Determination of the contamination by azole antimycotics in hospital and house sewage - a pilot project for the city of Dresden

Medicininal compounds and their metabolites are known to end up in sewerage and may slip through the cleaning process. Azole antimycotics are frequently used in hospitals, in particular for patients with cancer or immunosuppression. The aim of the study was to determine whether measurable azole antimycotic concentrations were introducted in the sewarage drain of an acute care hospital with special interest in oncology and hematology and the extent of removal of antimycotics by the sewerage treatment plant. For this, the concentrations of three commonly used azole antimycotics were measured in the effluent of the sewerage drain at the University Hospital Dresden, as well as in the influent and effluent of the main sewerage treatment plant of the city. To extrapolate the theoretical influent to the sewerage treatment plant, prescription from the regio`s main health insurance the AOK Sachsen and the hospital consumption data were used. Measurable concentrations were obtained for fluconazole and ketoconazole in the influent and effluent of the sewerage treatment plant. Voriconazole's concentrations were under the lower limit of quantification. To determine the azole clearance of the treatment plant a sludge sample was investigated. Sufficient clearance was detected for ketoconazole but not for fluconazole. The consumption and prescription rates were collected and correlated with the measured concentrations. In result, only fluconazole's concentrations provided a good match with the prescription and consumption data.

Meeting the challenge of interpreting high-resolution single nucleotide polymorphism array data in prenatal diagnosis: does increased diagnostic power outweigh the dilemma of rare variants?

OBJECTIVE

Several studies have already shown the superiority of chromosomal microarray analysis (CMA) compared with conventional karyotyping for prenatal investigation of fetal ultrasound abnormality. This study used very high-resolution single nucleotide polymorphism (SNP) arrays to determine the impact on detection rates of all clinical categories of copy number variations (CNVs), and address the issue of interpreting and communicating findings of uncertain or unknown clinical significance, which are to be expected at higher frequency when using very high-resolution CMA.

DESIGN

Prospective validation study.

SETTING

Tertiary clinical genetics centre.

POPULATION

Women referred for further investigation of fetal ultrasound anomaly.

METHODS

We prospectively tested 104 prenatal samples using both conventional karyotyping and high-resolution arrays.

MAIN OUTCOME MEASURES

The detection rates for each clinical category of CNV.

RESULTS

Unequivocal pathogenic CNVs were found in six cases, including one with uniparental disomy (paternal UPD 14). A further four cases had a 'likely pathogenic' finding. Overall, CMA improved the detection of 'pathogenic' and 'likely pathogenic' abnormalities from 2.9% (3/104) to 9.6% (10/104). CNVs of 'unknown' clinical significance that presented interpretational difficulties beyond results from parental investigations were detected in 6.7% (7/104) of samples.

CONCLUSIONS

Increased detection sensitivity appears to be the main benefit of high-resolution CMA. Despite this, in this cohort there was no significant benefit in terms of improving detection of small pathogenic CNVs. A potential disadvantage is the high detection rate of CNVs of 'unknown' clinical significance. These findings emphasise the importance of establishing an evidence-based policy for the interpretation and reporting of CNVs, and the need to provide appropriate pre- and post-test counselling.

Distribution of metoprolol in human autopsy material

In forensic medicine autopsy material is primarily investigated to find out the cause of death. But the results of corresponding toxicology measurements often involve more information. With screening methods drugs were detected not being related to the cause of death. Liquid/liquid extraction and LC/MS/MS methods were used for the determination of drug concentrations. In seven cases metoprolol could be determined in different autopsy materials. In all cases the dosage of the drug was unknown. In cases with oral application probably the patients took a normal customary continuous dosage. Intoxication with metoprolol could be excluded in all cases. The concentrations of metoprolol in blood were all in the therapeutic range. The time between oral intake and death was unknown. Therefore and because of the low number of cases statistic calculations were not meaningful and an individual case study was necessary. In three cases the highest concentration of metoprolol was found in the liver. Probably, metoprolol was taken shortly before the person died. In the other cases the highest concentration of metoprolol was found in urine. This means the elimination process of the drug predominated at the time of death. In all cases the concentrations of metoprolol were similar in the compartments heart blood, venous blood and brain. In this study it was possible to measure the distribution of metoprolol in human directly in several compartments. Measurement of drug concentrations in human autopsy material deepen the knowledge of its pharmacokinetics.

Determination of denaverine and its metabolites in urine samples by liquid chromatography-tandem mass spectrometry

A liquid chromatography-tandem mass spectrometric (LC-MS-MS) method was developed for the determination of the neurotropic-musculotropic spasmolytic agent denaverine and five of its metabolites in urine. In a first step beta-glucuronidase was used to cleave glucuronides in the human urine. After that samples containing denaverine and its phase I metabolites were extracted and cleaned up using an automated solid phase extraction method. An external calibration was used. The analytes were measured employing the multiple reaction-monitoring mode (MRM). The linear dynamic range for denaverine and its five metabolites determination was demonstrated from lower limit of quantification (8.0 ng/ml) to at least 500 ng/ml. The presented method is suitable for pharmacokinetic or toxicokinetic studies. With the help of reference substances some additional potential metabolites could be excluded in the urine samples. To look for additional unknown metabolites the LC-MS-MS system operated on one hand in the precursor ion mode using typical product ions of denaverine and of its metabolites and on the other hand in the product ion mode using postulated protonated molecules [M+H](+). With the help of the chromatographic behaviour and typical fragment ions of the unknown metabolites it was possible to elucidate their structures. Nine until now unknown metabolites were found in the urine samples. However, without reference substances a quantification of these analytes was not possible.

