Prediction methods of drug-drug interactions of non-oral CYP3A4 substrates based on clinical interaction data after oral administrations - Validation with midazolam, alfentanil, and verapamil after intravenous administration and prediction for blonanserin transdermal patch.

Drug-drug interactions (DDI) have been examined for various drugs for oral use, but less for non-oral applications. This study provides DDI prediction methods for non-orally administered CYP3A4 substrates based on clinical DDI data of oral dosages. Gut availability (Fg) and fraction contribution of CYP3A4 to hepatic intrinsic clearance (fmCYP3A4) were predicted by AUC ratio (AUCR) in oral DDI study with/without grapefruit juice, and alteration in intrinsic clearances with/without ketoconazole, respectively. AUCRs of non-orally administered CYP3A4 substrates with/without inhibitors or inducers were predicted with the estimated Fg, fmCYP3A4 and changes in liver CYP3A4 activities with inhibitors/inducers predicted using Simcyp library. DDIs of intravenously administered midazolam and alfentanil with CYP3A4 inhibitors/inducers could be predicted well by this method with predicted AUCRs within ±64% of observed values. Moreover, maximum DDIs with strong CYP3A4 inducers could be predicted by comparing hepatic clearance with hepatic blood flow, as hepatic blood flow indicates the possible maximum hepatic clearance after strong enzyme induction. Predicted AUCRs of midazolam, alfentanil and R- and S-verapamil were less than, but not far from observed ratios, suggesting good conservative prediction. These methods were applied to blonanserin transdermal patch, suggesting much smaller interaction with CYP3A4 inhibitors/inducers compared to oral dosage of blonanserin.

Impurity profiling of alfentanil hydrochloride by liquid chromatography/quadrupole time-of-flight high-resolution mass spectrometric techniques for drug enforcement.

RATIONALE: Fentanyl and its analogues play important roles in the hospital and clinic setting as anesthetics. However, illicitly manufactured fentanyl as well as the new psychoactive substances (NPS) account for 30% of all deaths in the United States. Since fentanyl derivatives and NPS are designed to produce similar effects, their related substances are similar or even have the same active groups. A comprehensive analysis of the related substances of alfentanil hydrochloride can provide a basis for the identification and supervision of fentanyl derivatives and NPS. METHODS: A liquid chromatography/quadrupole time-of-flight tandem mass spectrometry (LC/QTOF-MS/MS) method was developed for the separation and characterization of related substances in alfentanil hydrochloride. Degradation studies were conducted according to the ICH-prescribed stress conditions. The compounds were identified mainly through positive electrospray ionization QTOF high-resolution mass spectrometric measurements of the accurate masses of the precursor and product ions and their calculated elemental compositions. Their formation mechanisms were also discussed. RESULTS: Seventeen related substances were detected in alfentanil hydrochloride and its stressed samples. Among them, nine were process-related substances and the other eight were degradation products. The stress study results demonstrated that alfentanil hydrochloride was unstable under acid, alkaline, and oxidative stress conditions, while relatively stable under dry photolytic and thermal stress conditions. Alfentanil hydrochloride was most susceptible for degradation at the N-phenylpropanamide and piperidine sites. CONCLUSIONS: Process-related alfentanil hydrochloride compounds are useful for determination of synthetic routes and entangling of fentanyl analogues. The stress study results can provide a sound scientific basis for the waste water monitoring of alfentanil. These results are important for routine quality control in the manufacturing and storage of alfentanil hydrochloride, as well as for drug enforcement of fentanyl and its analogues.

Investigating Power Density and the Degree of Nonlinearity in Intrinsic Components of Anesthesia EEG by the Hilbert-Huang Transform: An Example Using Ketamine and Alfentanil.

