Selective liquid chromatographic assay for propylthiouracil in plasma

Determination of propylthiouracil and methylthiouracil in human serum using high-performance liquid chromatography with chemiluminescence detection

Based on the sensitizing effect of formaldehyde on the chemiluminescence (CL) reaction of propylthiouracil (PTU) and methylthiouracil (MTU) with acidic potassium permanganate and the combination technique of high-performance liquid chromatography (HPLC), a sensitive, selective and simple post-column CL detection method for determining PTU and MTU is described. The optimal conditions for the CL detection and HPLC separation were carried out. The linear ranges were 0.1-20 microg mL(-1) for MTU and 0.1-10 microg mL(-1) for PTU, the detection limits were 0.03 microg mL(-1) for PTU, 0.03 microg mL(-1) for MTU and the quantification limits were 0.1 microg mL(-1) for PTU, 0.1 microg mL(-1) for MTU. The method has been satisfactorily applied for the determination of MTU and PTU in human serum samples.

Methimazole and propylthiouracil equally cross the perfused human term placental lobule

Propylthiouracil (PTU) is widely believed to cross the placenta less freely than methimazole (MMI) and is therefore regarded as the preferred drug for treatment of hyperthyroidism in pregnancy. Clinical studies comparing the two drugs show, however, no differences in maternal or fetal thyroid function. We investigated transfer from the maternal to the fetal circuit in the isolated perfused term human placental lobule of low and high doses of PTU (4 micrograms/mL and 40 micrograms/mL) and MMI (1.5 micrograms/mL and 15 micrograms/mL) in protein-free perfusate and low doses of both drugs with addition of 40 g/L of bovine albumin. Both drugs readily crossed the placenta, reaching equilibrium in all experiments in about 2 h. Drug concentrations in the two circuits fitted a two compartmental model. Transfer kinetics for the two drugs were similar, nonsaturable, and unaffected by addition of albumin. Clearances (mL.min-1.g-1, means +/- SD) of PTU from maternal to fetal circuits were: 0.229 +/- 0.110, 0.216 +/- 0.065, and 0.170 +/- 0.032; and for transfer of MMI: 0.165 +/- 0.025, 0.232 +/- 0.153, and 0.174 +/- 0.009 (for low doses without, low doses with, and high doses without albumin, respectively). Clearances of PTU from fetal to maternal circuits were: 0.147 +/- 0.072, 0.109 +/- 0.014, and 0.116 +/- 0.028; and for transfer of MMI: 0.095 +/- 0.029, 0.122 +/- 0.088, and 0.12 +/- 0.005 (in the same experiments). There was no significant difference between drugs or drug doses and no effect of addition of albumin. We conclude that PTU and MMI have similar placental transfer kinetics.

Kinetic determination of carbimazole, methimazole and propylthiouracil in pharmaceuticals, animal feed and animal livers

Kinetic methods are proposed for the determination of carbimazole(CBZ), methimazole(MMI) and propylthiouracil(PTU) based on their inhibitory effects on the palladium(II)-catalysed reaction between the pyronine G and hypophosphite ions. The reactions are monitored spectrophotometrically at 548 nm. The influence of reaction variables and the interfering effect of other substances were studied. Under the selected experimental conditions (CBZ: 3.6 x 10(-5) mol l-1 pyronine G; pH 3.0; 0.7 microgram ml-1 PdII and 0.2 mol l-1 H2PO2-; MMI: 6 x 10(-5) mol l-1 pyronine G, pH 3.0; 0.7 microgram ml-1 PdII, 0.4 mol l-1 H2PO2-; PTU: 3.6 x 10(-5) mol l-1 pyronine G; pH 3.0; 0.7 microgram ml-1 PdII and 0.3 mol l-1 H2PO2-), these three antithyroids were determined in the following ranges: CBZ, 0.04-0.70 microgram ml-1; MMI, 0.04-0.50 microgram ml-1; PTU 0.08-1.00 microgram ml-1. The methods were applied to the determination of CBZ, MMI and PTU, in pharmaceuticals, animal feed and animal livers.