Induction of intestinal P-glycoprotein by St John's wort reduces the oral bioavailability of talinolol

St John's wort (SJW) is known to induce cytochrome P450 (CYP) 3A4 and P-glycoprotein through pregnane X-receptor activation. Our study evaluated the effects of long-term SJW administration on oral and intravenous pharmacokinetics of the nonmetabolized in vivo probe of P-glycoprotein, talinolol, in relation to intestinal P-glycoprotein expression. In a controlled, randomized study (N=9), the pharmacokinetics of oral (50 mg) and intravenous talinolol (30 mg) was determined before and after 12 days SJW (900 mg daily, Jarsin 300). Duodenal biopsies were taken and MDR1 genotypes assessed. SJW reduced the oral talinolol bioavailability by 25% (P=0.049) compared with water control. A 93% increase in oral clearance (P=0.177) and a 31% reduction in area under the serum concentration time curve (AUC; P=0.030) were observed. Renal and nonrenal clearance (CLNR), elimination half-life, peak serum drug concentration (Cmax), and time to reach Cmax were not significantly altered. After intravenous talinolol, SJW affected only CLNR (35% increase compared with water, P=0.006). SJW increased MDR1 messenger ribonucleic acid (mRNA) as well as P-glycoprotein levels in the duodenal mucosa. Subjects with the combined MDR1 genotype comprising 1236C>T, 2677G>T/A, and 3435C>T polymorphisms had lower intestinal MDR1 mRNA levels and displayed an attenuated inductive response to SJW as assessed by talinolol disposition. Long-term SJW decreased talinolol AUC with a corresponding increase in intestinal MDR1 expression, suggesting that SJW has a major inductive effect on intestinal P-glycoprotein. Interestingly, the magnitude of induction appeared to be affected by MDR1 genotype.

Prednisolone concentration in the cochlea of patients with perilymph fistula

After iv administration of 200 mg prednisolone in patients with perilymph fistula, concentrations of the drug in the cochlea were determined. A specially adapted LC method was used for analysis. Mean concentrations of prednisolone in the perilymphe reached 95 ng/ml after 15-25 min, and 338 ng/ml after 30-45 min. The values reached 8 and 41% of the corresponding serum concentrations, respectively.

Simultaneous determination of bupivacaine, mepivacain, prilocaine and ropivacain in human serum by liquid chromatography–tandem mass spectrometry

A liquid chromatography-tandem mass spectrometric (LC-MS-MS) method with a rapid and simple sample preparation was developed and validated for the simultaneous determination of the local anesthetics bupivacaine, mepivacaine, prilocaine and ropivacaine in human serum. An external calibration was used. The mass spectrometer was operated in the multiple reaction monitoring mode. A good quadratic response over the range of 1.0-200.0 ng/ml was demonstrated. The accuracy for bupivacaine ranged from 93.2 to 105.7%, for mepivacaine from 96.2 to 104.3%, for prilocaine from 94.6 to 105.7% and for ropivacaine from 94.3 to 104.0%, respectively. The limit of quantification was 1.0 ng/ml for all substances. This method is suitable for pharmacokinetic studies.

A non-fatal oleander poisoning

The study presents a case of non-fatal poisoning with oleander blooms in a 47-year-old female, with emphasis on the importance of toxicological service in a clinical emergency. After repeated vomiting at home, the patient was admitted at the hospital with cardiac symptoms more than 18 h after the ingestion. Serum samples were assayed immunochemically for digitoxin-related compounds by electrochemiluminescent immunoassay, and using HPLC/MS/MS analysis for oleandrin, the main cardiac glycoside of Nerium oleander. Confirming the non-specific immunoassay results, which are often clinically over-interpreted, oleandrin was detected by HPLC/MS/MS in the serum sample in a concentration of 1.6 ng/ml upon admission. Comparison with previous reports indicates that single compound analysis only permits a toxicological assessment for oleander poisoning and results in the proposal to classify an oleandrin level between 1.0 and 2.0 ng/ml as toxic blood plasma/serum concentration.

Hydrophilic interaction chromatography combined with tandem-mass spectrometry to determine six aminoglycosides in serum

A specific and automated method was developed to quantitate the aminoglycosides amikacin, gentamicin, kanamycin, neomycin, paromomycin, and tobramycin simultaneously in human serum. Samples were prepared with an automated solid phase extraction (SPE). The hydrophilic interaction chromatography (HILIC) was used for separation of analytes from endogenous compounds and baseline separation. The aminoglycosides were detected with electrospray ionisation tandem mass spectrometry (ESI-MS-MS). Using a volume of 500 microl biological sample the lower limits of quantification were 100 ng/ml or better. The described HILIC-MS-MS method is suitable for therapeutic drug monitoring and for clinical and pharmcokinetical investigations of the aminoglycosides.

Determination of Tirofiban in human serum by liquid chromatography–tandem mass spectrometry

A liquid chromatography-tandem mass spectrometric (LC-MS-MS) method with a rapid and simple sample preparation was developed and validated for the determination of Tirofiban in biological fluids. Tirofiban in serum samples was extracted and cleaned up by using an automated solid phase extraction method. An external calibration was used. The mass spectrometer was operated in the multiple reaction monitoring mode (MRM). A good linear response over the range of 2-200ng/ml was demonstrated. The accuracy for Tirofiban ranged from 94.8 to 110.8% within-day and from 103.0 to 104.7% between-day. The lower limit of quantification was 2ng/ml. This method is suitable for pharmacokinetic studies.

Determination of neomycin by LC–tandem mass spectrometry using hydrophilic interaction chromatography

A specific, and automated method was developed to quantitate neomycin in human serum. Samples were prepared with an automated solid phase extraction (SPE). The hydrophilic interaction chromatography (HILIC) was used for additional sample cleanup and baseline separation. The analyte neomycin was detected with electrospray ionisation tandem mass spectrometry (ESI-MS-MS). Using a volume of 500 microl biological sample the lower limit of quantification was 100 ng/ml. The described HILIC-MS-MS method is suitable for clinical and pharmcokinetical investigations of neomycin.

