Mass spectral fragmentation of the intravenous anesthetic propofol and structurally related phenols

Simple quantification of propofol and its metabolites in blood and urine using gas chromatography-tandem mass spectrometry (GC-MS/MS)

An analytical method which was used for the simultaneous detection and quantification of propofol and its metabolites in human blood and urine by gas chromatography-tandem mass spectrometry (GC-MS/MS) was newly established and applied to authentic human samples obtained from the deceased. The QuEChERS method was employed, and then analyzed by GC-MS/MS. We separately used sulfatase and β-glucuronidase to hydrolyze the urine sample and calculated the increase of propofol and 4-hydroxypropofol before and after the hydrolysis. The results of urinary concentrations in urine from the subject were: 4.88 μg/mL for propofol, 0.53 μg/mL for 4-hydroxypropofol, 3.35 μg/mL for propofol-glucuronide, 0.31 μg/mL for the total concentration of 1-(2,6-diisopropyl-1,4-quinol)-glucuronide plus 4-(2,6-diisopropyl-1,4-quinol)-glucuronide, and 0.39 μg/mL for 4-(2,6- diisopropyl-1,4-quinol)-sulfate. The lower limit of quantification was 10 ng/mL for all determined compounds; the extraction recoveries were not less than 57.2 %. Intraday and interday precisions and accuracies were all less than 10 %. The calibration curves for propofol and 4-hydroxypropofol in human urine showed the correlation values of not less than 0.999; propofol and 4-hydroxypropofol in blood also presented good linearities in the concentration ranges of 0.1-10 μg/mL. The two compounds had good stability within 7 days at 25, 4, and -20 ℃. To our knowledge, this is the first trial to establish a simple and reliable method to simultaneously detect and quantify of propofol and its phase I and II metabolites in human blood and urine samples by GC-MS/MS.

Improving the Selectivity of the C-C Coupled Product Electrosynthesis by Using Molecularly Imprinted Polymer─An Enhanced Route from Phenol to Biphenol

We developed a procedure for selective 2,4-dimethylphenol, DMPh, direct electro-oxidation to 3,3',5,5'-tetramethyl-2,2'-biphenol, TMBh, a C-C coupled product. For that, we used an electrode coated with a product-selective molecularly imprinted polymer (MIP). The procedure is reasonably selective toward TMBh without requiring harmful additives or elevated temperatures. The TMBh product itself was used as a template for imprinting. We followed the template interaction with various functional monomers (FMs) using density functional theory (DFT) simulations to select optimal FM. On this basis, we used a prepolymerization complex of TMBh with carboxyl-containing FM at a 1:2 TMBh-to-FM molar ratio for MIP fabrication. The template-FM interaction was also followed by using different spectroscopic techniques. Then, we prepared the MIP on the electrode surface in the form of a thin film by the potentiodynamic electropolymerization of the chosen complex and extracted the template. Afterward, we characterized the fabricated films by using electrochemistry, FTIR spectroscopy, and AFM, elucidating their composition and morphology. Ultimately, the DMPh electro-oxidation was performed on the MIP film-coated electrode to obtain the desired TMBh product. The electrosynthesis selectivity was much higher at the electrode coated with MIP film in comparison with the reference nonimprinted polymer (NIP) film-coated or bare electrodes, reaching 39% under optimized conditions. MIP film thickness and electrosynthesis parameters significantly affected the electrosynthesis yield and selectivity. At thicker films, the yield was higher at the expense of selectivity, while the electrosynthesis potential increase enhanced the TMBh product yield. Computer simulations of the imprinted cavity interaction with the substrate molecule demonstrated that the MIP cavity promoted direct coupling of the substrate to form the desired TMBh product.

The Intestinal and Biliary Metabolites of Ibuprofen in the Rat with Experimental Hyperglycemia

Hyperglycemia is reported to be associated with oxidative stress. It can result in changes in the activities of drug-metabolizing enzymes and membrane-integrated transporters, which can modify the fate of drugs and other xenobiotics; furthermore, it can result in the formation of non-enzyme catalyzed oxidative metabolites. The present work aimed to investigate how experimental hyperglycemia affects the intestinal and biliary appearance of the oxidative and Phase II metabolites of ibuprofen in rats. In vivo studies were performed by luminal perfusion of 250 μM racemic ibuprofen solution in control and streptozotocin-treated (hyperglycemic) rats. Analysis of the collected intestinal perfusate and bile samples was performed by HPLC-UV and HPLC-MS. No oxidative metabolites could be detected in the perfusate samples. The biliary appearance of ibuprofen, 2-hydroxyibuprofen, ibuprofen glucuronide, hydroxylated ibuprofen glucuronide, and ibuprofen taurate was depressed in the hyperglycemic animals. However, no specific non-enzymatic (hydroxyl radical initiated) hydroxylation product could be detected. Instead, the depression of biliary excretion of ibuprofen and ibuprofen metabolites turned out to be the indicative marker of hyperglycemia. The observed changes impact the pharmacokinetics of drugs administered in hyperglycemic individuals.

