has become the fundamental method for diagnosing the disease in its acute phase. The objective is to describe the demand-based series of RT-PCR determinations received at a Microbiology Service at a third-level reference hospital for a health area for three months spanning from the onset of the epidemic by SARS-CoV-2.

METHODS

A retrospective analysis of the total of the RT-PCR requested in the Microbiology Service analyzed from 02/25/2020 to 05/26/2020 (90 days) has been carried out. They have been grouped by epidemiological weeks and by the petitioner service. A descriptive analysis was carried out by age, gender and number of requests for each patient. In the tests carried out, a confidence level of 95% (p <0.05) was considered significant.

RESULTS

A total of 27,106 requests was received corresponding to 22,037 patients. Median age 53.7 (RIC 40.9-71.7) years, women: 61.3%. Proportion of patients with any positive RT-PCR: 14%. Of the total requests for RT-PCR, positive 3,710. Week 13 had the highest diagnosis performance (39.0%). The primary care has been the service thar has made the most requests (15,953). Patients with 3 or more RT-PCR: 565, of them, 19 patients had a positive result after previously having a negative one.

CONCLUSIONS

Requests have been increasing depending on the evolution of the epidemic. The RT-PCR has a high diagnostic performance in the phases of highest contagiousness and / or transmissibility of the virus.

Evaluation of an immunocapture-agglutination test (Brucellacapt) for serodiagnosis of human brucellosis

We evaluated the validity and the usefulness of a new test for the diagnosis of human brucellosis based on an immunocapture-agglutination technique. A total of 315 sera from 82 patients with a diagnosis of brucellosis, 157 sera from patients in whom brucellosis was suspected but not confirmed, and 412 sera from people living in rural areas with endemic brucellosis were studied. The seroagglutination test (SAT), Coombs anti-Brucella test, and Brucellacapt test were evaluated. All the initial sera from the 82 patients proved to be positive in Brucellacapt and Coombs tests, while only 75 (91.4%) were positive in the SAT. If a >/=1/160 diagnostic threshold titer was defined for the Brucellacapt test, Coombs test, and SAT, the sensitivities were 95.1, 91.5, and 65.8%, respectively. Taking the same diagnostic threshold titer for the 157 sera from the unconfirmed but suspected patients, the specificities of the Brucellacapt, Coombs, and SAT were 81.5, 96.2, and 100%, respectively; for the 412 control sera, the specificities were 99.0, 99.8, and 100%. The diagnostic efficiency (area below the receiver operating characteristic curve) of Brucellacapt was 0.987852 (95% confidence interval [CI], 0.95109 to 0.99286), very similar to the diagnostic efficiency of the Coombs test (0.97611; 95% CI, 0.94781 to 0.99146) and higher than that of SAT (0.91013; 95% CI, 0.86649 to 0.94317). The results of the Brucellacapt test were compared with those of the Coombs test (correlation coefficient, 0.956; P = 0.000) and SAT (correlation coefficient, 0.866; P = 0.000). The study shows very good correlation between the Brucellacapt and Coombs tests, with a high concordance between titers obtained in the two tests. Nevertheless, lower correlation and concordance were found between the Brucellacapt and Coombs tests when the results for titers of >/=1/160 were compared (0.692; P = 0.000). In acute brucellosis, the Brucellacapt and Coombs tests render positive titers of >/=1/160. When the titers are lower, they increase significantly in the following 30 days, despite the evolution of SAT titers. In contrast, Brucellacapt and Coombs titers are always high (>/=1/640) in brucellosis with long evolution, whether SAT titers are higher or lower than 1/160.

