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Biomedical subjects

F Jane

Publications and source records attributed to F Jane.

16 recordsLinked to original sources
PubMed1995

A pharmacokinetic-pharmacodynamic linking model for the alpha 2-adrenergic antagonism of idazoxan on clonidine-induced mydriasis in the rat.

The relationship between concentration and inhibitory effect of the alpha 2-adrenoceptor antagonist idazoxan on clonidine-induced mydriasis has been studied in the rat using pharmacokinetic-pharmacodynamic simultaneous modelling. Fifteen minutes after the anaesthesia of rats with sodium pentobarbitone (55 mg kg-1, i.p.), and 5 min after the administration of clonidine (0.3 mg kg-1, i.v.) to rats pretreated with idazoxan (3 mg kg-1, i.v., and 3 and 10 mg kg-1, orally) at different time intervals, pupil diameters were assessed. The pharmacokinetics of idazoxan were adequately described by a monoexponential equation. Using a pharmacokinetic-pharmaco-dynamic linking model, the concentration-effect relationships of idazoxan were derived, and were quantified by the inhibitory simple Emax model. At the effect compartment, the estimated apparent IC50 was 153.6 ng mL-1. Values of clearance, volume of distribution and elimination half-life were 71.2 mL kg-1 min-1, 3134 mL kg-1 and 30.5 min, respectively. These results could contribute to better characterization of the pharmacodynamic and toxicological profiles of idazoxan in experimental models in which a different pharmacokinetic behaviour of the drug is presumed.

Administration, Oral↗
PubMed1991

High-performance liquid chromatographic separation of caffeine, theophylline, theobromine and paraxanthine in rat brain and serum.

Caffeine and its metabolites theophylline, theobromine and paraxanthine have been determined in rat brain and serum samples by high-performance liquid chromatography with ultraviolet detection. The recovery, 85-103%, allowed quantification by external standard methods. The variability was found to be less than 3 and 7% for intra-day and inter-day assays, respectively. The detection limit, 1.57 ng of methylxanthines on column, allowed the determination of 62.5 ng/g or ml in biological material. Rats treated with 30 mg/kg caffeine (subcutaneously) were sacrificed at different times (1, 6, 12 and 24 h). Higher concentrations of methylxanthines (specially paraxanthine) were observed in the striatum than in the rest of the brain, and it was also observed that the clearance of methylxanthines was faster in serum than in brain structures.

Animals↗
PubMed1991

Changes in gentamicin pharmacokinetic profiles induced by mechanical ventilation.

The influence of controlled mechanical ventilation (CMV) on the pharmacokinetic profile of gentamicin has been examined in 23 patients after elective open heart surgery. A parallel design was adopted in two groups of patients; 13 patients requiring CMV for at least 32 h after surgery, all of whom were able to breath spontaneously (SB) after 72 h (study group), and 10 patients who required CMV for only a brief period and who showed SB at 32 h postsurgery. Haemodynamic parameters remained stable throughout the study. Apparent volume of distribution (VZ), half-life (t1/2), total clearance (CL), peak (Cmax") and trough (Cmin") plasma levels at steady-state for target levels (6-8 microgram/ml), were measured. In the study group significant differences between CMV and SB conditions were found in VZ (mean 0.36 and 0.25 l/kg). t1/2 (mean 3.63 and 2.90 h) and Cmax" (mean 4.30 and 5.53 microgram/ml) while Cmin" (mean 1.06 microgram.ml-1 and 0.92 microgram.ml-1) did not change significantly. In contrast, the pharmacokinetics in the control group showed no differences. It appears that CMV leads to an increase in gentamicin Vz which accounts for the fall in Cmax" below the therapeutic dose range (less than 5 microgram/ml) recommended for gentamicin. It seems advisable to use a large dose of gentamicin in patients receiving CMV, even before the level is assessed.

Adult↗
PubMed1990

Is experimental catalepsy properly measured?

Following logarithmic transformation (ln) of total duration of haloperidol-induced catalepsy in the rat, measured by means of the bar test, a normalization of the results is achieved. With the help of this transformation we have been able to study what are probably the most important variables involved in the measuring of experimental catalepsy and to establish some criteria for a better use of such measures: 1) repeated measures of catalepsy have to be taken in order to avoid the stress-induced inhibition of catalepsy caused by the new experimental situation, 2) the dose of neuroleptic used has to be sufficiently low to permit the measurement of total or real duration of catalepsy between two determinations, and 3) the dose of neuroleptic has to be sufficiently high to prevent the development of a learned "pseudocatalepsy."

Adrenal Glands↗
PubMed1990

Effects of long-term treatment with metoprolol and hydrochlorothiazide on plasma lipids and lipoproteins.