Empirical mode decomposition (EMD) is an adaptive filter bank for processing nonlinear and non-stationary signals, such as electroencephalographic (EEG) signals. EMD works well to decompose a time series into a set of intrinsic mode functions with specific frequency bands. An IMF therefore represents an intrinsic component on its correspondingly intrinsic frequency band. The word of 'intrinsic' means the frequency is totally adaptive to the nature of a signal. In this study, power density and nonlinearity are two critical parameters for characterizing the amplitude and frequency modulations in IMFs. In this study, a nonlinearity level is quantified using degree of waveform distortion (DWD), which represents the characteristic of waveform distortion as an assessment of the intra-wave modulation of an IMF. In the application of anesthesia EEG analysis, the assessments of power density and DWD for a set of IMFs represent dynamic responses in EEG caused by two different anesthesia agents, Ketamine and Alfentanil, on different frequency bands. Ketamine causes the increase of power density and the decrease of nonlinearity on γ-band neuronal oscillation, which cannot be found EEG responses of group B using Alfentanil. Both agents cause an increase of power density and a decrease of nonlinearity on ß-band neuronal oscillation accompany with a loss of consciousness. Moreover, anesthesia agents cause the decreases of power density and nonlinearity (i.e. DWD) for the low-frequency IMFs.

Effect of mild hypocapnia on hemodynamic and bispectral index responses to tracheal intubation during propofol anesthesia in children.

The purpose of this study was to investigate the effect of mild hypocapnia on hypertension and arousal response after tracheal intubation in children during propofol anesthesia. Forty-four children, American Society of Anesthesiologists physical status I-II patients, aged 3-9 years were randomly allocated to either the normocapnia group [end-tidal carbon dioxide tension (ETCO2=35 mmHg, n=22)] or the hypocapnia group (ETCO2=25 mmHg, n=22). Anesthesia was induced with propofol 2.5 mg/kg. Five minutes after the administration of rocuronium 0.6 mg/kg, laryngoscopy was attempted. The mean arterial pressure (MAP), heart rate (HR), SpO2 and bispectral index (BIS) were measured during induction and intubation periods. The maximal change in the BIS with tracheal intubation (ΔBIS) was defined as the difference between the baseline value and the maximal value within the first 5 min after intubation. Before tracheal intubation, the change in BIS over time was not different between the groups. After tracheal intubation, the changes in the MAP, HR and BIS over time were not significantly different between the groups. The mean value±SD of ΔBIS was 5.7±5.2 and 7.4±5.5 in the normocapnia and hypocapnia groups, respectively, without any intergroup difference. This study showed that mild hypocapnia did not attenuate hemodynamic and BIS responses to tracheal intubation in children during propofol anesthesia. Our results suggested that hyperventilation has no beneficial effect on hemodynamic and arousal responses to tracheal intubation in children.

Configuration and conformation of alfentanil hydrochloride. Conformational study by NMR and theoretical calculations.

The configurational and conformational structure of alfentanil hydrochloride (1) was studied by nuclear magnetic resonance and theoretical calculations. Compound 1 is best described by equilibrium between two stereoisomeric piperidinium rings with the N-substituent always being in equatorial position. Nuclear magnetic resonance spectra demonstrate that, depending on the solvent, 1 adopts the conformation with an axial methoxymethylene group. Computations were crucial in determining the importance of the transannular attractive interaction between the positive charge at the piperidinium N-atom and the methoxymethyl group in position 4.

Miniaturized hollow fibre assisted liquid-phase microextraction and gas chromatography for determination of trace concentration of sufentanil and alfentanil in biological samples.

A simple and highly sensitive method that involves miniaturized hollow fibre assisted liquid-phase microextraction with gas chromatography-flame ionization detector was developed for the determination of trace concentration of sufentanil and alfentanil in biological samples. These drugs were extracted from 5 ml of aqueous solution with pH 10.0 into an organic extracting solvent (1-octanol) impregnated in the pores and lumen of a hollow fibre. After extraction for a prescribed time, 2.0 µl of the extraction solvent was injected directly in to the GC injection port. Under the optimized conditions, (1-octanol as extracting solvent, stirring rate of 700 rpm, 15% (w/v) salt addition, pH 10.0 and 25 min sampling time at 50 °C) large enrichment factors of 535 and 420 were achieved for sufentanil and alfentanil, respectively. Dynamic linear ranges were in the range of 0.05 to 500 ng/ml for sufentanil and 0.1 to 500 ng/ml for alfentanil. Limits of detection 0.01 and 0.02 ng/ml were obtained for sufentanil and alfentanil, respectively. The percent relative intra-day and inter-day standard deviations were found to be less than 8.4% (n = 5). Finally, this method was successfully applied for the separation, preconcentration and determination of trace concentration of sufentanil and alfentanil in plasma and urine samples.