Gossypol treatment of recurrent adult malignant gliomas

Gossypol, a polyphenolic compound which depletes cellular energy by inhibition of several intracellular dehydrogenases, has been shown to have antiproliferative activity against human glial tumor cell lines in vitro and in nude mouse xenografts. Human trials of gossypol as a male contraceptive have demonstrated safety of long-term administration. We studied the activity of Gossypol 10 mg PO bid in 27 patients with pathologically confirmed glial tumors which had recurred after radiation therapy. Fifteen patients had glioblastoma, 11 patients anaplastic astrocytoma, 1 patient relapsed low grade glioma. Response was assessed every 8 weeks using CT/MRI scan and clinical criteria including decadron requirement. Treatment was continued until disease progression. Two patients had partial response (PR); 4 had stable disease for 8 weeks or more. One patient maintained a PR with improved KPS for 78 weeks. The other had a PR lasting 8 weeks. Toxicity was mild: 2 heavily pretreated patients had mild thrombocytopenia, 5 patients developed hypokalemia, 3 patients developed grade 2 hepatic toxicity and peripheral edema. Gossypol levels measured by HPLC did not correlate with response or toxicity in this study. We conclude that gossypol is well tolerated and has a low, but measurable, response rate in a heavily pretreated, poor-prognosis group of patients with recurrent glioma. The presumed novel mechanism of action, lack of significant myelosuppression, and activity in patients with advance glioma support further study of gossypol as an antineoplastic agent.

[Genotypes of hepatitis C virus: their relationship with risk factors, the severity of liver disease, and the serologic response]

BACKGROUND

The objective of our study was to ascertain the prevalence of different HCV genotypes between the hepatitis C patients in the health area of Monforte de Lemos, Spain, as well as the possible influence of risk factors on their distribution and their relation with hepatic disease and with the serologic response.

PATIENTS AND METHODS

We have studied 128 patients with hepatitis C. Of these, 41 were intravenous drug users (IVDU), 19 had received transfusions, 7 were hemodialyzed and in 61 the risk factors were unknown. Antibodies against HCV were detected by second-generation enzyme immunoassay (EIA) and confirmed by immunoblot. RNA-HCV presence was studied by reverse transcription-PCR (RT-PCR), and a reverse hybridization test of the amplifications was used for the genotyping.

RESULTS

Hepatitis C genotypes 1b (46.1 [8.6%]), 1a (23.4 [7.3%]) and 3a (13.3 [5.9%]) were the most frequently encountered genotype. Genotype 1a (48.8 [15.3%]) was the most prevalent genotypes in IVDU patients, while 1b was the most frequent in patients of unknown risk factors (62.3 [12.1%]). Alanine-aminotransferase (ALT) was elevated in 66.6 (17.7%) of patients with genotype 1a, in 87.5 (8.6%) of patients with genotype 1b (p = 0.0367) and in 94.1 (11.2%) of patients with genotype 3a (p = 0.0347). Subtype 1b was present in 6 of 7 cases of cirrhosis (85.7%) and in 7 of 12 cases of active chronic hepatitis (58.3%). No significant statistical differences were observed between the genotypes and the specific IgM response against core antigen of HCV, neither we observed differences in the serologic response against C1, C2, NS3 and NS4 peptides.

CONCLUSIONS

Hepatitis C genotypes 1a and 3a were the most prevalent genotypes between IVDU patients while genotype 1b was the most frequent between non-IVDU patients. Genotype 1b was associated to severe liver disease. Percentage of positivity or the reactivity against HCV peptides was independent of the genotype encountered in the patient.

[Variants of hepatitis C virus in different risk groups. Comparative study of a method for genotyping and another for serotyping]

AIMS

The aim of this study was to know the prevalence of the different variants of HCV in the Health Care area of Monforte de Lemos (Lugo, Spain) and its distribution according to risk factors and to compare the results obtained with one genotyping and one serotyping technique.

PATIENTS AND METHODS

Eighty-four patients with hepatitis C were studied, 25 of whom were IVDA, 14 had received blood transfusions, 4 hemodialysis and the risk factor was unknown in 41. The antibodies against HCV were studied by second generation EIA and confirmed by an immunoblot technique. Serotyping was carried out by an ELISA test. Genotyping was undertaken with a reverse hybridation test of the amplification obtained by polymerase chain reaction prior to reverse transcription (RT-PCR).

