Comparison of five methodologies to apportion organic aerosol sources during a PM pollution event.

This study presents a comparison of five methodologies to apportion primary (POA) and secondary organic aerosol (SOA) sources from measurements performed in the Paris region (France) during a highly processed PM pollution event. POA fractions, estimated from EC-tracer method and positive matrix factorization (PMF) analyses, conducted on measurements from PM10 filters, aerosol chemical speciation monitor (ACSM) and offline aerosol mass spectrometry (AMS), were all comparable (2.2-3.7 µg m-3 as primary organic carbon (POC)). Associated relative uncertainties (measurement + model) on POC estimations ranged from 8 to 50%. The best apportionment of primary traffic OA was achieved using key markers (EC and 1-nitropyrene) in the chemical speciation-based PMF showing more pronounced rush-hour peaks and greater correlation with NOx than other traffic related POC factors. All biomass burning-related factors were in good agreement, with a typical diel profile and a night-time increase linked to residential heating. If PMF applied to ACSM data showed good agreement with other PMF outputs corrected from dust-related factors (coarse PM), discrepancies were observed between individual POA factors (traffic, biomass burning) and directly comparable SOA factors and highly oxidized OA. Similar secondary organic carbon (SOC) concentrations (3.3 ± 0.1 µg m-3) were obtained from all approaches, except the SOA-tracer method (1.8 µg m-3). Associated uncertainties ranged from 14 to 52% with larger uncertainties obtained for PMF-chemical data, EC- and SOA-tracer methods. This latter significantly underestimated total SOA loadings, even including biomass burning SOA, due to missing SOA classes and precursors. None of the approaches was able to identify the formation mechanisms and/or precursors responsible for the highly oxidized SOA fraction associated with nitrate- and/or sulfate-rich aerosols (35% of OA). We recommend the use of a combination of different methodologies to apportion the POC/SOC concentrations/contributions to get the highest level of confidence in the estimates obtained.

Speciation of organic fractions does matter for aerosol source apportionment. Part 3: Combining off-line and on-line measurements.

The present study proposes an advanced methodology to refine the source apportionment of organic aerosol (OA). This methodology is based on the combination of offline and online datasets in a single Positive Matrix Factorization (PMF) analysis using the multilinear engine (ME-2) algorithm and a customized time synchronization procedure. It has been applied to data from measurements conducted in the Paris region (France) during a PM pollution event in March 2015. Measurements included OA ACSM (Aerosol Chemical Speciation Monitor) mass spectra and specific primary and secondary organic molecular markers from PM10 filters on their original time resolution (30 min for ACSM and 4 h for PM10 filters). Comparison with the conventional PMF analysis of the ACSM OA dataset (PMF-ACSM) showed very good agreement for the discrimination between primary and secondary OA fractions with about 75% of the OA mass of secondary origin. Furthermore, the use of the combined datasets allowed the deconvolution of 3 primary OA (POA) factors and 7 secondary OA (SOA) factors. A clear identification of the source/origin of 54% of the total SOA mass could be achieved thanks to specific molecular markers. Specifically, 28% of that fraction was linked to combustion sources (biomass burning and traffic emissions). A clear identification of primary traffic OA was also obtained using the PMF-combined analysis while PMF-ACSM only gave a proxy for this OA source in the form of total hydrocarbon-like OA (HOA) mass concentrations. In addition, the primary biomass burning-related OA source was explained by two OA factors, BBOA and OPOA-like BBOA. This new approach has showed undeniable advantages over the conventional approaches by providing valuable insights into the processes involved in SOA formation and their sources. However, the origins of highly oxidized SOA could not be fully identified due to the lack of specific molecular markers for such aged SOA.

Speciation of organic fractions does matter for aerosol source apportionment. Part 2: Intensive short-term campaign in the Paris area (France).

