Preparation of phenylephrine 3-O-sulfate as the major in vivo metabolite of phenylephrine to facilitate its pharmacokinetic and metabolism studies.

INTRODUCTION: The in vivo disposition and metabolism of phenylephrine have not been establishedby previous analytical methods and there is a lack of available standards for quantitating the metabolites. METHODS: We pursued and compared the preparation of sulfation metabolites of phenylephrine and its ethyl analog etilefrine via chemical and bio-synthesis. RESULTS: Both sulfates were obtained in higher yield and purity through chemical syntheses compared to biosynthesis. DISCUSSION: A facile method for the production of phenylephrine 3-O-sulfate and etilefrine 3-O-sulfate was established. These compounds will be useful in the development of analytical assays for studying the pharmacokinetics of phenylephrine and its main route of metabolism in the presence of formulation changes and pharmacogenetic variation.

Direct detection of phenylephrine 3-O-sulfate in LS180 human intestinal cells using a novel hydrophilic interaction liquid chromatography (HILIC) assay.

The efficacy of phenylephrine (PE) is controversial due to its extensive pre-systemic metabolism through sulfation to form phenylephrine-3-O-sulfate (PES). Hence quantitation of PES is important in order to study the metabolism of PE. There are no published methods available for direction detection of PES. We have developed and validated a hydrophilic interaction liquid chromatography (HILIC) method for the direct detection of PES and simultaneous detection of PE to study the enzyme kinetics and metabolism of PE to enable approaches to reduce the presystemic metabolism of PE. This is the first method which facilitates direct detection of PES and simultaneous detection of PE using a zwitterionic HILIC column with improved sensitivity in a single short run. The observed quantitative ranges of our method for PE and PES were 0.39-200µM and 0.0625-32µM (respectively) with a run time of 6.0min. The method was applied to the determination of PE and PES in LS180 human intestinal cell line, recombinant enzymes and human intestinal cytosol (HIC).

Pseudoephedrine and circadian rhythm interaction on neuromuscular performance.

This study analyzed the effects of pseudoephedrine (PSE) provided at different time of day on neuromuscular performance, side effects, and violation of the current doping cut-off threshold [World Anti-Doping Agency (WADA)]. Nine resistance-trained males carried out bench press and full squat exercises against four incremental loads (25%, 50%, 75%, and 90% one repetition maximum [1RM]), in a randomized, double-blind, cross-over design. Participants ingested either 180 mg of PSE (supra-therapeutic dose) or placebo in the morning (7:00 h; AM(PLAC) and AM(PSE)) and in the afternoon (17:00 h; PM(PLAC) and PM(PSE)). PSE enhanced muscle contraction velocity against 25% and 50% 1RM loads, only when it was ingested in the mornings, and only in the full squat exercise (4.4-8.7%; P < 0.05). PSE ingestion raised urine and plasma PSE concentrations (P < 0.05) regardless of time of day; however, cathine only increased in the urine samples. PSE ingestion resulted in positive tests occurring in 11% of samples, and it rose some adverse side effects such us tachycardia and heart palpitations. Ingestion of a single dose of 180 mg of PSE results in enhanced lower body muscle contraction velocity against low and moderate loads only in the mornings. These mild performance improvements are accompanied by undesirable side effects and an 11% risk of surpassing the doping threshold.

Regional-dependent intestinal permeability and BCS classification: elucidation of pH-related complexity in rats using pseudoephedrine.

Based on its lower Log P value relative to metoprolol, a marker for the low/high-permeability (P(eff)) class boundary, pseudoephedrine was provisionally classified as BCS low-permeability compound. On the other hand, following oral administration, pseudoephedrine fraction dose absorbed (F(abs)) and systemic bioavailability approaches 100%. This represents a challenge to the generally recognized P(eff)-F(abs) correlation. The purpose of this study was to elucidate the underlying mechanisms behind the confusion in pseudoephedrine's BCS classification. Pseudoephedrine's BCS solubility class was determined, and its physicochemical properties and intestinal permeability were thoroughly investigated, both in vitro and in vivo in rats, considering the complexity of the whole of the small intestine. Pseudoephedrine was found to be unequivocally a high-solubility compound. All of the permeability studies revealed similar phenomenon; at any given intestinal segment/pH, the permeability of metoprolol was higher than that of pseudoephedrine, however, as the intestinal region becomes progressively distal, and the pH gradually increases, pseudoephedrine's permeability rises above that of metoprolol in the former segment. This unique permeability pattern likely explains pseudoephedrine's complete absorption. In conclusion, pseudoephedrine is a BCS Class I compound; no discrepancy between P(eff) and F(abs) is involved in its absorption. Rather, it reflects the complexity behind P(eff) when considering the whole of the intestine. We propose to allow high-permeability classification to drugs with P(eff) that matches/exceeds the low/high class benchmark anywhere throughout the intestinal tract and not restricted necessarily to the jejunum.