RESULTS AND CONCLUSIONS

The genotypes most frequently observed were 1b (47.6%), 1a (20.2%) and 3 (14.3%). In the IVDA patients the genotypes 1a (40%) and 3 (24%) predominated. The 1b genotype was the most prevalent in the patients of unknown risk (68.3%) and patients with a history of blood transfusion (50%). The prevalence of the different serotypes was similar to that of the corresponding genotypes, with nearly 100% agreement. The number of untypable cases was greater in the serotyping technique (20.2%) than in the genotyping (2.4%). A greater number of mixed infections was detected with serotyping (7 cases, 8.3%) than with genotyping (1 case, 1.2%). Lesser sensitivity of the serotyping test was observed in the patients lacking anti-NS4 antibodies.

Inhibition of 11 beta-hydroxysteroid dehydrogenase obtained from guinea pig kidney by furosemide, naringenin and some other compounds

Inhibition of 11 beta-hydroxysteroid dehydrogenase (11 beta-OHSD) can cause excess mineralocorticoid effects and hypokalemia. Several substances causing hypokalemia (glycyrrhizic acid in licorice and gossypol) inhibit this enzyme. We tested other compounds for activity to inhibit 11 beta-OHSD in guinea pig kidney cortex microsomes with NADP as cofactor and cortisol as substrate. Furosemide was an inhibitor while bumetanide was not, indicating a mechanism for the increase K+ excretion caused by furosemide compared with bumetanide. Naringenin (found in grapefruit juice), ethacrynic acid, and chenodeoxycholic acid had inhibitor IC50 values similar to glycyrrhizic acid. We conclude that various compounds can inhibit this enzyme and may play a role in K+ metabolism and adrenocorticosteroid action.

Acetylation phenotypes and environmental chemical exposure of people with idiopathic systemic lupus erythematosus

OBJECTIVE

To test the hypotheses that there is an excess percentage of slow acetylators among patients with idiopathic systemic lupus erythematosus (SLE) and that these patients had excessive exposure to environmental amines and hydrazines before the onset of illness.

METHODS

Case-control study with structured interview and acetylation phenotyping.

RESULTS

No excess proportion of slow acetylators or environmental amine exposure was found.

CONCLUSION

Slow acetylation phenotype and exposure to environmental amines are not principal causes of idiopathic SLE.

Oral gossypol in the treatment of metastatic adrenal cancer

Medical treatment of metastatic adrenal cancer is largely unsuccessful and has considerable toxicity. We previously demonstrated the activity of the plant toxin gossypol against human adrenal cancers in nude mice. We therefore examined the efficacy and toxicity of oral gossypol as a treatment for adrenal cancer in humans. Twenty-one patients with metastatic adrenal cancer received oral gossypol at doses of 30-70 mg/day. Patients were monitored for side effects of gossypol, changes in hormone secretion, and tumor response. Eighteen patients completed at least 6 weeks of gossypol treatment. Three of these patients, whose tumors were refractory to other chemotherapeutic agents, had partial tumor responses (> or = 50% decrease in tumor volume) that lasted from several months to over 1 yr. One patient had a minor response followed by resection of her remaining disease, 1 patient had stable disease, and 13 patients had disease progression. Three patients died of their disease without receiving sufficient gossypol to achieve detectable drug levels, and were eliminated from the final analysis. The side effects of gossypol were generally well tolerated; the only serious side effect was abdominal ileus that resolved when the drug was temporarily withheld and restarted at a lower dose. We conclude that oral gossypol can be used relatively safely on an outpatient basis for the treatment of metastatic adrenal cancer. The response rate is similar to the other agents currently available for adrenal cancer, and responses were seen in patients who had failed other chemotherapeutic regimens. This study provides the first indication that gossypol may have activity against cancer in humans, suggesting the need for further investigation of gossypol as an antitumor agent.