The present study aimed at performing PM10 source apportionment, using positive matrix factorization (PMF), based on filter samples collected every 4h at a sub-urban station in the Paris region (France) during a PM pollution event in March 2015 (PM10>50µgm-3 for several consecutive days). The PMF model allowed to deconvolve 11 source factors. The use of specific primary and secondary organic molecular markers favoured the determination of common sources such as biomass burning and primary traffic emissions, as well as 2 specific biogenic SOA (marine+isoprene) and 3 anthropogenic SOA (nitro-PAHs+oxy-PAHs+phenolic compounds oxidation) factors. This study is probably the first one to report the use of methylnitrocatechol isomers as well as 1-nitropyrene to apportion secondary OA linked to biomass burning emissions and primary traffic emissions, respectively. Secondary organic carbon (SOC) fractions were found to account for 47% of the total OC. The use of organic molecular markers allowed the identification of 41% of the total SOC composed of anthropogenic SOA (namely, oxy-PAHs, nitro-PAHs and phenolic compounds oxidation, representing 15%, 9%, 11% of the total OC, respectively) and biogenic SOA (marine+isoprene) (6% in total). Results obtained also showed that 35% of the total SOC originated from anthropogenic sources and especially PAH SOA (oxy-PAHs+nitro-PAHs), accounting for 24% of the total SOC, highlighting its significant contribution in urban influenced environments. Anthropogenic SOA related to nitro-PAHs and phenolic compounds exhibited a clear diurnal pattern with high concentrations during the night indicating the prominent role of night-time chemistry but with different chemical processes involved.

Observational study in severe asthmatic patients after discontinuation of omalizumab for good asthma control.

INTRODUCTION: Severe persistent asthma represents a major and costly public health issue. There is evidence that long-term treatment with omalizumab might have disease-modifying activity but data on the consequences of discontinuing treatment after a positive response are limited. The purpose of this study was to investigate-in real-life prescribing conditions-what happens when omalizumab is discontinued in patients with severe, persistent allergic asthma who have responded well to omalizumab treatment. METHODS: An observational, descriptive, cross-sectional, retrospective study to establish the time to loss of asthma control after the discontinuation of courses of omalizumab treatment of varying duration. RESULTS: 24 lung specialists reviewed data from 61 responder patients who had discontinued omalizumab after a mean duration of 22.7 ± 13.1 [range: 2.5; 59.5] months of treatment. Loss of asthma control was documented in 34 patients (55.7%) with a median interval between discontinuation and loss of control of 13.0 months (mean 20.4 ± 2.6 [95% CI: 8.3-28.1]). No correlation was detected between time to loss of control and duration of treatment, although control tended to be sustained for longer in patients whose response had been classified as "excellent" as opposed to "good" (median: 17.0 vs. 12.8 months; NS). DISCUSSION: The discontinuation of omalizumab was not associated with any rebound effect or exacerbation of the disease, and control was sustained throughout the follow-up period of at least 6 months in nearly half of all patients, including all of those who had been treated for 3.5 years or more. After the reintroduction of omalizumab, 4 out of 20 patients did not respond again.

Omalizumab reduces oral corticosteroid use in patients with severe allergic asthma: real-life data.

BACKGROUND: Long-term oral corticosteroid (OCS) therapy is associated with significant burden on patients and healthcare resources; treatments that may help reduce their use are important to improve asthma management. METHODS: French and German clinicians prescribing omalizumab for >16 weeks to patients with severe persistent allergic asthma collected OCS use data. OCS use was recorded at baseline and at a non-specific time point beyond 16 weeks from initiation of omalizumab. The number of asthma exacerbations (FEV(1) < 60% of personal best, requiring OCS burst and unscheduled doctor/emergency visit or hospitalization) and asthma-related hospitalizations during the 12-months prior to omalizumab treatment and during the observation period were also recorded. RESULTS: Overall, 346 patients were treated with omalizumab for >16 weeks. Of these, 166 (48.0%) were receiving maintenance OCS (France, n = 64; Germany, n = 102). Following omalizumab therapy, 84 (50.6%) patients on OCS at baseline reduced/stopped OCS dose at the time of data collection; 34 (20.5%) stopped and 50 (30.1%) reduced OCS. In all patients receiving maintenance OCS at baseline, mean reduction from baseline in daily OCS dose was 29.6% (7.1 mg prednisolone). In patients who reduced/stopped maintenance OCS, mean reduction from baseline in daily OCS dose was 74.3% (15.4 mg prednisolone). Reductions in exacerbations and hospitalizations were observed from the 12-months prior to baseline in patients at the time of data collection, irrespective of change in OCS dose. CONCLUSION: European real-life experience demonstrates the OCS-sparing potential of omalizumab in some patients with severe allergic (IgE-mediated) asthma.

