Steady-state bioavailability of dexbrompheniramine and pseudoephedrine from a repeat-action combination tablet

Quantification of pseudoephedrine in human plasma by LC-MS/MS using mosapride as internal standard

A simple, sensitive and rapid high-performance liquid chromatography/positive ion electrospray tandem mass spectrometry (LC-MS/MS) method was developed and validated for the quantification of pseudoephedrine in human plasma using mosapride as internal standard. Following solid-phase extraction, the analytes were separated using an isocratic mobile phase on a reverse-phase column and analyzed by MS/MS in the multiple-reaction monitoring mode using the respective [M + H](+) ions, m/z 166/148 for pseuoephedrine and m/z 422/198 for the IS. The method exhibited a linear dynamic range of 2-1000 ng/mL pseudoephedrine in human plasma. The lower limit of quantification was 2 ng/mL with a relative standard deviation of less than 9% for pseudoephedrine. Acceptable precision and accuracy were obtained for concentrations over the standard curve range. The total chromatographic run time of 2 min for each sample made it possible to analyze more than 400 human plasma samples per day. The validated method has been successfully used to analyze human plasma samples for application in pharmacokinetic, bioavailability or bioequivalence studies.

Simultaneous quantification of fexofenadine and pseudoephedrine in human plasma by liquid chromatography/tandem mass spectrometry with electrospray ionization: method development, validation and application to a clinical study

To support the pharmacokinetic and bioavailability study of a once-daily fexofenadine/pseudoephedrine combination, a high-performance liquid chromatography/positive ion electrospray tandem mass spectrometry (HPLC/ESI-MS/MS) method for the simultaneous quantification of fexofenadine and pseudoephedrine was developed and validated with 500 microL human plasma using mosapride as an internal standard (IS). Following solid-phase extraction, the analytes were separated using an isocratic mobile phase on a reversed-phase column and analyzed by MS/MS in the multiple reaction monitoring mode using the respective [M+H]+ ions, m/z 502/466 for fexofenadine, m/z 166/148 for pseuoephedrine and m/z 422/198 for the IS. The method exhibited linear dynamic ranges of 1-500 ng/mL and 2-1000 ng/mL for fexofenadine and pseudoephedrine, respectively, in human plasma. The lower limits of quantification were 1 and 2 ng/mL with a relative standard deviation of less than 10% for fexofenadine and pseudoephedrine, respectively. Acceptable precision and accuracy were obtained for concentrations over the standard curve range. The total chromatographic run time was 2 min and more than 400 human plasma samples could be analyzed in one day by running the system overnight. The method is precise and sensitive enough for its intended purpose.

Direct injection of plasma to determine pseudoephedrine by high performance liquid chromatography with column switching

An HPLC method has been developed for the determination of pseudoephedrine in plasma using column switching. Preparation of the sample was simple in that only 1000 microL of water was added to 200 microL of plasma before injection. A 900 microL aliquot was injected onto the precolumn. Double distilled water was used to elute and remove proteins and polar components in the sample. The components retained on the precolumn were flushed forward onto the analytical column by the mobile phase (acetonitrile-0.2 mol/L ammonium sulphate, 10:90 v/v) with automated column switching. The limit of determination of pseudoephedrine in plasma was 12 ng/mL. The relative standard deviations of intra- and inter-assay for the determination of pseudoephedrine in plasma were 1.2-9.8% over the concentration range 1020-21.8 ng/mL. The mean recovery by on-line solid phase extraction was 94.76% (RSD = 1.1%).

Alkylamine antihistamine toxicity and review of Pediatric Toxicology Registry of the National Association of Medical Examiners. Report 4: Alkylamines

Antihistamines are popular nonprescription medications for the treatment of allergy and cold symptoms. Accidental exposures to these preparations are common with > 14,000 occurring annually in children under the age of 6 years (1). Despite this, there is limited information about toxic and lethal concentrations of these drugs in children. We present a case of a pediatric fatality due to a common brompheniramine and phenylpropanolamine preparation and review available Pediatric Toxicology Registry data on alkylamine antihistamines. The data collected by the Pediatric Toxicology Registry on the drug phenylpropanolamine has been previously reported (2). A review of the Registry data suggests that postmortem blood brompheniramine concentrations of 0.4 mg/L and greater in children is indicative of brompheniramine poisoning. However, pheniramine was also present in the blood in the same case and may have caused an additive effect. The data are insufficient to establish the threshold of fatal blood pheniramine concentration in children. Data for chlorpheniramine are lacking.

Non-prescription sympathomimetic agents and hypertension

In recent years, considerable attention has been focused on the pressor effects of nonprescription sympathomimetic agents. The impact and usage of these agents especially ephedrine, pseudoephedrine, phenylpropanolamine and phenylephrine, in hypertensive patients has been the topic of constant debates. The present review is an attempt to report and evaluate all the clinical trials and cases of pressor reactions associated with these 4 agents. The study protocols used in these clinical trials are examined and comments made on any diversion from the standard design. Many factors are found to cause the discrepancies in the data available. It is concluded that ephedrine and phenylpropanolamine are best avoided by hypertensive patients due to higher probability of causing pressor reactions. Data on pseudoephedrine and phenylephrine appear to indicate non-significant effects on blood pressure of normotensive subjects when used at the recommended oral dose as nasal decongestants. Phenylephrine is also commonly employed in nasal and eye drops and the limited data available appear to support its usage in hypertensive patients. However, it is noted that most of the clinical trials involve normotensive subjects and the majority of the results could not be verified due to inadequacies in the study design. This paucity and inconclusive information on hypertensive patients warrants further investigations with emphasis on the study protocols used.