Increasing sample throughput in pharmacological studies by using dual-column liquid chromatography with tandem mass spectrometry

A robust novel technology of parallel chromatography combined with tandem mass spectrometry was successfully applied to a biological matrix extract for analyte detection. The presented study shows how only by using an additional isocratic pump, a second column and a 10-port valve the throughput is twice of that of a conventional single column system with the same sensitivity. Analytes and matrix were separated and eluting peaks of the first column were detected while the second column was equilibrated. The system was tested and used for the determination of several drugs, metabolites and endogenous compounds (i.e., propiverine, talinolol, scopolamine and leukotrienes).

Pharmacokinetics of oral talinolol following a single dose and during steady state in patients with chronic renal failure and healthy volunteers

OBJECTIVE

The objective of this study was to investigate the effect of renal impairment on the pharmacokinetics of the selective beta1-receptor antagonist talinolol.

METHODS

Pharmacokinetic data were obtained in 12 healthy volunteers, 12 patients with renal impairment and 8 patients with terminal renal insufficiency after the oral administration of 100 mg talinolol and under steady state conditions (100 mg talinolol daily). Concentrations of talinolol in plasma, urine and dialysate during hemodialysis were measured with a validated HPLC-method.

RESULTS

Talinolol is absorbed quite rapidly from the gastrointestinal tract (tmax 2.5-4 h). Steady state conditions were reached within 3-4 days depending on renal function. The calculated mean elimination half-life (t(1/2z)) in healthy volunteers (11 male, 1 female) was about 12 h. After an oral dose of 100 mg, about 55% of the bioavailable talinolol is eliminated unchanged in the urine. This fraction is reduced to 25% in patients with moderate to severe renal failure. A strong correlation was found between the renal elimination of talinolol and creatinine clearance. In patients with renal failure, the delayed elimination leads to an increase in t(1/2z) and to a decrease in the apparent total body clearance. Steady state trough levels (c(min)ss) in these patients are about 2.2-fold higher than in volunteers. The hemodialysability of talinolol was low.

CONCLUSION

The disposition of talinolol shows a strong dependence on the renal function. On the basis of the kinetic data for talinolol, dose reductions of 30-50% are recommended in subjects with moderate to severe renal impairment.

Determination of scopolamine in human serum and microdialysis samples by liquid chromatography-tandem mass spectrometry

A liquid chromatographic-tandem mass spectrometric (LC-MS-MS) method with a rapid and simple sample preparation was developed for the determination of scopolamine in biological fluids. Scopolamine and the internal standard atropine in serum samples were extracted and cleaned up by using an automated solid phase extraction method. Microdialysis samples were directly injected into the LC-MS system. The mass spectrometer was operated in the multi reaction monitoring mode. A good linear response over the range of 20 pg/ml to 5 ng/ml was demonstrated. The accuracy for added scopolamine ranged from 95.0 to 104.0%. The lower limit of quantification was 20 pg/ml. This method is suitable for pharmacokinetic studies.

Pharmacokinetic-pharmacodynamic modeling of the electroencephalogram effects of scopolamine in healthy volunteers

Scopolamine is a muscarinic receptor antagonist commonly used as a pharmacological model substance based on the "cholinergic hypothesis" of memory loss in senile dementia of the Alzheimer type. The objective of the study was to relate pharmacodynamic electroencephalogram (EEG) changes and scopolamine serum concentration using pharmacokinetic-pharmacodynamic (PK-PD) modeling techniques. This was a randomized, three-way crossover, open-label study involving 10 healthy nonsmoking young male volunteers who received either scopolamine 0.5 mg as an intravenous (i.v.) infusion over 15 minutes or an intramuscular (i.m.) injection or a placebo. The pharmacodynamic EEG measure consists of the total power in delta, theta, alpha, and beta bands over frontal, central, and occipital brain areas. The values of the pharmacokinetic parameters of scopolamine after i.v. infusion were clearance (CL) 205 +/- 36.6 L/h, volume of distribution (Vd) 363 +/- 66.7 L, distribution half-life (t1/2 alpha) 2.9 +/- 0.67 min, and terminal half-life (t1/2 beta) 105.4 +/- 9.94 min (mean +/- SEM). Mean peak serum concentrations (Cmax) were 4.66 and 0.96 ng/ml after i.v. and i.m. administration, respectively (p < 0.05). The area under the serum concentration versus time curve (AUC) after i.m. administration (81.27 +/- 11.21 ng/ml/min) was significantly lower compared to the value after i.v. infusion (157.28 +/- 30.86 ng/ml/min) (mean +/- SEM, p < 0.05). Absolute bioavailability of scopolamine after i.m. injection was 57% +/- 0.08% (mean +/- SEM). After both i.v. and i.m. administration, scopolamine induced a decrease in EEG alpha power (7.50-11.25 Hz) over frontal, central, and occipital brain areas compared to placebo (p < 0.05). The individual concentration-EEG effect relationships determined after i.v. infusion of scopolamine were successfully characterized by a sigmoidal Emax model. The averaged values of the pharmacodynamic parameters were E0 = 0.58 microV2, Emax = 0.29 microV2, EC50 = 0.60 ng/ml, and gamma = 1.17. No time delay between serum concentrations and changes in alpha power was observed, indicating a rapid equilibration between serum and effect site. The results provide the first demonstration of a direct correlation between serum concentrations of scopolamine and changes in total power in alpha frequency band in healthy volunteers using PK-PD modeling techniques. As regards the effect on the EEG, 0.5 mg of scopolamine administered i.v. appears to be a suitable dose.

