A method for determining 4-aminopyridine in plasma: pharmacokinetics in anaesthetized guinea pigs after intravenous administration.
An HPLC assay has been developed to measure 4-aminopyridine (4-AP) in guinea pig plasma. For the assay, all plasma samples (50 microL) were microfiltered following the addition of an internal standard (3,4-diaminopyridine). Filtrates (10 microL) were directly injected into a spherical silica column (100 x 2.1 mm; 5 microns); detection was achieved at 266 nm. Standard curves had correlation coefficients ranging from 0.9923 to 0.9992 and coefficients of variation expressed as a percentage (% CV) of below 8%. Precision was expressed as between-day and within-day variability of five test sample concentrations. Between-day % CV ranged from 4.0 to 6.5%. Within-day % CV ranged from 3.6 to 6.9%. Accuracy was assessed by examining expected within-day test sample concentrations against calculated concentrations; per cent errors were all below 10%. Stability studies demonstrated % CV below 5% after repeated freezing. The method was employed to study the pharmacokinetics of 4-AP after intravenous administration to anaesthetized guinea pigs. Serial blood samples (150 microL) were collected at predetermined time intervals up to 4 h post-4-AP (2 mg/kg, i.v.) administration. 4-AP demonstrated a biexponential decline in the plasma-concentration curve as a function of time indicating a two compartment model for this drug. Selected mean pharmacokinetic parameter estimates were alpha-half-life, 0.37 min; beta-half-life (biological half-life) for terminal slope, 109 min; and volume of distribution at steady state, 1036.18 mL/kg. 4-AP was found to rapidly and extensively partition into a peripheral tissue compartment and demonstrated a relatively long biological half-life. The findings from the current pharmacokinetic experiments support the pharmacology of 4-AP in its role for reversing saxitoxin (STX)- and tetrodotoxin (TTX)-induced diaphragmatic failure in terms of onset of action and duration of effect in anaesthetized guinea pigs.
Capacio
B R
BR
US Army Medical Research Institute of Chemical Defense, Aberdeen Proving Ground, Maryland 21010-5425, USA.
Byers
C E
CE
Matthews
R L
RL
Chang
F C
FC
D015761:4-Aminopyridine / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics*; D000758:Anesthesia; D000818:Animals; D002339:Carotid Arteries / Q000601:surgery; D002406:Catheterization, Peripheral; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D004355:Drug Stability; D005615:Freezing; D006168:Guinea Pigs; D006207:Half-Life; D007275:Injections, Intravenous; D007601:Jugular Veins / Q000601:surgery; D008297:Male; D013997:Time Factors; D014520:Urethane
D014520:Urethane; D015761:4-Aminopyridine