Omalizumab decreases nonspecific airway hyperresponsiveness in vitro.

BACKGROUND: In asthmatic patients, both symptoms and hyperresponsiveness are related to immunoglobulin E (IgE) concentration in serum. The anti-IgE monoclonal antibody omalizumab improved the control of asthma, but its effect on airway hyperresponsiveness is controversial. Passive sensitization reproduced in vitro a bronchial hyperresponsiveness, an increase in IgE bearing cells, and a mast cell degranulation. This study was designed to examine the effect of omalizumab on passive sensitization-induced hyperresponsiveness, alterations in IgE positive inflammatory cells and mast cell degranulation within the bronchial wall. METHODS: Proximal (3-5 mm diameter) and distal (0.5-1.5 mm diameter) human bronchi dissected out from 10 lung specimens were incubated in normal or asthmatic serum containing various concentrations of omalizumab. Contractile responses to histamine or Dermatophagoides pteronyssinus (D. pter) were recorded using an organ bath system and expressed as percentage of maximal contractile response to acetylcholine (ACh). Immunohistochemistry was performed using monoclonal antibodies directed against IgE or tryptase. Mast cells were classified as fully granulated (type I), partly (type II) or largely degranulated (type III). RESULTS: The specific bronchial hyperresponsiveness to D. pter and the nonspecific bronchial hyperresponsiveness to histamine following passive sensitization were significantly inhibited by omalizumab in both distal and proximal airways. Passive sensitization-induced increase in IgE positive cells was also abolished by omalizumab in a concentration dependent manner. Mast cell degranulation which was inhibited by omalizumab was positively correlated with the contractile response to D. pter. CONCLUSIONS: Omalizumab blocks specific and nonspecific bronchial hyperresponsiveness. Anti-IgE also decreases IgE bearing cell number and mast cell degranulation.

Comparison of electrochemiluminescence assay and ELISA for the detection of Clostridium botulinum type B neurotoxin.

We compared the ELISA and electrochemiluminescence (ECL) immunoassay technologies for the detection of botulinum type B neurotoxin (BotNT B), which requires highly sensitive techniques due to its potent biological activity. BotNT B complexes are the naturally secreted form of the toxin, approximately a third of which consists of the neurotoxin itself; they were aliquoted and frozen for this study. Results of both techniques were interpreted with the same standard statistical tests (ANOVA and Tukey). We first compared two commercial assays for BotNT B: the detection limit of the colorimetric ELISA was 1.56 ng/ml BotNT B complexes versus 0.39-0.78 ng/ml in the ECL test. We then used the same monoclonal antibody and the same polyclonal antibody, respectively purified by protein A and protein G chromatography, to optimize an in-house ELISA test and an in-house ECL test, making it possible to directly compare the two technologies without interference due to the properties of the antibodies used in the two tests. The colorimetric in-house ELISA had a detection threshold of 3.12 ng/ml versus the in-house ECL test whose detection threshold was 0.78-1.56 ng/ml. Thus, in both cases, the ECL assay was two to four times more sensitive than the colorimetric ELISA. The ECL assay was also more rapid (2.5 h for the in-house ECL versus 5 h for in-house ELISA with precoated wells). Overall, these elements can be used to compare the qualities of the two technologies, at least for the detection of protein antigens such as toxins.