Influence of grapefruit juice on scopolamine pharmacokinetics and pharmacodynamics in healthy male and female subjects

OBJECTIVES

To investigate the effects of grapefruit juice on absolute bioavailability of scopolamine in healthy subjects and to evaluate differences in pharmacokinetics and pharmacodynamics between genders.

SUBJECTS, MATERIAL AND METHODS

14 healthy subjects (7 men and 7 women) received scopolamine 0.5 mg as intravenous infusion, and as oral ingestion with and without grapefruit juice on separate occasions. Serum and urine samples were analyzed using gas chromatography-ion trap tandem mass spectrometry. Changes in subjective state were determined up to 24 hours after drug administration.

RESULTS

After oral administration, pretreatment with grapefruit juice led to a 30% increase in systemic bioavailability of scopolamine (p = 0.005) and a significant increase in time to reach peak serum concentration (tmax) of scopolamine (p < 0.001). The Cmax value (6.61+/-0.63 ng/ml) of scopolamine after i.v. administration in male subjects was significant higher compared with the value in female subjects (3.93+/-0.04 ng/ml; geometric mean +/- SEM; p = 0.007). No differences were found in urinary excretion rate of scopolamine and scopolamine glucuronide across genders and between the three different routes of scopolamine administration. Scopolamine produced time-dependent decrements in subjective alertness while contentment and calmness were not influenced.

CONCLUSIONS

Pretreatment with grapefruit juice delayed the absorption and increased the bioavailability of scopolamine, whereas elimination was not significantly affected. This study identified an influence of gender on Cmax of scopolamine after i.v. infusion.

Induction of P-glycoprotein by rifampin increases intestinal secretion of talinolol in human beings: a new type of drug/drug interaction

BACKGROUND

P-Glycoprotein is an efflux pump in many epithelial cells with excretory function. It has been demonstrated that rifampin (INN, rifampicin) induces P-glycoprotein, particularly in the gut wall. We therefore hypothesized that rifampin affects pharmacokinetics of the P-glycoprotein substrate talinolol, a beta1-blocker without appreciable metabolic disposition but intense intestinal secretion in human beings.

METHODS

Pharmacokinetics of talinolol (a single dose of 30 mg administered intravenously or 100 mg administered orally for 7 days) and duodenal expression of the MDR1 gene product P-glycoprotein as assessed by reverse transcriptase-polymerase chain reaction of the MDR1-messenger ribonucleic acid, by immunohistochemistry and Western blot analysis were analyzed before and after coadministration of rifampin (600 mg per day for 9 days) in 8 male healthy volunteers (age 22 to 26 years).

RESULTS

During rifampin treatment, the areas under the curve of intravenous and oral talinolol were significantly lower (21% and 35%; P < .05). Treatment with rifampin resulted in a significantly increased expression of duodenal P-glycoprotein content 4.2-fold (2.9, 6.51) (Western blot) and messenger RNA was increased in six of the eight volunteers. P-Glycoprotein expression in biopsy specimens of gut mucosa correlated significantly with the systemic clearance of intravenous talinolol (rs = 0.74; P < .001).

CONCLUSIONS

Rifampin induces P-glycoprotein-mediated excretion of talinolol predominantly in the gut wall. Moreover, clearance of talinolol from the blood into the lumen of the gastrointestinal tract may be predicted by the individual intestinal P-glycoprotein expression. Thus we describe a new type of steady-state drug interaction affecting compounds that are subject to transport rather than metabolism.

Oral bioavailability of digoxin is enhanced by talinolol: evidence for involvement of intestinal P-glycoprotein

OBJECTIVE

Recent data indicated that disposition of oral digoxin is modulated by intestinal P-glycoprotein. The cardioselective beta-blocker talinolol has been described to be secreted by way of P-glycoprotein into the lumen of the gastrointestinal tract after oral and intravenous administration. We therefore hypothesized that coadministration of digoxin and talinolol may lead to a drug-drug interaction based on a competition for intestinal P-glycoprotein.

METHODS

Pharmacokinetics of digoxin (0.5 mg orally), talinolol (30 mg intravenously and 100 mg orally), and digoxin plus talinolol orally, as well as digoxin plus talinolol intravenously, were assessed in five male and five female healthy volunteers (age range, 23 to 30 years; body weight, 60 to 95 kg) in a changeover study with at least a 7-day washout period. Digoxin and talinolol were analyzed by fluorescence polarization immunoassay and HPLC, respectively.

RESULTS

Oral coadministration of 100 mg talinolol increased the area under the concentration-time curve (AUC) from 0 to 6 hours and the AUC from 0 to 72 hours of digoxin significantly by 18% and 23%, respectively (5.85+/-1.49 versus 7.22+/-1.29 ng x h/mL and 23.0+/-3.3 versus 27.1+/-3.7 ng x h/mL, for both P<.05) and the maximum serum levels by 45%. Renal clearance and half-life of digoxin remained unchanged. Coinfusion of 30 mg talinolol with oral digoxin had no significant effects on digoxin pharmacokinetics. Digoxin did not affect the disposition of talinolol after both oral and intravenous administration.

CONCLUSION

We observed a significantly increased bioavailability of digoxin with oral coadministration of talinolol, which is most likely caused by competition for intestinal P-glycoprotein.

Effects of rifampicin and cimetidine on pharmacokinetics and pharmacodynamics of lamotrigine in healthy subjects

OBJECTIVE

To study the effects of rifampicin, a potent inducer of the microsomal P450 enzyme system and of specific isoforms of the uridine 5'-diphosphate(UDP)-glucuronyl-transferase enzyme system, and cimetidine, a known inhibitor of the hepatic microsomal cytochrome P450 enzyme system, on pharmacokinetics and pharmacodynamics of lamotrigine in healthy subjects.