Differences in serum potassium concentrations in normal men in different geographic locations

Hypokalemia has been associated with the taking of gossypol, a potential oral antifertility drug for men. Because the frequency of this response differed in different parts of the world, this study was done to learn if "normal" serum [K+] also differed. [K+] was measured by flame photometry in serum from apparently normal men from Austria (n = 30), China (53), Brazil (100), the Dominican Republic (38), and the US (103), and in plasma from Nigerian men (82). The mean (SD) for [K+] in Chinese men, 3.82 (0.27) mmol/L, was lower than that in Brazilians [4.06 (0.29) mmol/L], Austrians [4.14 (0.44) mmol/L], Dominicans [4.37 (0.33) mmol/L], or Americans [4.38 (0.37) mmol/L]. Apparently there are regional differences in average serum [K+], with men in China having lower serum [K+] than men elsewhere. This may predispose them to hypokalemia.

Differences in serum potassium concentrations in normal men in different geographic locations

Hypokalemia has been associated with the taking of gossypol, a potential oral antifertility drug for men. Because the frequency of this response differed in different parts of the world, this study was done to learn if "normal" serum [K+] also differed. [K+] was measured by flame photometry in serum from apparently normal men from Austria (n = 30), China (53), Brazil (100), the Dominican Republic (38), and the US (103), and in plasma from Nigerian men (82). The mean (SD) for [K+] in Chinese men, 3.82 (0.27) mmol/L, was lower than that in Brazilians [4.06 (0.29) mmol/L], Austrians [4.14 (0.44) mmol/L], Dominicans [4.37 (0.33) mmol/L], or Americans [4.38 (0.37) mmol/L]. Apparently there are regional differences in average serum [K+], with men in China having lower serum [K+] than men elsewhere. This may predispose them to hypokalemia.

Inhibition of 11 beta-hydroxysteroid dehydrogenase by gossypol and bioflavonoids

The enzyme 11 beta-hydroxysteroid dehydrogenase (11 beta-OHSD) oxidizes hydrocortisone to inactive cortisone in the kidney and is an important regulator of renal K+ clearance. Gossypol, in clinical trials as an antifertility drug for men in China, was associated with episodes of hypokalemia. To learn whether gossypol and other structurally similar compounds in plants can inhibit 11 beta-OHSD activity, purified enzyme from rat liver and in human renal cortical microsomes was studied. Rat liver enzyme was inhibited by glycyrrhetinic acid > gossypol >> morin > quercetin >> rutin. Glycyrrhetinic acid, gossypol, and morin inhibited activity of the human kidney enzyme. Enzyme in microsomes from five human kidneys had an IC50 (S.D.) of 1.5 (1.2) mumol/L for glycyrrhetinic acid; enzyme in microsomes from six human kidneys had a 50% inhibitory doses of 147 (25) mumol/L for gossypol. Our observations indicate that gossypol and other compounds in plants can inhibit 11 beta-OHSD activity and may thereby increase K+ excretion.

Inhibitory effects of gossypol on corticosteroid 11-beta-hydroxysteroid dehydrogenase from guinea pig kidney: a possible mechanism for causing hypokalemia

Inhibition of 11-beta-hydroxysteroid dehydrogenase (11-beta-OHSD) in the kidney can cause excess mineralocorticoid effect and hypokalemia. To find out if gossypol, a potential oral contraceptive for men that has been associated with cases of hypokalemia, inhibits this enzyme, its effect on guinea pig kidney was studied. Working with microsomes from the kidney cortex, and using corticosterone as the substrate, racemic gossypol was found to be a competitive inhibitor of 11-beta-OHSD with a Ki of 67 +/- 5 microM. The (+) enantiomer was a little more potent than the (-) enantiomer. Microsomes from the kidneys of animals given gossypol for 2 weeks had lower enzyme activities than saline-treated animals. Microsomes from a strain of hairless guinea pigs had lower intrinsic enzyme activity than the normal animals. We conclude that there is genetic variation in the activity of this enzyme and that it can be inhibited by gossypol.