Rapid Analysis of Volatile Phenols from Grape Juice by Immersive Sorbent Sheet Extraction Prior to Direct Analysis in Real-Time Mass Spectrometry (DART-MS)

Poly(dimethylsiloxane)-based thin-film sorbent sheets (SPMESH) have previously been used for parallel headspace (HS) extraction prior to direct analysis in real-time mass spectrometry (DART-MS) for rapid quantitation of odorants in complex matrices. However, HS-SPMESH extraction is poorly suited for less volatile odorants, e.g., volatile phenols. This report describes modifications to the previous SPMESH extraction device, which make it amenable to parallel extraction of low-volatility analytes from multiwell plates under direct immersion (DI) conditions. Optimization and validation of the DI-SPMESH-DART-MS approach were performed on four volatile phenols (4-ethylphenol, 4-ethylguaiacol, 4-methylguaiacol, and guaiacol) of relevance to the quality of grape juices. Negative-ion mode DART-MS spectra showed a series of oxygenated adducts [M + nO - H]^- for all analytes, but isobaric interferences could be limited for three of the four analytes by selecting an appropriate MS/MS transition. Signal suppression from nonvolatiles (sugars, acids) could be overcome by a rinse step. DI-SPMESH-DART-MS analysis of 24 samples could be performed in ∼45 min (30 min extraction, 16 min DART analysis) with 0.5-3 μg/L detection limits in aqueous and model juice solutions. In real grape juices (n = 5 cultivars), good accuracy (72-137%) could be achieved for two of the four volatile phenols initially investigated, 4-ethylphenol and 4-ethylguaiacol. However, poor accuracy was observed for guaiacol in some cultivars, and 4-methylguaiacol could not be quantitated due to interferences with other volatile phenols. Despite these limitations, DI-SPMESH-DART-MS/MS may be useful for prescreening a large number of samples prior to more selective conventional analyses.

Fluoride-assisted liquid chromatography-tandem mass spectrometry method for simultaneous analysis of propofol and its metabolites without derivatization in urine

The misuse of propofol for recreational purposes has become a serious social issue. Accordingly, practical and sensitive analytical methods to investigate the chronic abuse and toxicity of propofol are required. However, current propofol determination methods using liquid chromatography-mass spectrometry (LC-MS/MS) suffer from problems associated with loss in sample preparation due to its volatility and its poor ionization efficiency and collision-induced dissociation in mass spectrometry. Herein, we have developed a sensitive and accurate fluoride-assisted LC-MS/MS method combined with direct-injection for propofol determination. Ionization via fluoride-ion attachment/induced deprotonation, effected by ammonium fluoride in the mobile phase, was found to dramatically improve the sensitivity of propofol without derivatization. Furthermore, direct injection without derivatization enables the simultaneous analysis of propofol and its phase II metabolites without analyte loss. The optimal concentration of ammonium fluoride in the mobile phase was found to be 1 mM under methanol conditions. The linearity is good (R² ≥ 0.999) and the intra- and inter-day precisions for propofol determination are between 1.9 and 8.7%. The accuracies range from 87.5% to 105.4% and the limits of detection and quantitation for propofol in urine are 0.15 and 0.44 ng mL^-1, respectively. The present method was successfully applied to human urine and showed a sufficient sensitivity to determine propofol and five phase II metabolites over 48 h in human urine after administration. Consequently, the fluoride-assisted LC-MS/MS method was demonstrated to be sensitive, accurate, and practical for the determination of propofol and its metabolites.

Matrix-assisted laser desorption/ionization time-of-flight/time-of-flight tandem mass spectrometry (negative ion mode) of French Oak lignin: A novel series of lignin and tricin derivatives attached to carbohydrate and shikimic acid moieties

RATIONALE

We report the top-down lignomic analysis of the virgin released lignin (VRL) small oligomers obtained from French Oak wood.