Determination of fentanyl, metabolite and analogs in urine by GC/MS.

A rapid and sensitive method for the simultaneous determination of alfentanyl, sufentanyl and fentanyl (and its major metabolite norfentanyl) in urine was developed and validated. The method involved a liquid-liquid extraction in alkaline conditions, derivatization with pentafluoropropionic anhydride to improve the sensitivity for norfentanyl and subsequent analysis in GC/MS. The LODs are 0.08 ng ml(-1) for all substances (0.04 ng ml(-1) for alfentanyl). Intra- and inter-day precision coefficient of variation was always below 15%; mean relative error (accuracy) was always below 15%. The method was linear for all analytes, with quadratic regression of calibration curves always higher than 0.99. The method was applied to real samples of subjects who had received therapeutic doses of fentanyl, showing its suitability for the determination of low levels of these substances. The method was also applied to a subject whose death was attributed to fentanyl overdose.

Identification of fentanyl, alfentanil, sufentanil, remifentanil and their major metabolites in human urine by liquid chromatography/tandem mass spectrometry for doping control purposes.

Since January 2005, the list of prohibited substances established by the World Anti-Doping Agency prohibits the opioid agent fentanyl as well as its related drugs in professional and amateur sports. Fast, reliable and robust analytical assays are required that allow the sensitive determination of these compounds or respective metabolites in human urine, and liquid chromatography interfaced to mass spectrometry has proven to be a suitable and powerful tool for drug testing for several years. A screening and confirmation method was developed that enables the identification of fentanyl, alfentanil, remifentanil and sufentanil as well as their N-dealkylated or de-esterified metabolites utilizing solid-phase extraction of a 2 mL urine aliquot followed by LC-electrospray-MS/MS analysis. The procedure was validated in terms of recovery (95.8-104.9%), lower limit of detection (0.5 ng mL-1), specificity and interday precision (3.9-19.8%) for the four opioid drugs and the metabolic product norfentanyl. In addition, the mass spectrometric behavior of fentanyl after electrospray ionization and collision-induced dissociation was studied by synthesis and analysis of structurally related compounds, and dissociation pathways were proposed allowing the characterization of target analytes and corresponding metabolites.

Stability of sufentanil in human plasma samples.

The stability of sufentanil in human plasma kept under various storage conditions was investigated. Extraction was performed using solid phase extraction with new mixed-mode cation exchange Oasis MCX columns; quantification was carried out using gas chromatography equipped with a mass spectrometry detector. When plasma was left at 4 degrees C in nonsilanized tubes, concentrations of sufentanil decreased significantly during the first hour. In plasma samples kept at -25 degrees C for 8 hours in nonsilanized glass tubes, a significant decrease of sufentanil concentrations was found, with an average loss of 10.1% of the initial concentration. A significant decrease occurred when plasma was kept in silanized glass tubes for 12 hours at -25 degrees C. The current study emphasizes the importance of sampling and storage conditions for an accurate determination of sufentanil concentration in plasma.

Effect of molecular charge on intestinal epithelial drug transport: pH-dependent transport of cationic drugs.

The aim of this study was to investigate the effect of ionization on drug transport across the intestinal epithelium in order to include this effect in structure-absorption relationships. The pH-dependent permeation of one rapidly (alfentanil) and one slowly (cimetidine) transported basic model drug across Caco-2 cell monolayers was investigated. Both drugs had pK(a)values in the physiological pH range. The permeability coefficients (P(c)) of the model drugs were obtained at varying apical buffer pHs, thus varying the degree of drug ionization (from 5 to 95%). The relationship between P(c) and the fraction of the drug in un-ionized form (f(u)) was analyzed to delineate the permeability coefficients of the un-ionized (P(c,u)) and ionized (P(c,i)) forms of the drugs. Theoretical estimates of the pK(a) values were also calculated from ionization energies for each model compound. For both drugs, a linear increase in P(c) was observed with increasing f(u). Transport of the un-ionized form was 150- and 30-fold more rapid than transport of the ionized form for alfentanil and cimetidine, respectively. However, when f(u) <0.1, the contribution of the ionized form was significant. Because f(u) is <0.1 over the entire physiological pH range for a large number of drugs, these results will have implications on predictions of in vivo intestinal drug absorption both from in vitro studies in cell cultures and from computed structural properties of drug molecules.