METHODS

Ten healthy male subjects received a single oral dose of 25 mg lamotrigine after a 5-day pretreatment with (1) cimetidine 800 mg divided into two equal doses, (2) rifampicin 600 mg, or (3) placebo. Serum and urine samples were analyzed using high-performance liquid chromatography. Changes in electroencephalographic (EEG) power were determined up to 48 h after lamotrigine administration.

RESULTS

The values of the pharmacokinetic parameters of lamotrigine were: clearance over bioavailability (CL/F) 2.60+/-0.40 l/h, renal clearance (CLR) 0.10+/-0.03 l/h, terminal half-life (t1/2) 23.8+/-2.1 h, mean peak serum concentration (Cmax) 0.29+/-0.02 microg/l, time to reach Cmax (tmax) 1.6+/-0.28 h, and total area under the serum concentration-time curve (AUC0-infinity) 703.99+/-82.31 microg/ ml/min (mean +/- SEM). The amount of lamotrigine excreted as glucuronide was 8.90+/-0.77 mg. Rifampicin significantly increased CL/F (5.13+/-1.05 l/h) and the amount of lamotrigine excreted as glucuronide (12.12+/-0.94 mg), whereas both t1/2 (14.1+/-1.7 h) and AUC(0-infinity) (396.24+/-60.18 microg/ml/min) were decreased (P<0.05). Cimetidine failed to affect pharmacokinetics of lamotrigine. Lamotrigine did not change EEG power.

CONCLUSION

Rifampicin altered pharmacokinetics of lamotrigine due to induction of the hepatic enzymes responsible for glucuronidation, while coadministration of cimetidine to ongoing lamotrigine therapy has negligible effects on lamotrigine pharmacokinetics. Lamotrigine administered as a single dose of 25 mg has no effect on EEG power in healthy subjects.

Physostigmine reversal of midazolam-induced electroencephalographic changes in healthy subjects

OBJECTIVE

Midazolam is a water-soluble benzodiazepine. Flumazenil is a potent antagonist of midazolam-induced sedation. Physostigmine has also been shown to reverse benzodiazepine sedation in anecdotal reports. The aim of this study was to quantitatively characterize the reversal of midazolam-induced changes in electroencephalogram (EEG) by physostigmine compared to flumazenil and placebo.

METHODS

Twelve healthy male subjects received 5 mg midazolam as an intravenous infusion over 15 minutes. Fifteen minutes after the end of infusion, single doses of either 0.4 mg flumazenil, 0.5 mg physostigmine, or placebo (physiologic saline solution) were administered as intravenous injections in a randomized crossover fashion. Midazolam serum concentrations were measured using liquid chromatography-tandem mass spectrometry. The time from the start of injection until awakening was noted and the EEG was measured.

RESULTS

Four subjects were excluded from further pharmacokinetic and pharmacodynamic analysis because no midazolam-induced changes on EEG alpha power could be observed in each of the three study periods. The pharmacokinetics of midazolam were not influenced by flumazenil or physostigmine. Midazolam induced a decrease in EEG alpha power (7.50 to 11.25 Hz) compared with baseline (P < .05). After injection of flumazenil and physostigmine, an increase in EEG alpha power was observed, whereas placebo did not affect alpha power. Subjects opened their eyes 25.2 +/- 1.1 minutes after the placebo injection was begun, whereas subjects awoke after 6.2 +/- 2.7 minutes and 15.4 +/- 3.4 minutes after they received flumazenil and physostigmine, respectively (mean +/- SEM; P < .001).

CONCLUSION

Physostigmine and flumazenil antagonized midazolam-induced sedation. This suggests that a reversible central anticholinergic mechanism may be involved in the sedative action of midazolam.

P-glycoprotein inhibitor erythromycin increases oral bioavailability of talinolol in humans

OBJECTIVE

Increased bioavailability of the P-glycoprotein (Pgp) substrates digoxin and cyclosporin due to erythromycin has been observed in vivo. The aim of the present study was to investigate the effect of orally administered erythromycin on the oral bioavailability of the beta-blocker talinolol. Talinolol is a suitable model compound for Pgp drug-drug interaction studies due to its Pgp-related active intestinal secretion and lack of any significant metabolism.

METHODS

In a randomized crossover study, the oral pharmacokinetics of talinolol (50 mg) after a concomitant single oral dose of erythromycin (2 g) or placebo were investigated in 9 healthy men. Concentrations of talinolol were measured in serum and urine by HPLC.

RESULTS

The area under the curve of talinolol serum concentrations from 0 to 24 h (AUC(0-24)) and the maximum serum concentrations (Cmax) were significantly increased after administration of erythromycin compared to placebo. t(max) values were significantly reduced. The renal clearance (CLR) of talinolol was unchanged after co-administration of erythromycin and there was a small but statistically significant decrease in elimination half-life (t1/2). Serum pharmacokinetics correlate with the results derived from urine concentration measurement. One subject suffered from moderate diarrhea after erythromycin and was excluded from the analysis.

CONCLUSION

We suggest that the increase in oral bioavailability of talinolol after concomitant erythromycin is caused by increased intestinal net absorption due to Pgp inhibition by erythromycin.

The effect of age on pharmacokinetics of the local anesthetic drug articaine

BACKGROUND AND OBJECTIVES

With increasing age, there are physiologic changes that could affect pharmacokinetics of drugs. More elderly patients are undergoing routine dental procedures for which local anesthesia could be required. The goal of the present study was to evaluate the effect of age on pharmacokinetics of the local anesthetic agent articaine.