The investigation of the interaction between Oxymetazoline hydrochloride and mucin by spectroscopic approaches.

The fluorescence and ultraviolet spectroscopy were explored to study the interaction between Oxymetazoline hydrochloride (OMZH) and mucin under imitated physiological condition. The results demonstrated that the fluorescence quenching mechanism between OMZH and mucin is a combined quenching process. The binding constants (K(a)), binding sites (n) and the corresponding thermodynamic parameters (ΔG, ΔH, and ΔS) of the interaction system were calculated at different temperatures. The hydrogen bonds and van der Waals forces play a major role in the interaction between OMZH and mucin. According to Förster non-radiation energy transfer theory, the binding distance between OMZH and mucin was calculated.

A systematic review of methamphetamine precursor regulations.

AIMS: To assess the effectiveness of methamphetamine precursor regulations in reducing illicit methamphetamine supply and use. METHODS: A systematic review of 12 databases was used to identify studies that had evaluated the impact of methamphetamine precursor regulations on methamphetamine supply and/or use. The guidelines of the Effective Practice and Organization of Care Group (EPOC) of The Cochrane Collaboration were used to determine which study designs were included and assess their quality. RESULTS: Ten studies met the inclusion criteria. These studies evaluated 15 interventions (13 regulations and two related interdiction efforts), all of which were located in North America. Interventions had consistent impacts across various indicators of methamphetamine supply and use. Seven of the 15 interventions produced reductions in methamphetamine indicators (ranging from 12% to 77%). Two of the largest impacts were seen following interdiction efforts, involving the closure of rogue pharmaceutical companies. There was no evidence of a shift into other types of drug use, or injecting use, although the impact on the synthetic drug market was not examined. Null effects were related largely to the existence of alternative sources of precursor chemicals or the availability of imported methamphetamine. CONCLUSIONS: Methamphetamine precursor regulations can reduce indicators of methamphetamine supply and use. Further research is needed to determine whether regulations can be effective outside North America, particularly in developing countries, and what impact they have on the broader synthetic drug market. Improved data on precursor diversion are needed to facilitate the evaluation of precursor regulations.

Identification and characterization of oxymetazoline glucuronidation in human liver microsomes: evidence for the involvement of UGT1A9.

The incubation of oxymetazoline, a nonprescription nasal decongestant, with human liver microsomes (HLMs) supplemented with uridine-5-diphosphoglucuronic acid (UDPGA) generated glucuronide metabolite as observed by LC/MS/MS. The uridine glucuronosyltransferases (UGTs) responsible for the O-glucuronidation of oxymetazoline remain thus far unidentified. The glucuronide formed in HLMs was identified by LC/MS/MS and characterized by one- and two-dimensional NMR to be the ß-O-glucuronide of oxymetazoline. UGT screening with expressed UGTs identified UGT1A9 as the single UGT isoform catalyzing O-glucuronidation of oxymetazoline. Oxymetazoline O-glucuronidation by using HLMs was best fitted to the allosteric sigmoidal model. The derived S(50) and V(max) values were 2.42 ± 0.40 mM and 8.69 ± 0.58 pmole/(min mg of protein), respectively, and maximum clearance (CL(max)) was 3.61 L/min/mg. Oxymetazoline O-glucuronidation by using expressed UGT1A9 was best fitted to the substrate inhibition model. The derived K(m) and V(max) values were 2.53 ± 1.03 mM and 54.18 ± 16.92 pmole/(min mg of protein), respectively, and intrinsic clearance (CL(int)) was 21.41 L/(min mg). Our studies indicate that oxymetazoline is not glucuronidated at its nanomolar intranasal dose and thus is eliminated unchanged, because UGT1A9 would only contribute to its elimination at the toxic plasma concentrations.