FEV1 reversibility does not adequately predict effect of formoterol via Aerolizer in chronic obstructive pulmonary disease.

Evaluation of patients with chronic obstructive pulmonary disease (COPD) often includes the use of post-bronchodilator reversibility testing to guide treatment decisions. Recommendations for reversibility testing differ and there is no universally accepted method or outcome criterion. A survey of recent clinical trials with beta2-agonists in COPD illustrates the diversity of methods used to assess reversibility and highlights the difficulty of comparing data from such trials. Two recent studies demonstrated the benefits of treatment with the long-acting beta2-agonist bronchodilator formoterol (Foradil Aerolizer) in patients with COPD. When patients were classified according to their degree of reversibility as partially or poorly reversible, improvements were observed in both groups irrespective of the definition applied. These results suggest that bronchodilator reversibility testing should not be used as a rigid basis for treatment decisions with beta2-agonists in COPD patients. There is a pressing need for the role of reversibility testing to be clearly defined.

Continuing emissions of methyl chloroform from Europe.

The consumption of methyl chloroform (1,1,1-trichloroethane), an industrial solvent, has been banned by the 1987 Montreal Protocol because of its ozone-depleting potential. During the 1990s, global emissions have decreased substantially and, since 1999, near-zero emissions have been estimated for Europe and the United States. Here we present measurements of methyl chloroform that are inconsistent with the assumption of small emissions. Using a tracer transport model, we estimate that European emissions were greater than 20 Gg in 2000. Although these emissions are not significant for stratospheric ozone depletion, they have important implications for estimates of global tropospheric hydroxyl radical (OH) concentrations, deduced from measurements of methyl chloroform. Ongoing emissions therefore cast doubt upon recent reports of a strong and unexpected negative trend in OH during the 1990s and a previously calculated higher OH abundance in the Southern Hemisphere compared to the Northern Hemisphere.

Clinical efficacy with formoterol in the absence of a response to salmeterol: a review.

Salmeterol and formoterol are both beta 2-agonist bronchodilators with a long duration of action and are often classified together, yet they are distinctly different in their pharmacology. Recent evidence suggests there is a subpopulation of asthmatic patients who do not respond to salmeterol, yet can attain clinical benefit with formoterol. Following a literature search, three published case reports are reviewed as well as results from two published clinical trials designed specifically to document response to formoterol in 'non-responders to salmeterol' asthmatics. Possible mechanisms underlying this observation are discussed, including pharmacological differences of the two drugs relating to agonism at the beta 2-receptor and to effect on nuclear transcription factors.

Rapid onset of bronchodilation in COPD: a placebo-controlled study comparing formoterol (Foradil Aerolizer) with salbutamol (Ventodisk).

Formoterol fumarate is a beta2-agonist bronchodilator that combines a fast onset of action with a long duration of action. Its fast onset of action is well documented in asthma but has not been directly compared with that of salbutamol in patients with chronic obstructive pulmonary disease (COPD). This randomized, double-blind, placebo-controlled study was conducted to assess the bronchodilatory effects over the first 3 h after inhalation of single doses of formoterol 24 microg delivered via the Aerolizer dry powder inhaler device (double-blind), or salbutamol 400 microg delivered by a Diskhaler dry powder inhaler (single-blind) in patients with COPD. A total of 24 patients with COPD were randomized [mean age 61.6 +/- 7.8 years, mean forced expiratory volume in 1 sec (FEV1) 1.38 +/- 0.32 l and 45.8 +/- 9.6% of predicted]. Inhalation of formoterol or salbutamol resulted in similar increases in FEV from 0 to 3 h post-dose. Both drugs produced similar bronchodilation by 5 min, which became almost maximal by 30 min. The primary efficacy variable, the area under the curve (AUC) of the FEV increase above predose baseline from 0 to 30 min (AUC(0-30 min)), demonstrated significant effects for formoterol (mean 5.89 +/- 4.67 l min(-1)), and salbutamol (mean 6.06 +/- 4.34 l min(-1)), which were not statistically different from each other but statistically significantly higher (P<0.0001) than that observed with placebo (-0.32 +/- 2.59 l min(-1)). In addition, both formoterol and salbutamol produced similar and rapid increases in forced vital capacity (FVC). In summary, this study confirms the rapid onset of action of formoterol and indicates that the onset of action of formoterol and salbutamol are similar in patients with COPD.