METHODS

We have used MALDI-TOF-MS in the negative ion mode for the analysis of the complex mixture of lignin oligomers extracted from French Oak wood. High-energy CID-TOF/TOF-MS/MS analyses were used to support the postulated precursor ion structures.

RESULTS

Twenty compounds were identified using MALDI-TOF-MS/MS of the VRL extracted from French Oak wood: seven tricin derivatives and/or flavonoids, three syringylglycerol derivatives, two syringol derivatives, two flavonolignin derivatives, and six miscellaneous compounds: luteoferol, lariciresinol isomer, 5-hydroxy guaiacyl derivative, syringyl -C₁₀ H₁₀ O₂ dimer, trihydroxy benzaldehyde derivative, and aryl tetralin lignan derivative. Most of the identified compounds were in the form of carbohydrate and/or shikimic acid complexes.

CONCLUSIONS

The analysis of this complex mixture led to the identification of a series of lignin dimers, novel lignin-carbohydrate complexes (LCC), and unique tricin derivatives linked to different types of carbohydrates and shikimic acid moieties. This finding supports the presence of lignin-carbohydrate complexes in the isolated VRL. These analyses also showed that French Oak lignin is abundant in syringol moieties present in the lignin syringyl units or tricin derivatives. Moreover, the identification of some lignin-carbohydrate and/or flavonoid-shikimic acid complexes could provide new insight into the relationship between the biosynthesis of lignin and tricin.

The Molecular Mechanisms Associated with the Effects of Propofol in a Rat Model of Pain Due to Inflammation Following Injection with Complete Freund's Adjuvant

Background

This study aimed to investigate the molecular mechanisms associated with the effects of propofol in a rat model of pain due to inflammation following subcutaneous injection with complete Freund’s adjuvant (CFA).

Material/Methods

Sprague-Dawley rats were injected subcutaneously in the paw with CFA. Propofol or saline was administered by tail vein injection. After CFA treatment for 0 hours, 4 hours, 1 day, 4 days, 7 days, and 14 days, the behavior of the rats was assessed. An enzyme-linked immunosorbent assay (ELISA) measured serum levels of proinflammatory cytokines, including tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and IL-6. Western blot and the quantitative reverse-transcription polymerase chain reaction (qRT-PCR) were used to detect levels of p38MAPK and NF-κB related mRNA and proteins, including p-p38, p38, p65, p-p65, NOD-like receptor family protein 3 (NLRP3), apoptosis-associated speck-like protein (ASC) and caspase-1 in rat spinal cord tissues.

Results

Injection of CFA significantly reduced the mechanical withdrawal threshold (MWT), thermal withdrawal latency (TWL), and frequency responses to cold stimulation. Propofol treatment significantly reduced serum levels of TNF-α, IL-1β, and IL-6. Protein expression levels of p-p38 and p-p65 were upregulated in the rat model, which were inhibited by propofol treatment. CFA injection increased the expression levels of NLRP3, ASC, and caspase-1 in the spinal cord tissues of rats, which were reduced by propofol treatment.

Conclusions

In a rat model of pain following subcutanous injection with CFA, propofol reduced CFA-induced pain and inhibited the inflammatory response through the p38MAPK-nuclear factor-κB (NF-κB) pathway and the NLRP3 inflammasome.

Characterization of aerosol nitroaromatic compounds: Validation of an experimental method

The analytical capabilities associated with the use of silylation reactions have been extended to a new class of organic molecules, nitroaromatic compounds (NACs). These compounds are a possible contributor to urban particulate matter of secondary origin which would make them important analytes due to their (1) detrimental health effects, (2) potential to affect aerosol optical properties, and (3) and usefulness for identifying PM_2.5 from biomass burning. The technique is based on derivatization of the parent NACs by using N,O-bis-(trimethylsilyl)-trifluoro acetamide, one of the most prevalent derivatization reagent for analyzing hydroxylated molecules, followed by gas chromatography-mass spectrometry using electron ionization (EI) and methane chemical ionization (CI). This method is evaluated for 32 NACs including nitrophenols, methyl-/methoxy-nitrophenols, nitrobenzoic acids, and nitrobenzyl alcohols. Electron ionization spectra were characterized by a high abundance of ions corresponding to [M⁺ ] or [M⁺  - 15]. Chemical ionization spectra exhibited high abundance for [M⁺  + 1], [M⁺  - 15], and [M⁺  + 29] ions. Both EI and CI spectra exhibit ions specific to nitro group(s) for [M⁺  - 31], [M⁺  - 45], and [M⁺  - 60]. The strong abundance observed for [M⁺ ] (EI), [M⁺  - 15] (EI/CI), or [M⁺  + 1] (CI) ions is consistent with the high charge stabilizing ability associated with aromatic compounds. The combination of EI and CI ionization offers strong capabilities for detection and identification of NACs. Spectra associated with NACs, containing hydrogen, carbon, oxygen, and nitrogen atoms only, as silylated derivatives show fragment/adduct ions at either (a) odd or (b) even masses that indicate either (a) odd or (b) even number of nitro groups, respectively. Mass spectra associated with silylated NACs exhibited 3 distinct regions where characteristic fragmentation with a specific pattern associated with (1) ─OH and/or ─COOH groups, (2) ─NO₂ group(s), and (3) benzene ring(s). These findings were confirmed with applications to chamber aerosol and ambient PM_2.5 .