Development of a gas chromatographic-mass spectrometric drug screening method for the N-dealkylated metabolites of fentanyl, sufentanil, and alfentanil.

A sensitive, specific urinary assay for fentanyl, sufentanil, and alfentanil based on their N-dealkylated metabolites is described. Norfentanyl, norsufentanil-noralfentanil, and 2H5-norfentanyl are synthesized and characterized by standard analytical techniques. Derivatization of these secondary amines to yield the pentafluorobenzamides produces stable products with good gas chromatographic properties and unique, high-mass fragments in their mass spectra. These properties are utilized to develop a drug screening procedure based on gas chromatography-mass spectrometry to detect these major metabolites in human urine. The metabolites are isolated from urine samples by a liquid-liquid extraction procedure. The method allows for detection of metabolite concentrations as low as 0.3 ng/mL.

Quantitative analysis of fentanyl in pharmaceutical preparations by gas chromatography-mass spectrometry.

Fentanyl (1-[2-phenethyl]-4-N-[N-propionylanilino]piperidine) is a potent synthetic opiate commonly used for surgical analgesia and sedation. Reports of abuse of this highly addictive drug among health care personnel have prompted the need to verify the concentration in the unused portion of single-dose ampules returned to the pharmacy. We describe a simple quantitative method for the analysis of fentanyl citrate (Sublimaze) in syringes returned to the pharmacy following surgery. Fentanyl citrate (0.1 mL) and 2H5-fentanyl (internal standard, 0.05 mL, 100 mg/L) were extracted with Toxi-A tubes (Toxi-Lab, Irvine, CA) and analyzed by gas chromatography-mass spectrometry. Calibration was linear from 1 to 60 mg/L (correlation coefficient of 0.997, n = 13) and had a limit of detection of 0.4 mg/L. Mean recovery at concentrations from 5 to 50 mg/L was 89% (range, 69-104%). No interferences were found with morphine, ketamine, midazolam, sufentanil, or alfentanil. These drugs were not selected for their potential chromatographic interference but for their availability in surgical syringes. This assay is useful in verifying that any unused fentanyl is discarded according to narcotic regulations, thereby avoiding the possibility of diversion for illicit consumption.

Use of refractometry to identify opioid-containing solutions.

The purpose of this laboratory study was to assess the value of refractometry in identifying the contents of a variety of opioid-containing solutions. A hand-held refractometer was used to document the refraction produced by the undiluted contents of alfentanil, fentanyl, morphine, sufentanil ampoules and by solutions of Ringer's lactate, 0.9% saline, 3.3% dextrose in 0.3% saline, and distilled water. Each opioid was then serially diluted in serial 1:2, 1:4, and 1:8 dilutions in each of these solutions and the refractions of each determined. Based on this information, blinded identification of various diluted opioid solutions was attempted. Refractometer values for undiluted fentanyl and sufentanil were identical with those for distilled water. Those for undiluted alfentanil and morphine were almost identical with each other and with 1:2 and 1:4 dilutions of either drug in Ringer's lactate or 0.9% saline. We conclude that refractometry is an unreliable screening method to detect tampering with opioid solutions.

Profiles of opioid analgesia in humans after intravenous bolus administration: alfentanil, fentanyl and morphine compared on experimental pain.

This report examines the relationship of plasma drug concentration to analgesic effect following bolus doses of alfentanil, fentanyl and morphine and assesses individual differences in analgesic response among volunteers. We predicted that the 3 opioids would yield disparate analgesic profiles because their physicochemical and pharmacokinetic characteristics differ. Ten healthy volunteers received intravenous bolus doses of either alfentanil, fentanyl, morphine or normal saline on different days. We stimulated their teeth electrically and measured brain evoked potential (EP) and pain report (PR) repeatedly over 2 h to assess analgesic effect. Concurrently, we drew 18 blood samples to assess opioid plasma concentrations during the test period. The relationship between opioid plasma concentration and analgesic effect was well defined for alfentanil but ambiguous for morphine. Fentanyl exhibited a marked hysteresis. We observed noteworthy individual differences in analgesic response with all 3 drugs but these differences were greatest for morphine and least for alfentanil. Inter- and intrasubject variability in analgesic response across drugs is related to the physicochemical properties of the drugs tested.