Comparison between formoterol 12 microg b.i.d. and on-demand salbutamol in moderate persistent asthma.

Inhalation of on-demand salbutamol (ODS) several times daily is sometimes the only beta2-agonist prescribed in moderate persistent asthma, whereas a long-acting beta2-agonist should be added. This trial aimed to compare the efficacy of formoterol dry-powder capsule 12 microg b.i.d. (Foradil) and ODS in patients with moderate persistent asthma treated with inhaled corticosteroids, in the conditions of real practice. Two hundred and fifty-nine patients were randomized (formoterol; 130; ODS: 129) in this open, parallel-group trial. The mean increases in morning peak expiratory flow (PEF primary variable) and evening PEF over the 3-month treatment period were statistically significantly higher with formoterol: +25.7 and +24.1 l min(-1), respectively vs. +4.5 and +0.5 l min(-1) respectively with ODS. The increase in FEV1 was statistically significantly higher with formoterol at months 1 and 3. Formoterol reduced the use of salbutamol as rescue medication by two-thirds. The percentages of symptom-free days and nights statistically significantly increased with formoterol (+20% and +33% respectively), but did not significantly change with ODS. Clinically relevant and statistically significant improvement in the mean total score of the St George's Hospital Respiratory Questionnaire was observed in the formoterol group. Adverse events were similar in the two groups. The results show that treatment with formoterol has significant advantages over ODS in patients with moderate persistent asthma.

Use of formoterol dry powder administered for three months via a single-dose inhaler in 1,380 asthmatic patients.

Formoterol is a long-acting beta 2-adrenoceptor agonist available in a single-dose breath-actuated device (Foradil) for asthma treatment. Since efficacy and ease of use are key factors for compliance to therapy, the aim of this study was to assess correct use, efficacy and safety of Foradil in a 3-month, open, uncontrolled, multicenter trial. This study was performed on 1,380 patients with moderate or severe persistent asthma treated with inhaled corticosteroid (age: 48.4 +/- 16.2 years; FEV1: 65.4 +/- 19.4% of normal). During the study, compliance was over 90%. More than 90% of the patients used the inhaler correctly and found it easy or very easy to use. The mean increase in peak expiratory flow rate (PEFR), 30 to 60 min after inhalation, was 52.3 and 36.7 l/min for the morning and the evening respectively (p = 0.0001). This increase was already significant 5 min after inhalation, confirming the fast onset of action of formoterol. Mean predose PEFR and daytime/nocturnal symptom scores improved during the length of the study. Rescue short-acting beta 2-agonist consumption was more than three times reduced. At study completion, formoterol dosage was 12 micrograms and 24 micrograms twice daily for 71.5% and 28.5% of the patients respectively. Physicians judged the overall efficacy as good or very good in 87.1% of the patients, and they estimated the tolerability as very good or good in 92.6%. Drug-related adverse events were similar to those of other beta 2-agonists. In conclusion, this study demonstrated the ease of use of this formoterol single-dose dry powder inhaler, and confirmed the good efficacy and safety profile of this long-acting bronchodilator in asthma.

Long- and short-acting beta2 adrenoceptor agonists: interactions in human contracted bronchi.