Hydromorphone levels and pain control in patients with severe chronic pain

To better understand the use of narcotic analgesics, the hydromorphone concentration was measured in serum samples from 43 patients with chronic severe pain who were receiving this drug. At the time of blood sampling, pain intensity, mood, and cognitive performance were assessed. There was large individual variation in the dose-drug level relationship. Seven patients with bone or soft tissue pain and drug levels of greater than or equal to 4 ng/ml had good pain control, whereas 10 did not. None of 15 patients with levels less than 4 ng/ml had pain control, despite drug doses similar to those given patients with higher levels. Thus 60% of the patients without control of their pain had hydromorphone levels below the lowest level that produced pain control. No patient with pain from nerve infiltration or compression had good pain control, irrespective of the drug level or dose. Poor mood correlated with high pain intensity and low drug level. Impaired cognitive performance was not related to drug level. Knowing that there is a low concentration of narcotic in the blood of a patient with chronic severe pain who is receiving high drug doses and who shows lack of both efficacy and side effects may reassure health care professionals that further narcotic dosage escalation is appropriate.

Pharmacokinetics of pentobarbital enantiomers as determined by enantioselective radioimmunoassay after administration of racemate to humans and rabbits

Radioimmunoassays were developed for R- and S-pentobarbital. The optical isomers of pentobarbital were individually alkylated to N-crotonic acid analogs that were coupled to bovine serum albumin. Immunization of rabbits with the conjugates, which were enantiomerically pure at the asymmetric' carbon of the pentobarbital moiety, led to formation of antisera that selectively bound the predicted enantiomer. In displacement studies with enantiomerically pure radioligands, the opposite enantiomer showed 1.0 to 1.4% cross-reaction. Similar selective binding was observed for enantiomers of secobarbital, thiopental and thiamylal. Assays were developed and used to determine enantiomer pharmacokinetics in rabbits and humans given racemic pentobarbital. In rabbits, difference in clearance of the two isomers was minimal, the result of a slightly larger volume of distribution of the R-enantiomer combined with a slightly higher value of the elimination rate constant beta for the S-enantiomer. In humans, the volume of distribution was 12% greater for the R-enantiomer, but the value of beta was 14% higher for this isomer as well. Thus, the median clearance of the S-enantiomer (1.96 liters/h) was 25% less than that of the R-isomer (2.58 liters/h). The S-enantiomer was also more strongly protein bound in plasma (73.5% vs 63.4% for the R-enantiomer), which is consistent with its structural congruence to S-warfarin, S-phenprocoumon and S-glifumide.

Plasma levels, protein binding, and elimination data of lidocaine and active metabolites in cardiac patients of various ages

The serum and urine levels of lidocaine and two active dealkylated metabolites, monoethylglycinexylidide (MEGX) and glycinexylidide (GX), were determined by HPLC in 33 cardiac patients receiving lidocaine for more than 1 day. Clinical assessment of nervous system toxicity was carried out at the time of blood drawing. The ratios in serum of MEGX to lidocaine and of GX to lidocaine were 0.36 +/- 0.26 (mean +/- SD) and 0.11 +/- 0.11. Lidocaine and MEGX binding to serum proteins from seven patients 2 days after their myocardial infarctions were 55.4 +/- 5.9% and 14.3 +/- 3.0%. After correction for this difference in protein binding, the MEGX/lidocaine ratio in serum water was 0.68 +/- 0.49. MEGX levels in serum water were 80% or more of the lidocaine levels in 11 of the 33 patients. GX binding was 5 +/- 4%. Even after correction for protein-binding differences, GX levels in serum water were low compared to lidocaine levels. The steady-state serum GX concentration normalized for lidocaine infusion rate declined with age. Of 27 patients without toxicity, six had serum lidocaine levels above 8 micrograms/ml. Five of six patients with toxicity had levels less than 8 micrograms/ml. The renal clearance of lidocaine, MEGX, and GX was less than creatinine clearance in most patients. We conclude that MEGX, but not GX, contributes to the pharmacologic activity of lidocaine therapy in a substantial fraction of patients. We also suggest that the concept of a single value for the upper limit of the therapeutic level of lidocaine in serum is an oversimplification because it does not take into account individual differences in drug-protein binding or accumulation of active metabolites.

