Novel liquid chromatographic assay for the low-level determination of apomorphine in plasma.
A novel HPLC assay which is rapid, reproducible and sensitive has been developed for the analysis of apomorphine in plasma. The assay incorporates boldine as an internal standard, and uses solid-phase extraction on C18 mini-columns for sample clean-up and concentration, so enabling quantitation of apomorphine at 500 pg/ml using fluorescence detection (lambda(ex) 270 nm, lambda(em) 450 nm). The HPLC assay comprised a 25 cm-long Techopak C18 column and a mobile phase of (0.25 M sodium dihydrogen phosphate plus 0.25% heptane sulphonic acid, to pH 3.3 with orthophosphoric acid) containing 30% (v/v) methanol and 0.003% (w/v) EDTA, run at a flow-rate of 1.5 ml/min. Calibration plots prepared in plasma were linear over the range 1-30 ng/ml, (limit of quantitation (LOQ) = 490 pg/ml) with R.S.D. of 0.05% and R.E. of 5.0% at the level of 1 ng/ml. Preliminary pharmacokinetic data from two patients given apomorphine by 12 h subcutaneous infusion (patient A dose = 35 mg and patient B dose = 141 mg) showed apomorphine elimination from plasma to fit a two-compartment model, with initial half-lives of 8.2 and 46.6 min, elimination half-lives of 76.4 and 166.5 min and area under the plasma concentration-time curve (AUC) values of 236 and 405 ng h/ml, respectively.
Priston
M J
MJ
Pharmacy Department, Royal Devon and Exeter Hospital, UK.
Sewell
G J
GJ
D000975:Antioxidants / Q000032:analysis; D001058:Apomorphine / Q000097:blood* / Q000737:chemistry / Q000493:pharmacokinetics; D001060:Aporphines / Q000032:analysis; D019540:Area Under Curve; D002138:Calibration; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D018491:Dopamine Agonists / Q000097:blood* / Q000737:chemistry / Q000493:pharmacokinetics; D004355:Drug Stability; D006207:Half-Life; D006801:Humans; D016014:Linear Models; D008623:Mercaptoethanol / Q000737:chemistry; D012015:Reference Standards; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013050:Spectrometry, Fluorescence; D013696:Temperature; D013997:Time Factors
D000975:Antioxidants; D001060:Aporphines; D018491:Dopamine Agonists; D008623:Mercaptoethanol; C011686:boldine; D001058:Apomorphine