METHODS

The submucosal infiltration anesthesia from two different dosages of 4% articaine without epinephrine was compared in healthy elderly and young volunteers. High performance liquid chromatography has been used to determine concentrations of articaine in serum. Basic pharmacokinetic parameters were calculated according to standard procedures using a two-exponent equation.

RESULTS

The clearance and volume of distribution (Vdss) of articaine after infiltration anesthesia were significantly lower in elderly volunteers compared with young volunteers. The area under the serum concentration-time curve and maximum drug concentration (Cmax) values did not differ significantly with age; however, both parameters tended to be higher in elderly volunteers. No changes in terminal half-life and time to reach maximum serum concentration (t(max)) were observed. The Cmax and tmax values of the metabolite articainic acid were similar in young and elderly volunteers. CONCLUSIONS The results show that the metabolism of articaine is age-independent in healthy male volunteers. The smaller Vdss in the elderly results in a trend to higher serum levels after a given dose of articaine. No change of dosage of articaine in elderly patients should be necessary.

Intestinal secretion of intravenous talinolol is inhibited by luminal R-verapamil

OBJECTIVE

To examine the secretion of the beta1-adrenergic receptor antagonist talinolol into the small intestine during its intravenous administration and to show the relevance of the P-glycoprotein-modulating drug verapamil for this secretory transport mechanism in humans.

METHODS

In six healthy volunteers the intestinal steady-state perfusion technique (triple lumen tubing system) was used for measuring the appearance of talinolol within the small intestine while the drug was infused intravenously. During four of the seven perfusions performed, the perfusion fluid was changed from a verapamil-free solution and talinolol appearance was measured while a R-verapamil-containing solution (565 micromol/L) was perfused.

RESULTS

Talinolol was transported into the intestinal lumen up to a concentration gradient between lumen and blood of about 5.5:1. While perfusing the small intestine with a verapamil-free solution, the intestinal secretion rate of talinolol ranged from 1.94 to 6.62 microg/min per 30 cm length of the intestine (median values). Perfusion of a R-verapamil-containing perfusion fluid resulted in lower secretion rates (0.59 to 3.71 microg/30 cm x min), corresponding to 29% to 56% of the values obtained without verapamil supplied intraluminally.

CONCLUSION

Intravenously administered talinolol is actively secreted into the human small intestine. This secretion is reduced by the intraluminal supply of the P-glycoprotein modulating drug R-verapamil. This gives further rationale for P-glycoprotein-mediated intestinal drug secretion as a cause for incomplete oral bioavailability and for drug interactions during intestinal absorption.

Sensitive method for the determination of the antiarrhythmic drug detajmium in serum by solid-phase extraction and high-performance liquid chromatography with fluorimetric detection

The objective of this study was to develop a very sensitive and selective method for the determination of detajmium (4-3-diethylamino-2-hydroxypropyl-ajmaline), a sodium-channel-blocking drug with antiarrhythmic properties, in serum. A high-performance liquid chromatography (HPLC) method with solid-phase extraction and fluorimetric detection has been applied. Serum samples were diluted with phosphate buffer (pH 3.5) and the extraction of detajmium and ajmaline, which was used as an internal standard, was carried out with Oasis cartridges (Waters). The chromatographic separation was performed on a RP18 column. The limit of quantification for serum samples of detajmium was 1 ng/ml with good reproducibility (R.S.D. < 15%) and a linear response from 1 to 200 ng/ml. The described method is highly sensitive and specific for the determination of detajmium in serum of patients and volunteers.

Solid-phase extraction and high-performance liquid chromatographic determination of articainic and its metabolite articainic acid in human serum

A new method is described using solid-phase extraction (SPE) for preconcentration of articaine and the metabolite articainic acid and high-performance liquid chromatography (HPLC) for the determination of both compounds in human serum. Articaine and articainic acid were extracted in one step with SDB-RPS disk cartridges after precipitation of the serum proteins by perchloric acid. The HPLC separation was then performed on a reversed-phase C8 column using phosphate buffer-acetonitrile (88:12, v/v). UV absorption at 274 nm was used for measuring the analytes with a low limit of quantitation of about 10 ng/ml, which is appropriate for pharmacokinetic studies of low dose submucosal injections of the local anaesthetic agent articaine hydrochloride in dentistry.

Unexpected effect of verapamil on oral bioavailability of the beta-blocker talinolol in humans

PURPOSE

To quantitate the effect of verapamil administered orally, a calcium channel blocker and potent inhibitor of P-glycoprotein on oral pharmacokinetics of the beta1-adrenergic receptor antagonist talinolol, a substrate of P-glycoprotein.

SUBJECTS AND METHODS

In a randomized, crossover placebo-controlled study, oral pharmacokinetics of talinolol (50 mg) after concomitant administration of single doses of R-verapamil (120 mg) or placebo were investigated in 9 healthy volunteers. Concentrations of talinolol, verapamil, and its main metabolite norverapamil were measured in serum with HPLC. Concentrations of talinolol were also measured in urine by HPLC. Standard pharmacokinetic parameters were calculated with noncompartmental procedures.

RESULTS

The area under the concentration-time curve for talinolol from 0 to 24 hours was significantly decreased after R-verapamil versus placebo (721+/-231 ng x h x mL(-1) versus 945+/-188 ng x h x mL(-1); P < .01). Maximum serum concentration of talinolol was reached significantly earlier after R-verapamil compared with placebo (P < .05). Coadministration of R-verapamil did not affect the renal clearance or half-life of talinolol. Serum pharmacokinetics are paralleled by the results derived from urine concentrations of talinolol.

