Human metabolism of phenothiazines to sulfoxides determined by a new high performance liquid chromatography--electrochemical detection method

Phenothiazine-associated apnea in two siblings

A two-month-old white girl presented to our facility with increasing lethargy and new onset apnea and bradycardia following a week of upper respiratory tract infection symptoms. The patient had been receiving a cough syrup containing promethazine hydrochloride during the previous five days, which was temporally correlated with the onset of lethargy and apneic episodes. Upon further investigation, it was discovered that the patient's older sibling also may have experienced phenothiazine-associated apnea after receiving a combination of meperidine hydrochloride, promethazine hydrochloride, and chlorpromazine as a premedication prior to an endoscopic examination. In addition to the presentation of these cases, the literature pertaining to phenothiazine-associated apnea is reviewed.

High-performance liquid chromatography of the antihistamine pyrilamine and its N-oxide using electrochemical detection

The electrochemical behavior of the over-the-counter antihistamine drug pyrilamine and its N-oxide analogue, have been studied by several voltammetric methods. Cyclic voltammograms of pyrilamine maleate in 0.1 M ammonium acetate at pH 7.0 indicated a quasi-reversible electrode process by observing a wave at + 0.85 V and + 1.30 V in the initial anodic sweep followed by a wave at - 1.30 V versus Ag/AgCl. Differential pulse and hydrodynamic voltammetry of pyrilamine and the N-oxide were examined to determine oxidation potentials for use in high-performance liquid chromatography with electrochemical detection (HPLC-ED). Differentiation between pyrilamine and its N-oxide was achieved in HPLC-ED analyses at a detection potential of + 0.7 V and + 0.9 V versus Ag/AgCl with tandem ultraviolet detection at 254 nm. Utility of the HPLC-ED method was demonstrated by the analysis of pyrilamine and the N-oxide in microbial biotransformation samples.

Measurement of blood levels of neuroleptics and metabolites by combined high performance liquid chromatography-radioreceptor assay for D2 and sigma sites

The dopamine (D2) receptor blocking property of antipsychotic medications has been proposed as the mechanism of the therapeutic activity of this class of drugs. This property has also been exploited as a method to quantify therapeutic levels of these drugs in patients. However, the lack of correlation among dosage, blood levels and clinical response has resulted in a contradictory literature on both mechanism and quantification of these drugs. Bioactivity and chemical identity of the commonly prescribed neuroleptic drug fluphenazine and its metabolites in human plasma were determined by a new method which combines the selectivity of chemical methods with the sensitivity and bioassay of the radioreceptor assay (RRA) method. Fluphenazine and its metabolites were separated and identified in human plasma by an ion-pairing reverse phase high performance liquid chromatographic method with electrochemical detection. A volatile buffer system was employed which was compatible with facile sample preparation for post-column analyses, and which provided sharp, symmetrical chromatographic peaks of parent compound and metabolites. Post chromatography, HPLC fractions were assayed by RRA for D2, alpha 1 and sigma receptors. More than one pattern of metabolism of the drug was seen, including biosynthesis of drug metabolites with biological activities at these receptor types. The individual differences with which this occurs may contribute to the variabilities seen in clinical response to neuroleptics, and to difficulties in neuroleptic blood level determinations.