The stability of oxymetazoline hydrochloride in aqueous solution.

The kinetics of the hydrolysis reaction of oxymetazoline hydrochloride in aqueous solution at three temperatures (343 K, 353 K, 363 K), over the pH-range 0.5-12.5 and ionic strength 0.5 has been investigated. The changes of concentration of oxymetazoline hydrochloride were followed by the HPLC method with UV detection. In the pH range from 0.45 to 12.50, the hydrolysis of oxymetazoline consists of hydrolysis of oxymetazoline molecules catalyzed by hydrogen ions, spontaneous hydrolysis of the dissociated and undissociated oxymetazoline molecules. A minimal rate of the hydrolysis oxymetazoline was observed to occur in the pH range from 2.0 to 5.0. Thermodynamic parameters of the reaction: energy, entropy and enthalpy of activation and the frequency factor for the specific rate constants were determined.

Formaldehyde production promoted by rat nasal cytochrome P-450-dependent monooxygenases with nasal decongestants, essences, solvents, air pollutants, nicotine, and cocaine as substrates.

To identify compounds which might be metabolized to formaldehyde in the nasal cavity, 32 potential substrates for cytochrome P-450-dependent monooxygenases were screened with rat nasal and, for comparison, liver microsomes. Tested substrates included 6 nasal decongestants, cocaine, nicotine, 9 essences, 3 potential air pollutants, and 12 solvents. Each test substrate, with the possible exception of the air pollutants, contained one or more N-methyl, O-methyl, or S-methyl groups. Eighteen of the tested materials were metabolized to produce formaldehyde by nasal microsomes. Five substrates, namely, the solvents HMPA and dimethylaniline, cocaine, and the essences dimethyl anthranilate and p-methoxyacetophenone, were metabolized to produce formaldehyde at rates exceeding 1000 pmol/mg microsomal protein/min by nasal microsomes. Eight substrates, including four nasal decongestants, nicotine, and an extract of diesel exhaust particles, were metabolized to produce formaldehyde at rates of 200 to 1000 pmol/mg microsomal protein/min. Five other substrates were metabolized to formaldehyde at detectable rates. The results indicate that a variety of materials which often come in contact with the nasal mucosa can be metabolized to formaldehyde by nasal enzymes. The released formaldehyde may influence the irritancy of inhaled compounds and has been suggested to play a role in the tumorigenicity of some compounds.

The effects of nasal drops and their additives on human nasal mucociliary clearance.

A method for measurement of nasal mucociliary clearance in vivo is described. A drop, containing saccharine sodium and indigo carmine is placed on the edge of the ciliary epithelium in the entrance to the nose. The time between placement and the sensing of the sweet taste as well as the appearance of a blue line in the nasopharyngeal cavity is measured and called the transport time. Two preservatives, two nasal drops and one viscosity-increasing substance have been investigated and the results are compared with their effects on the ciliary beat frequency of chicken embryo tracheas in vitro. The more the transport time is increased by a compound the more the ciliary beat frequency is decreased. Chlorbutol 0.5% increases transport time more and decreases ciliary beat frequency more than benzalkonium chloride 0.006% + EDTA 0.1%. Otrivin 0.1% increases transport time more and decreases ciliary beat frequency more than Rhinoguttae xylometazolini 0.1% (F.N.A.). These results support those obtained with the photo-electric registration device applicated on chicken embryo tracheas and human adenoids as described in earlier publications.

[On the absorption of decongestive nose-drops-investigation with a radioactive labelled imidazoline-derivate (author's transl)]. / Zur Resorption abschwellender Nasentropfen

In animal experiments, the absorption of a nasal decongestive substance after application to the nasal mucosa was studied. After an exposition-time of 60 minutes, about 1% of the substance applied could be measured in the total blood volume. An incorporation of the substance into proteins of the nasal mucosa could not be found. By means of frozen-section-autoradiography, the way of the applied decongestive substance through the mucosa could be investigated. The reasons for the relative small absorption rate are discussed. The chemical structure and the vasoconstrictory effect probably are reliable for that.