The aim of this study was to systematically compare the interaction of the long-acting beta2-adrenoceptor agonists formoterol and salmeterol with short-acting beta2-adrenoceptor agonists in contracted human bronchi. Human bronchi were obtained at thoracotomy from patients with lung cancer. Formoterol or salmeterol at concentrations inducing up to 92 and 94% of their maximal relaxant effect, respectively, were added to bronchial rings contracted with carbachol (10(-6) M). After a time period of 30 min, concentration-response curves for the short-acting beta2-adrenoceptor agonists, salbutamol, terbutaline, isoprenaline and fenoterol were recorded. Administration of equieffective concentrations of salmeterol and formoterol, resulted in only salmeterol inducing a shift to the right of isoprenaline, terbutaline, fenoterol and salbutamol concentration-response curves. The rank order of shift was salbutamol > fenoterol > terbutaline > isoprenaline. Formoterol, up to concentrations of 3x10(-9) M induced submaximal relaxation resulting in no shift in short-acting beta2-adrenoceptor agonist concentration-response curves. Salmeterol but not formoterol appears to antagonize the relaxation of human contracted bronchi induced by short-acting beta2-agonists. These results obtained in vitro cannot be translated in clinical terms. This study, however, highlights the need for clinical studies on the interaction of long-acting and short-acting beta2-adrenoceptor agonists in acute severe asthma.

Therapeutic equivalence of diclofenac sustained-released 75 mg tablets and diclofenac enteric-coated 50 mg tablets in the treatment of painful osteoarthritis.

Efficacy and tolerability of diclofenac sustained-released (SR) 75 mg tablets taken b.i.d. were compared with that of enteric-coated diclofenac sodium 50 mg tablets given t.i.d. in a seven-day, randomised, double-blind, double-dummy, parallel groups study in 294 outpatients suffering from painful femorotibial or hip osteoarthritis. Primary efficacy criteria were spontaneous joint pain assessed on serial visual analogue scales during the first 36 hours and after 48 hours of treatment. The two treatments had equivalent efficacy since all the 90% confidence intervals of differences between means for pain intensity between the two groups were included within the interval (-10 mm; +10 mm). Rates of overall efficacy judged good to excellent ranged from 74.3-78.5% in both groups. One or more drug-related adverse events, mainly gastrointestinal, was reported by 24.5% and 27.2% of patients in diclofenac SR 75 mg and diclofenac 50 mg groups, respectively. Percentage of good compliance (i.e. > 90%) was higher with diclofenac SR 75 mg (p < 0.001).

A population pharmacokinetic study of alminoprofen penetration into synovial fluid.

The pharmacokinetics of alminoprofen in plasma and synovial fluid (SF) at steady state (300 mg t.i.d.) was studied in 45 patients with knee effusion. Plasma and SF samples, one each per patient, were obtained. Six groups were made according to the time of sampling after ingestion of the 13th dose: 1 h (n = 7), 2 h (n = 7), 4 h (n = 7), 6 h (n = 10), 8 h (n = 6), 12 h (n = 8). A three-compartment model was used to describe alminoprofen kinetics in plasma and SF, with two parameterizations, a 'classical' and a 'physiological' one. The non-linear mixed effect model approach was used to estimate the mean and variance of the pharmacokinetic parameters. The mean +/- SE of the estimates (coefficient of variation of interindividual variability as a percentage) were volume of distribution, 11.0 +/- 1.711 (12%); elimination rate constant, 0.236 +/- 0.025 h-1 (18%); absorption rate constant 2.80 +/- 0.31 h-1 (464%), clearance of influx into SF, 0.29 +/- 0.14 mL min-1; clearance of efflux into plasma, 0.56 +/- 0.25 mL min-1. These two clearances were not significantly different, which indicates that passive diffusion occurs in both directions. The mean +/- SD alminoprofen concentration versus time curve in plasma and SF at steady state was simulated and showed that the mean +/- SD maximal concentration in SF was 8.1 +/- 6.3 mg L-1 and was obtained 4 h after dose administration.

Pharmacokinetics of amoxicillin coadministered with a saline-polyethylene glycol solution in healthy volunteers.

