Determination of bromocriptine in plasma: comparison of gas chromatography, mass fragmentography and liquid chromatography

Gas chromatographic, mass fragmentographic and liquid chromatographic techniques for the determinations of bromocriptine (2-bromo-alpha-ergocriptine; Parlodel) in human plasma are described. These methods were found to be suitable for determining concentrations of bromocriptine down to 0.5, 1.0 and 10.0 microgram/l, respectively. Accuracy, specificity and analytical capacity were satisfactory for all three methods. Gas chromatography was compared with liquid chromatography, and the two methods were demonstrated to give identical results in patients treated with bromocriptine for Parkinson's disease. Gas chromatography was also compared with mass fragmentography, and the results from these two assays were also in agreement.

Plasma cortisol in the horse, diurnal rhythm and effects of exogenous ACTH

Peripheral blood plasma Cortisol concentration and its diurnal variation was measured in 4 horses. Mean concentration of Cortisol during 24 hrs. was 42 ng/ml (s ± 20 ng/ml). Peak values occurred at 6 a.m. and the lowest values were observed at about 6 p.m. (mean 65 ng/ml and 20 ng/ml, respectively).

Long-acting ACTH at a dose of 150 i.u. was given by intramuscular injection to the 4 horses. Peak Cortisol concentrations markedly exceeding the prestimulation level were obtained between 2 and 4 hrs. after injection. During the immediate 24 hrs. after these peaks, the mean Cortisol level was markedly lower and the cyclic variation out of phase with the basal diurnal pattern. After a gradual adjustment during the second postinjection day, no differences could be seen between the 2 patterns on day 3 after injection.

Neurometabolic and behavioural effects of haloperidol in relation to drug levels in serum and brain

A method has been developed for the quantitative determination of haloperidol in brain and other tissues. Such determinations have been made after acute and chronic administration of haloperidol to Sprague-Dawley rats. Different regions of the brain including the striatum, the limbic forebrain and the cerebellum have been analyzed separately. The haloperidol effects on Dopa formation have been studied in the same tissue samples. The stimulation of prolactin secretion via blockade of hypothalamic dopaminergic mechanisms and behavioural effects of the drug have been evaluated in parallel experiments. The elimination of haloperidol from brain tissue is a multiphasic process. The fourth phase of elimination is the slowest with a half life of 4 days. No strict correlation was found between serum and brain concentrations of haloperidol. Both after acute and chronic administration there exists apparently a saturating dose above which the brain concentration of the drug increases very little. The dose seems to coincide with that beyond which little increase in Dopa formation is observed. A pharmacokinetic analysis suggests an element of saturable binding or transfer of haloperidol to brain tissue. This mechanism is not preferentially localized to areas of brain rich in dopaminergic synapses. A good correlation was found between the haloperidol concentration in the brain on the one hand and its effects on behaviour, on serum prolactin values and on Dopa formation on the other.