Microsomal hydroxylation as measured by pentobarbital elimination in patients with idiopathic systemic lupus erythematosus

A mechanism postulated for drug- or chemical-induced systemic lupus erythematosus (SLE) is that the chemical is covalently bound to nuclear macromolecules increasing the immunogenicity of the macromolecule. This may require metabolic activation by oxidation. There are many similarities between drug-induced and idiopathic SLE. Twelve patients with idiopathic SLE and 12 normal subjects were given 100 mg pentobarbital orally to evaluate their microsomal hydroxylating activity. Plasma pentobarbital concentration was measured by gas-liquid chromatography. Mean plasma pentobarbital half-life was 24 +/- 10 (mean +/- SD) hr in the SLE patients, which is only slightly shorter than the 26 +/- 12 hr in the control subjects. The mean apparent volume of distribution in the patients was 1.28 +/- 0.30 l/kg, which is slightly above the 1.00 +/- 0.37 l/kg in the normal subject (P less than 0.05). Mean metabolic clearance rate in the SLE patients was 0.045 +/- 0.022 l/hr/kg, which is more than the 0.028 +/- 0.008 l/hr/kg in the normal control subjects (P less than 0.02). Since the metabolic clearance rate of a drug is the proper value for evaluating metabolism rate, we conclude that patients with SLE hve an increased elimination rate for drugs or other foreign compounds that are biotransformed by microsomal oxidation and may more rapidly bioactivate chemicals to reactive compounds.

Age and renal clearance of cimetidine

In 35 patients (ages 20 to 86 yr) receiving cimetidine therapeutically two serum samples and all urine formed in the interim were collected for analysis of cimetidine by high-pressure liquid chromatography and for creatinine. Cimetidine clearance decreased with age. The extrapolated 6-hr serum concentration of cimetidine per unit dose, after intravenous cimetidine, increased with age of the patients. The ratio of cimetidine clearance to creatinine clearance (Rc) averaged 4.8 +/- 2.0, indicating net tubular secretion for cimetidine. Rc seemed to be independent of age and decreased with increasing serum concentration of cimetidine, suggesting that secretion of cimetidine is a saturable process. There was only one case of dementia possibly due to cimetidine (with a drug level of 1.9 microgram/ml 6 hr after a dose) in a group of 13 patients without liver or kidney disease who had cimetidine levels above 1.25 microgram/ml. Thus, high cimetidine levels alone do not always induce dementia.

Improved method for the measurement of cimetidine in human serum by reverse-phase high-pressure liquid chromatography

An improved method for the measurement of cimetidine in human serum by reverse-phase HPLC has been developed. The assay involves the addition of the following to 1.0 ml serum: 5 ml of ethyl acetate/isopropanol (96:4 by volume); 0.1 ml of 5N NaOH; and 0.1 ml of the internal standard, N-cyano-N'-methyl-N"-[3-(4-imidazolyl)propyl]-guanidine, which is a close structural analog of cimetidine. The extracted cimetidine is quantitated with high-pressure liquid chromatograph containing a reverse-phase column and a variable-wavelength UV detector (228 nm). The mobile phase consists of methanol in 5 mM K2HPO4 (adjusted to pH 2.8) as a 10:90 mixture by volume. At a flow rate of 2 ml/min, the retention times for the internal standard and cimetidine are 2.8 and 6.2 min, respectively. The standard curve for cimetidine is linear from 0.1 at least 4.0 micrograms/ml in serum. The CV of this assay for cimetidine, obtained from analysis of six replicate samples of a 1.0 microgram/ml serum pool, is 2%. The CV of this method obtained from the daily analysis (N = 12) of the 1.0 microgram/ml cimetidine standard, is 3%, and that from the 0.5 microgram/ml standard is 5%. Cimetidine was found to be stable in refrigerated or frozen serum for 1 month and in whole blood for 24 hr either at room temperature or refrigerated. In the serum from 13 patients receiving cimetidine therapy, the trough cimetidine levels varied from less than 0.1 to 2.7 mg/ml.