CONCLUSION

This is the first study to show a decreased oral bioavailability of a P-glycoprotein substrate (talinolol) in humans as a result of coadministration of verapamil. This effect is assumed to be caused by changes of the intestinal net absorption of talinolol because its renal clearance remains unaffected by administration of R-verapamil. This unexpected effect of R-verapamil is most likely dose dependent as a result of an interplay between intestinal P-glycoprotein and gut metabolism.

Pharmacokinetics and pharmacodynamics of scopolamine after subcutaneous administration

The effects of subcutaneously administered scopolamine on quantitative electroencephalogram (qEEG) and cognitive performance were evaluated and correlated with pharmacokinetic parameters in a randomized, double-blind placebo-controlled crossover study of 10 healthy male volunteers. Changes in qEEG and cognition were determined for 8 hours after drug administration. Scopolamine produced dose- and time-dependent impairments of attention and memory and a time-dependent increase in delta power (1.25-4.50 Hz) and a decrease in fast alpha power (9.75-12.50 Hz) on qEEG compared with placebo. Maximum serum concentrations of scopolamine occurred 10 to 30 minutes after drug administration. Mean peak serum concentrations (free base) were 3.27, 8.99, and 18.81 ng/mL after administration of 0.4, 0.6 mg, and 0.8 mg scopolamine, respectively. Elimination half-life was approximately 220 minutes. The findings indicate temporary changes in qEEG and psychometric tests, and support the possible use of such a testing model for impaired cognitive functions such as age-related memory disturbances.

Determination of drugs in biological fluids by high-performance liquid chromatography with on-line sample processing

An automated two column HPLC system with the new packing material LiChrospher RP-18 ADS (alkyl-diol-silica) was tested for the determination of several drugs and metabolites (talinolol, celiprolol, metoprolol, oxprenolol, triamterene, trimethoprim, tiracizine, articaine, detajmium, ajmaline, lamotrigine) in various biological fluids (serum, urine, intestinal aspirates, supernatants of cell cultures and supernatants after protein denaturation). The method allows the direct injection of biological fluids into a reversed-phase HPLC system and on-line clean-up and sample enrichment by a column-switching technique. Precision, accuracy and sensitivity were similar to conventional assays as described in the literature. With this new method it was possible to measure drug concentrations in various biological fluids without changing the sample preparation procedure. In some cases an additional sample preparation like protein denaturation or solid-phase extraction was advantageous to enhance the sensitivity of the method and the life-time of the ADS column.

Clinical pharmacokinetics of articaine

Articaine is the most widely used local anaesthetic agent in dentistry in a number of European countries. The amide structure of articaine is similar to that of other local anaesthetics, but it contains an additional ester group which is quickly hydrolysed by esterases. High performance liquid chromatography has been used to determine the concentrations of articaine and its metabolite articainic acid in serum. Rapid sample preparation is critical in the accurate determination of articaine serum concentrations, since blood and serum are the sites of metabolism. The time to maximum drug concentrations of articaine occurs about 10 to 15 minutes after submucosal injection of articaine 4% 80 mg, irrespective of epinephrine (adrenaline). The mean maximum plasma drug concentration is about 400 micrograms/L for articaine with epinephrine 1:200,000 and 580 micrograms/L for articaine without epinephrine. The elimination half-time of articaine is about 20 minutes. The rapid breakdown of articaine to the inactive metabolite articainic acid is related to a very low systemic toxicity and consequently to the possibility of repeated injections. Equal analgesic efficacy along with lower systemic toxicity (i.e. a wide therapeutic range) permits the use of articaine in higher concentrations than other amide-type local anaesthetics. Complete anaesthesia can be observed in nearly 90% of all cases, using articaine 4% 60 to 80 mg with epinephrine 1:200,000. Articaine is better able to diffuse through soft tissue and bone than other local anaesthetics. The concentration of articaine in the alveolus of a tooth in the upper jaw after extraction was about 100 times higher than that in systemic circulation. The plasma protein binding rate of articaine and articainic acid is 70%. It has been concluded that an unintentional intravascular injection of articaine 80 mg does not cause toxic effects in healthy individuals.

"Reduction" of CGG trinucleotide expansion from mother to offspring in seven fragile-X families

Apparent reduction in the size of the CGG repeat is reported from seven fragile-X mothers to nine offspring in seven extended families. The overall frequency of the reduction amongst 121 fragile-X mother-fragile-X child transmissions was 7.4%, compared with an 18% reduction in fragile-X father-fragile-X daughter transmissions, but ascertainment bias may account for some underestimation of the frequency of reductions, especially between mothers and their offspring. In one mother-son transmission, a premutation present in the son (with a full mutation present in the mother) was unmethylated. This may be the result of either demethylation with reduction, or undetected mosaicism in the mother. There was no obvious increase in the level of intellectual performance in female offspring who received a reduced fragment from their mothers. Several mechanisms leading to apparent reduction, such as germline mosaicism, deletion or replication slippage, should be considered.

Saturable in vitro metabolism of articaine by serum esterases. Does it contribute to the persistence of the local anesthetic effect?

BACKGROUND AND OBJECTIVES

The amide-type local anesthetic articaine is unique in that hydrolysis to articainic acid by serum esterases is its main metabolic pathway. The purpose of the present investigation was to study the concentration dependence of this pathway in vitro.

METHODS

To unbuffered (pH 8.2) as well as phosphate-buffered (pH 7.4) heated serum samples were added various amounts of articaine in the range 10-300 micrograms/mL. Concentrations of articaine and articainic acid were measured by high-performance liquid chromatography after incubating the samples at 37 degrees C for intervals ranging from 5 minutes to 6 hours after addition of articaine.