In vitro and in vivo metabolite identification of a novel benzimidazole compound ZLN005 by LC-MS/MS

RATIONALE

A novel benzimidazole compound ZLN005 was previously identified as a transcriptional activator of peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α) in certain metabolic tissues. Upregulation of PGC-1α by ZLN005 has been shown to have beneficial effect in a diabetic mouse model and in a coronary artery disease model in vitro. ZLN005 could also have therapeutic potential in neurodegenerative diseases involving down-regulation of PGC-1α. Given the phenotypic efficacy of ZLN005 in several animal models of human disease, its metabolic profile was investigated to guide the development of novel therapeutics using ZLN005 as the lead compound.

METHODS

ZLN005 was incubated with both rat and human liver microsomes and S9 fractions to identify in vitro metabolites. Urine from rats dosed with ZLN005 was used to identify in vivo metabolites. Extracted metabolites were analyzed by LC-MS/MS using a hybrid linear ion trap triple quadrupole mass spectrometer under full scan, enhanced product ion scan, neutral loss scan and precursor scan modes. Metabolites in plasma and brain of ZLN005-treated rats were also profiled using multiple reaction monitoring.

RESULTS

Identified in vitro transformations of ZLN005 include mono- and dihydroxylation, further oxidation to carboxylic acids, and mono-O-glucuronide and sulfate conjugation to hydroxy ZLN005 as well as glutathione conjugation. Identified in vivo metabolites are mainly glucuronide and sulfate conjugates of dihydroxyl, carboxyl, and hydroxy acid of the parent compound. The parent compound as well as several major phase I metabolites were found in rat plasma and brain.

CONCLUSIONS

Using both in vitro and in vivo methods, we elucidated the metabolic pathway of ZLN005. Phase I metabolites with hydroxylation and carboxylation, as well as phase II metabolites with glucuronide, sulfate and glutathione conjugation, were identified.

On the origin of the methyl radical loss from deprotonated ferulic and isoferulic acids: electronic excitation of a transient structure

Formation of radical fragments from even-electron ions is an exception to the "even-electron rule". In this work, ferulic acid (FA) and isoferulic acid (IFA) were used as the model compounds to probe the fragmentation mechanisms and the isomeric effects on homolytic cleavage. Elimination of methyl radical and CO2 are the two competing reactions observed in the CID-MS of [FA - H](-) and [IFA - H](-), of which losing methyl radical violates the "even-electron rule". The relative intensity of their product ions is significantly different, and thereby the two isomeric compounds can be differentiated by tandem MS. Theoretical calculations indicate that both the singlet-triplet gap and the excitation energy decrease in the transient structures, as the breaking C-O bond is lengthened. The methyl radical elimination has been rationalized as the intramolecular electronic excitation of a transient structure with an elongating C-O bond. The potential energy diagrams, completed by the addition of the energy barrier of the radical elimination, have provided a reasonable explanation of the different CID-MS behaviors of [FA - H](-) and [IFA - H](-).