The pharmacokinetics of orally administered amoxicillin were investigated in 12 healthy volunteers in a crossover design. They received either a placebo or a saline-polyethylene glycol solution (SPG) for 4 d, the last dose being given simultaneously with 1 g amoxicillin; blood samples were drawn for the next 12 h. Amoxicillin kinetics were similar in the two treatments but small differences in some pharmacokinetic parameters reached significance. The mean +/- SD area under the curve was lower with SPG (43.8 +/- 6.8 against 47.8 +/- 8.2 mg h L-1, p < 0.05) but the treatments were equivalent according to Westlake's test (95% confidence interval = 14.95%). Analysis of SPG against placebo amoxicillin absorption kinetics after fitting the data to a Weibull model revealed a longer duration of the absorption, a slower rate of absorption, and a different shape of the curve. No clinical consequences are expected from these minor variations but possible mechanisms could be relevant to other drugs.

Influence of local radiotherapy on penetration of fluconazole into human saliva.

The pharmacokinetics of fluconazole (50 mg, single oral dose) in saliva and plasma were determined for five healthy subjects and five patients who underwent radiotherapy (dose, > 45 Gy over a 6-week period) in the salivary gland area and suffered from oropharyngeal candidiasis. Saliva was collected after electrical stimulation. Fluconazole was measured by liquid chromatography. From healthy volunteers and patients, saliva and plasma were sampled from 0 to 24 h. Although fluconazole penetration kinetics were significantly slowed down in irradiated patients, saliva concentrations of fluconazole were higher than those in the plasma, except at 1 h. In the postdistribution phase, the saliva/plasma concentration ratio was in the range of 1.2 to 1.4, and there was no significant difference between healthy subjects and patients. The saliva concentration of fluconazole was over 1 mg/liter throughout the entire interval 2 to 24 h after drug intake. From these results, the clinical efficacy of fluconazole for oropharyngeal candidiasis is not expected to be less than that in subjects with normal salivary glands, provided that salivary secretion remains.

Pharmacokinetics and bactericidal activities of one 800-milligram dose versus two 400-milligram doses of intravenously administered pefloxacin in healthy volunteers.

Pefloxacin pharmacokinetics and serum bactericidal activities (SBA) against Escherichia coli and Staphylococcus aureus were compared after intravenous infusion of either a single 800-mg dose or twice-daily 400-mg doses into 16 healthy volunteers. Plasma pefloxacin concentrations were measured for up to 60 h, and SBAs were determined 1, 12, and 24 h after the start of the infusion. The mean areas under the concentration-versus-time curve for plasma were not different (138 versus 136 h.mg/liter). The mean clearances, volumes of distribution, and half-lives were also comparable. The mean (+/- standard deviation) maximal concentration after the 800-mg infusion was 12.11 +/- 1.35 versus 6.51 +/- 0.73 mg/liter after the first 400-mg infusion and 7.42 +/- 0.76 mg/liter after the second 400-mg infusion. Mean trough concentrations at 24 h were significantly different: 2.77 +/- 0.63 (800 mg) versus 1.93 +/- 0.49 (400 mg twice) mg/liter (P = 0.0007). Mean SBAs against E. coli after 800 mg of pefloxacin were higher than 1/128 (1 h), 1/32 (12 h), and 1/16 (24 h). Mean SBAs against S. aureus under the same conditions were higher than 1/64 (1 h), 1/16 (12 h), and 1/8 (24 h). Mean SBAs at 1 and 12 h were significantly higher after the 800-mg infusion than after the 400-mg infusion but were similar at 24 h for both regimens. Comparison of SBAs according to National Committee for Clinical Laboratory Standards criteria showed a similar adequacy at 24 h for both regimens against both strains. Administration of 800 mg of pefloxacin once a day is bioequivalent to 400 mg twice a day, and bactericidal activity of the 800-mg infusion is not less than that of two 400-mg infusions.