Liquid chromatography and fluorescence spectroscopy compared with a homogeneous enzyme immunoassay technique for determining quinidine in serum

Sera from 67 cardiac patients being treated with quinidine were analyzed for this drug by both a homogeneous enzyme immunoassay (EMIT) and a fluorescence procedure (double-extraction method). Of these samples, 47 were also analyzed for quinidine and its major metabolite in serum, (3s)-3-hydroxyquinidine, by liquid chromatography. Results by the EMIT procedure correlated well with those by both the chromatographic and fluorescence procedures, but EMIT gave, on the average, 25% higher values for quinidine than did the chromatographic procedure. The EMIT procedure is therefore not totally specific. (3s)-3-Hydroxyquinidine and dihydroquinidine (a contaminant present in standard quinidine formulations) each show cross reactivity in the EMIT assay for quinidine. Nevertheless, the EMIT assay for quinidine is acceptable for clinical use because these two compounds are also pharmacologically active.

Liquid chromatography and fluorescence spectroscopy compared with a homogeneous enzyme immunoassay technique for determining quinidine in serum

Sera from 67 cardiac patients being treated with quinidine were analyzed for this drug by both a homogeneous enzyme immunoassay (EMIT) and a fluorescence procedure (double-extraction method). Of these samples, 47 were also analyzed for quinidine and its major metabolite in serum, (3s)-3-hydroxyquinidine, by liquid chromatography. Results by the EMIT procedure correlated well with those by both the chromatographic and fluorescence procedures, but EMIT gave, on the average, 25% higher values for quinidine than did the chromatographic procedure. The EMIT procedure is therefore not totally specific. (3s)-3-Hydroxyquinidine and dihydroquinidine (a contaminant present in standard quinidine formulations) each show cross reactivity in the EMIT assay for quinidine. Nevertheless, the EMIT assay for quinidine is acceptable for clinical use because these two compounds are also pharmacologically active.

Prevalence of high (3S)-3-hydroxyquinidine/quinidine ratios in serum, and clearance of quinidine in cardiac patients with age

In the sera from 42 patients receiving quinidine, (3S)-3-hydroxyquinidine (3-OH), an active metabolite of quinidine, and quinidine were determined by high-pressure liquid chromatography with fluorescence detection. These results were added to those of 25 other patients reported previously. The 3-OH/quinidine ratio averaged 0.34 +/- 0.17 (SD) with a range of 0.10 to 0.90. Eleven patients (16%) had ratios above 0.50. After adjusting for protein binding differences between the 2 compounds, these 16% had 3-OH concentrations in serum water greater than that of quinidine. An additional 7 patients (10%) of the total) had levels of this metabolite in serum water slightly less than that of quinidine. A histogram showing the frequency distribution of 3-OH/quinidine in serum indicates extensive skewing with possibly a bimodal distribution with the antimode at 0.50. Thus, 3-OH may make a significant contribution to the effect of quinidine therapy in a fraction of treated patients. The clearance of quinidine decreased with age, indicating the need for, on the average, higher doses of quinidine in the young.

Fluorometric screening method for detecting benzodiazepines in blood and urine

We report a fluorometric method for detecting diazepam, chlordiazepoxide, oxazepam, chlorazepate, and (or) their major metabolites in blood, urine, or gastric contents at low therapeutic concentrations. The drugs are first hydrolyzed to their respective benzophenones and converted to highly fluorescent 9-acridanones. Total benzodiazepines (parent plus metabolites) in blood and gastric contents are semiquantitatively evaluated and compared to results of gas-chromatographic determinations.