A rapid high-pressure liquid chromatographic procedure for determination of flumazenil in plasma

INTRODUCTION

Flumazenil antagonizes the effects of benzodiazepines at gamma-aminobutyric acid (GABA) type A receptors in the central nervous system. Flumazenil has been reported to provoke panic attacks in patients with panic disorder (PD) but not in healthy controls. A rapid high-pressure liquid chromatographic (HPLC) method was developed for determination of flumazenil in plasma samples from PD patients receiving flumazenil and the results obtained with that assay are reported here.

METHODS

Samples from 37 PD subjects receiving 2 mg of flumazenil intravenously were analyzed. Extraction under basic conditions was followed by an HPLC assay with UV detection (250 nm). Lamotrigine was used as intermal standard and a standard curve was constructed for each assay run. Flumazenil concentrations were measured in all the subjects in samples collected at 2 and 4 min after the drug administration and in some subjects, measurements were also done in samples collected at 7.5, 15, 30, 45, and 60 min.

RESULTS

The procedure was reproducible and linear (from 2.5 to 1000 ng/ml). At 2 and 4 min after flumazenil administration, the concentrations did not differ significantly between panicking and nonpanicking subjects, indicating that the pharmacokinetics of the drug is not the major determinant of the responses. There was a steep decline in the plasma concentration-time profile during the first 4 min, reflecting an extensive and rapid distribution after which the decline was slower.

DISCUSSION

The method described here is rapid, replicable, and convenient for the determination of flumazenil in plasma.

Response to pentagastrin after acute phenylalanine and tyrosine depletion in healthy men: a pilot study

OBJECTIVE

To assess the effects of the acute depletion of the catecholamine precursors phenylalanine and tyrosine on mood and pentagastrin-induced anxiety.

DESIGN

Randomized, double-blind controlled multiple crossover study.

SETTING

University department of psychiatry.

PARTICIPANTS

6 healthy male volunteers.

INTERVENTIONS

3 treatments were compared: pretreatment with a nutritionally balanced amino acid mixture, followed 5 hours later by a bolus injection of normal saline placebo; pretreatment with a balanced amino acid mixture, followed by a bolus injection of pentagastrin (0.6 microgram/kg); and pretreatment with an amino acid mixture without the catecholamine precursors phenylalanine or tyrosine, followed by pentagastrin (0.6 microgram/kg).

OUTCOME MEASURES

Scores on the panic symptom scale, a visual analogue scale for anxiety, the Borg scale of respiratory exertion and the Profile of Mood States Elation-Depression Scale.

RESULTS

Pentagastrin produced the expected increases in anxiety symptoms, but there was no significant or discernible influence of acute phenylalanine and tyrosine depletion on anxiety or mood.

CONCLUSIONS

These pilot data do not support further study using the same design in healthy men. Under these study conditions, phenylalanine and tyrosine depletion may have larger effects on dopamine than noradrenaline. Alternative protocols to assess the role of catecholamines in mood and anxiety are proposed.