RESULTS

The in vitro metabolism of articaine was shown to undergo pH-dependent Michaelis-Menten kinetics, indicating saturation at higher substrate concentrations. The Michaelis constant K(m) was determined as 175 micrograms/mL and 22.1 micrograms/mL and the maximum reaction rate Vmax as 2.1 micrograms/mL/min and 0.17 microgram/mL/min at pH 8.2 and pH 7.2, respectively. These results support previous in vivo observations that suggest saturable articaine metabolism, indicated by higher articaine/articainic acid metabolic ratio with higher articaine concentrations in alveolar blood after dental extraction.

CONCLUSION

Local saturation of the serum esterases may contribute to the advantageous relationship between persistence of the local anesthetic effect and low systemic toxicity caused by the last systemic elimination of articaine (ie, its wide toxic therapeutic ratio).

Determination of scopolamine in human serum by gas chromatography-ion trap tandem mass spectrometry

The objective of this study was to develop a very sensitive and selective method for the determination of scopolamine in serum with a rapid and simple sample preparation. A capillary column gas chromatographic-ion trap tandem mass spectrometric technique has been applied. Scopolamine and the internal standard mexiletine were extracted from serum samples and cleaned up by using a single step liquid-liquid extraction. Derivatization was carried out using 2,2,2-trifluoro-N-methyl-N-trimethylsilylacetamide. The mass spectrometer was operated with positive ions in the selected reaction mode with chemical ionisation using methane. The sum of peak height of two daughter ions was used for quantification. The detection limit was 50 pg/ml in serum.

Direct demonstration of small intestinal secretion and site-dependent absorption of the beta-blocker talinolol in humans

OBJECTIVE

To examine the relevance of site-dependent small intestinal absorption for incomplete intestinal absorption of the poorly metabolized beta 1-adrenergic receptor antagonist talinolol.

METHODS

The intestinal steady-state perfusion technique (triple lumen tubing system with a 30 cm test segment) for intraluminal measurements was combined with simultaneous determination of talinolol serum concentrations. Dissolved talinolol was perfused over 160 minutes into different parts of the small intestine. The middle of the test segment was located between 25 and 235 cm beyond the teeth. Each of the six healthy subjects was studied twice with a proximal and a more distal site of perfusion to allow for comparisons within an individual subject.

RESULTS

The area under the curve for serum concentrations from 0 to 480 minutes [AUC(0-480 min)] and the maximum serum concentration after distal perfusions corresponded to only 15% to 73% and 7% to 90% of the proximal values, respectively. AUC decreased with increasing distance from the teeth. The mean amount of talinolol absorbed from the test segment per unit time (intestinal transport rate) corresponds to only one-tenth of the amount of drug offered to the test segment (perfusion rate). There was a direct correlation between the perfusion rate of talinolol and its transport rate for both regions and in all subjects investigated. However, to achieve the same transport rate in the distal region a higher perfusion rate is required, compared to the proximal small intestine. At perfusion rates lower than 600 micrograms/min, net secretion of talinolol into the intestinal lumen occurred against a steep concentration gradient blood: lumen of about 1:4200.

CONCLUSION

Talinolol oral bioavailability of 55% is due to a low absorption rate and a decrease of absorption capabilities along the small intestine. Net absorption of talinolol is reduced by the involvement of active intestinal secretion.

New sensitive method for the determination of hydrochlorothiazide in human serum by high-performance liquid chromatography with electrochemical detection

A HPLC method with a very sensitive electrochemical detection has been developed for determining the diuretic agent hydrochlorothiazide (HCT) in serum of volunteers to whom a single dose of the fixed combination of 12.5 mg HCT and 25 mg triamterene was administered. In the present method samples (0.2 ml serum, pH 7) were purified by extraction of HCT into 5 ml tert.-butyl-methyl ether. The separated organic phase was spiked with p-aminobenzoic acid (PABA) standard. The separation was performed on a reversed-phase C18 column using phosphate buffer-acetonitrile (90:10). A coulometric cell was used to measure HCT and an ultraviolet detector for PABA. The limit of quantitation for serum samples of only 200 microliters was 5 ng/ml (i.e. 60 pg HCT/injection) with a good reproducibility (1-8%). Short retention times were found: 1.2 min for PABA and 5.8 min for HCT.

Pharmacokinetics of the antiarrhythmic agent tiracizine: steady state kinetics in comparison with single-dose kinetics

Serum and urine kinetics of unchanged tiracizine (T), a new class I antiarrhythmic agent, and three metabolites (M1, 2, and 3) were assessed in eight healthy extensive metabolizers after a single oral administration of 50 mg tiracizine and during steady state (50 mg b.i.d.). Additionally, tiracizine-induced ECG changes were measured. Considerable accumulation of M1 and M2 was observed during repeated dosing (M1, Cmax,ss = 391.8 ng mL-1 against Cmax,sd = 132.8 ng mL-1; M2, Cmax,ss = 143.2 ng mL-1 against Cmax,sd = 25.8 ng mL-1). However, significant increases of AUC (AUC tau = 261.9 ng h mL-1 against AUC0-infinity,sd = 182.9 ng h mL-1), Cmax (Cmax,ss = 75.9 ng mL-1 against Cmax,sd = 56.9 ng mL-1) and t 1/2 beta (t 1/2 beta,ss = 4.0 h against t 1/2 beta,sd = 2.4 h) of the parent compound indicate non-linear kinetics. The significant decrease in renal clearance of all four substances as well as the decrease of non-renal tiracizine clearance with repeated dosing led to the assumption that non-linearity is due to saturable renal excretion and a fall in intrinsic tiracizine clearance. PQ time was prolonged significantly during steady state and culminated at the tmax of the parent compound, whereas there was no change in any ECG parameter after a single-dose administration of 50 mg tiracizine.