Fragmentation reactions of phenoxide anions: deprotonated Dinoterb and related structures

Dinoterb (6-t-butyl-2,4-dinitrophenol), 1, Dinoseb (6-secbutyl-2,4-dinitrophenol), 2, TBP (2-t-butylphenol), 3, and DNP (2,4-dinitrophenol), 4, have been analyzed by electrospray ionization in the negative mode (ESI-N) - tandem mass spectrometry. Nominal laboratory collision energy was varied from zero to 60 eV during the experiments. Apparent fragmentation energies were estimated from a parametric fitting of the collision efficiency curves. In parallel, fragmentation mechanisms of the deprotonated molecules [M-H](-) were explored using quantum chemistry modeling at the B3LYP/6-31 + G(d,p) level. A major fragmentation of the [M-H](-) ions of Dinoterb and Dinoseb is elimination of an alcohol molecule. This reaction is shown to involve one oxygen atom originating from a nitro group rather than the phenoxide moiety. Eliminations of NO, C(4) and CH(2) = C(CH(3))(2), i.e. reactions involving significant rearrangements, constitute the major part of the other fragmentation pathways observed from [3-H](-) and [4-H](-) ions.

Hemodynamic characteristics of midazolam, propofol, and dexmedetomidine in healthy volunteers

STUDY OBJECTIVE

To study the effect of intravenous (IV) sedation on blood pressure (BP), heart rate (HR), and respiratory rates (RR) to determine if IV sedatives differ with respect to their effect on BP, HR, and RR.

DESIGN

Prospective, randomized, single-blinded, placebo-controlled study.

SETTING

Monitored patient care room at a clinical research center.

SUBJECTS

60 healthy ASA physical status 1 volunteers.

INTERVENTIONS

Subjects were randomized to receive, in increasing doses, one of three IV sedatives: propofol, midazolam, or dexmedetomidine; or saline control.

MEASUREMENTS

Blood pressure (systolic, diastolic), HR, and RR were recorded.

MAIN RESULTS

A significant dose-dependent BP reduction occurred with dexmedetomidine and, to a lesser degree, with propofol; and there was good agreement of predicted versus measured drug concentrations for all sedatives. Blood pressure and HR of participants who received midazolam did not change.

CONCLUSIONS

When administered in sedative doses, dexmedetomidine and, to a lesser extent, midazolam, reduces BP in a dose-dependent fashion. Dexmedetomidine also reduces HR. Midazolam does not affect BP or HR.

Determination of HX0969w in Rabbit Whole Blood by Liquid Chromatography—Tandem Mass Spectrometry and its Application in a Pharmacokinetic Study

HX0969w is a novel carboxylate ester prodrug of propofol. After intravenous administration of HX0969w, the compound is rapidly hydrolyzed to its active metabolite propofol. A liquid chromatography–tandem mass spectrometry method with electrospray ionization has been developed for determination of HX0969w in rabbit whole blood. Protein precipitation with methanol was used for sample preparation and 7-hydroxycoumarin served as internal standard. The standard curve ranged from 50.1 ng mL−1. to 15,030 ng mL−1. The lower limit of quantification for HX0969w was 50.1 ng mL−1. The intra- and inter-day accuracies were within ±10% and precisions were below 5.52%. The method was successfully applied to samples from a rabbit pharmacokinetic study.

Thromboelastographic and pharmacokinetic profiles of micro- and macro-emulsions of propofol in swine

PURPOSE

Compared with traditional macroemulsion propofol formulations currently in clinical use, microemulsion formulations of this common intravenous anesthetic may offer advantages. The pharmacokinetics and coagulation effects as assessed by thromboelastography of these formulations were characterized in swine.

METHODS

Yorkshire swine (20-30 kg, either sex, n=15) were sedated, anesthetized with isoflurane, and instrumented to obtain a tracheostomy, internal jugular access and carotid artery catheterization. Propofol (2 mg/kg, 30 s) was administered as a macroemulsion (10 mg/ml; Diprivan; n=7) or a custom (2 mg/kg, 30 s) microemulsion (10 mg/ml; n=8). Arterial blood specimens acquired pre- and post-injection (1 and 45 min) were used for thromboelastography. Arterial blood specimens (n=12 samples/subject, 60 min) were serially collected, centrifuged and analysed with solid-phase extraction with UPLC to determine propofol plasma concentrations. Non-compartmental pharmacokinetic analysis was applied to plasma concentrations.

RESULTS

No changes were noted in the thromboelastographic R time (p=0.74), K time (p=0.41), alpha angle (p=0.97), or maximal amplitude (p=0.71) for either propofol preparation. Pharmacokinetic parameters k (p=0.45), t(1/2) (p=0.26), C(o) (p=0.89), AUC(0-infinity) (p=0.23), CL (p=0.14), MRT (p=0.47), V(ss) (p=0.11) of the two formulations were not significantly different.

CONCLUSION

The microemulsion and macroemulsion propofol formulations had similar pharmacokinetics and did not modify thromboelastographic parameters in swine.

Characterization of an exception to the 'even-electron rule' upon low-energy collision induced decomposition in negative ion electrospray tandem mass spectrometry

Electrospray-generated precursor ions usually follow the 'even-electron rule' and yield 'closed shell' fragment ions. We characterize an exception to the 'even-electron rule.' In negative ion electrospray mass spectrometry (ES-MS), 2-(ethoxymethoxy)-3-hydroxyphenol (2-hydroxyl protected pyrogallol) easily formed a deprotonated molecular ion (M-H)(-) at m/z 183. Upon low-energy collision induced decomposition (CID), the m/z 183 precursor yielded a radical ion at m/z 124 as the base peak. The radical anion at m/z 124 was still the major fragment at all tested collision energies between 0 and 50 eV (E(lab)). Supported by computational studies, the appearance of the radical anion at m/z 124 as the major product ion can be attributed to the combination of a low reverse activation barrier and resonance stabilization of the product ions. Furthermore, our data lead to the proposal of a novel alternative radical formation pathway in the protection group removal of pyrogallol.

Quantitative measurement of propofol and in main glucuroconjugate metabolites in human plasma using solid phase extraction–liquid chromatography–tandem mass spectrometry

A high-performance liquid chromatographic method coupled with tandem mass spectrometry detection has been developed for the determination of propofol and its main glucuroconjugate metabolites (propofol-glucuronide (PG), 1-quinol-glucuronide (1-QG) and 4-quinol-glucuronide (4-QG) in human plasma. All compounds were extracted with a single solid phase extraction procedure using Max Oasis cartridges. Propofol and thymol (internal standard) were analyzed using a C8 reversed-phase column with a mobile phase consisting of methanol-water (75:25, v/v) containing 0.025% NH(4)OH. Chromatography of glucuroconjugate metabolites and phenyl-beta-d-glucuronide (internal standard) was performed using a hydrophilic interaction liquid chromatography (HILIC) and a mixture of acetonitrile/water/ammonium acetate buffer (100 mM, pH 5, 87/1/12, v/v/v). Both chromatographic separations were achieved in isocratic mode allowing a rapid analysis without re-equilibration of the phase. The method is specific and sensitive with a range of 10-1500 ng mL(-1) for propofol and 1-QG, 20-3000 ng mL(-1) for PG and 25-3750 ng mL(-1) for 4-QG. The regression curves were linear for all compounds. The method is accurate and precise with intra-assay and inter-assay precision <8% and bias < or =6% for all compounds. This assay has allowed the successful measurement of propofol and its main glucuroconjugate metabolites in human plasma from 24 patients undergoing anaesthesia for elective partial hepatectomy surgery.

Anesthetic properties of a propofol microemulsion in dogs

Microemulsions of propofol with nanometer droplet diameter are alternatives to soybean macroemulsions for inducing anesthesia, and may have important advantages. We used a propofol (10 mg/mL) microemulsion (particle diameter 24.5 +/- 0.5 nm) and a commercial macroemulsion to induce anesthesia in dogs (n = 10) using a randomized, crossover design separated by a 7-day rest interval. The end points were loss of leg withdrawal after a toe pinch and changes in vital signs. Venous blood samples were acquired at multiple times to measure plasma propofol concentrations and indices of erythrocytes, leukocytes, and coagulation. All dogs were rendered insensitive to pain followed by successful recovery without noticeable complications. Comparing indices between microemulsion and macroemulsion formulations, no differences were noted with respect to dose (10.3 +/- 1.2 and 9.7 +/- 1.6 mg/kg, respectively, P = 0.39), time to induction (1.0 +/- 0.1 and 1.0 +/- 0.2 min, P = 0.39), time to recovery (17.4 +/- 4.6 and 18.2 +/- 3.8 min, P = 0.70), heart rate (P = 0.62), arterial blood pressure (P = 0.81), respiratory rate (P = 0.60), hemogram variables, prothrombin time (P = 0.89), activated partial thromboplastin time (P = 0.76), fibrinogen concentration (P = 0.52), platelet concentration (P = 0.55), or plasma propofol concentrations (P = 0.20). Induction with a propofol microemulsion or macroemulsion did not significantly vary with respect to vital signs, the hemogram, clotting variables, and plasma propofol concentrations.