In order to evaluate the effects of one-year antihypertensive treatment on plasma lipids and lipoproteins, 65 patients whose diastolic blood pressure was in the range 95-120 mmHg were randomly allocated to groups that received either hydrochlorothiazide or metoprolol, or both drugs when the response to one of them was insufficient to control blood pressure. Blood pressure was effectively reduced in all groups. Patients on hydrochlorothiazide showed a significant increase (P less than 0.01) in low-density lipoprotein cholesterol (LDL-C) after 3 months of treatment. A significant increase in triglycerides was observed after 6 and 12 months, together with a decrease in high-density lipoprotein cholesterol (HDL-C) after 12 months (P less than 0.05) of treatment in patients on metoprolol. In patients treated with both hydrochlorothiazide and metoprolol, total cholesterol increased after 3 (P less than 0.001) and 6 months (P less than 0.05), triglycerides increased after 6 (P less than 0.01) and 12 months (P less than 0.01), and LDL-C increased after 3 (P less than 0.05), 6 (P less than 0.001) and 12 months (P less than 0.01) of treatment, respectively. In 61% of the patients, three or more lipid parameters were affected during the study period. We conclude that long-term antihypertensive treatment with hydrochlorothiazide, metoprolol, and particularly with both drugs, can induce lipid effects that deserve recognition, because in some cases these might counteract the possible benefit of a reduction in blood pressure on the prevention of coronary heart disease.

Cholesterol↗
PubMed1989

Pharmacodynamic effects of a single 10-mg dose of the angiotensin converting enzyme inhibitor ramipril in patients with impaired renal function.

A single oral 10-mg dose of ramipril, a long-acting angiotensin converting enzyme (ACE) inhibitor, was given to 24 hypertensive patients with different degrees of renal function. Creatinine clearance ranged from below 15 ml/min (n = 9) to above 80 ml/min (n = 3). Serial blood samples were taken for the determination of ACE activity, plasma renin activity (PRA), aldosterone (ALDO), angiotensin II (AT II), and serum creatinine (CR). Blood pressure was also monitored before and after medication. After administration of ramipril systolic and diastolic blood pressure (BP) fell; the decreases were unrelated to renal function. Peak BP-lowering effect was seen at 6 h basal, 174 +/- 19.5/102.6 +/- 8.9 to 149.8 +/- 19.7/87.6 +/- 13.3 mm Hg (mean +/- SD; p less than 0.001). ACE inhibition occurred within 2 h, being maximal at 4 h: basal, 82.6 +/- 17.9 to 0.2 +/- 0.6 nmol/ml/min (p less than 0.001). The greater the renal impairment, the longer the ACE inhibition. Angiotensin II was reduced maximally at 10 h after dosing, from 10.4 +/- 5.4 to 6.2 +/- 3.6 pg/ml (p less than 0.01). Aldosterone also fell from 212 +/- 188.4 to 134 +/- 73.3 pg/ml at 6 h (p less than 0.01). Plasma creatinine was unchanged: 401.3 +/- 315.7 to 394.9 +/- 306.1 nmol/L (NS). Ramipril, given as a single oral dose, lowers BP in hypertensives with both normal and impaired renal function, inhibits ACE activity, and causes no change in serum creatinine.

Adult↗
PubMed1988

Theophylline reverses haloperidol-induced catalepsy in the rat. Possible relevance to the pharmacological treatment of psychosis.

The effect of theophylline (5, 15, or 30 mg/kg sc) on the catalepsy induced by haloperidol in the rat was studied. Theophylline was shown to induce a dose-dependent inhibition of this catalepsy. These data support the hypothesis that the methylxanthines are dopamine agonists and suggest that coffee, tea, and cola drinks should be avoided by patients undergoing neuroleptic treatment.

Animals↗
PubMed1988

Conditioning of rotational behavior after the administration of a single dose of apomorphine in rats with unilateral denervation of the dopaminergic nigrostriatal pathway: relevance to drug addiction.

Our aim is to study the relationship of drug activation of the dopamine neurotransmission system and the conditioning of environmental stimuli present at the time of drug administration. We injected a single dose of apomorphine (0.05 mg/kg SC) in rats with the nigrostriatal dopamine pathways unilaterally denervated with 6-hydroxydopamine, which generates rotational behavior contralateral to the lesioned hemisphere. We observed rotational behavior without apomorphine administration when animals were reexposed at different time intervals to the same environment in which they performed turning behavior. The present findings show that this rotational behavior can be conditioned to environmental stimuli in a strong and long-lasting way. In light of the relationship between opioids and the dopaminergic system, similar conditioning could take place in the learning processes implicated in drug addiction.

Animals↗
PubMed1988

Microsomal effects of cyproterone acetate and flutamide in rat testis.

1. Effects of two doses of cyproterone acetate (CA) and flutamide (FLU) (50 and 100 mg/kg/3 days) on the testicular steroidogenesis in male rats have been investigated, by measuring the content of cytochrome P-450, cytochrome b5 and cytochrome c reductase activity in the microsomal fraction. 2. CA provoked a significant decrease in cytochrome P-450 content while FLU induced an increase with the lowest dose but a significant decrease after administration of 100 mg/kg. 3. On the other hand, in all cases the cytochrome b5 and cytochrome c reductase activity remained unchanged. 4. The plasma levels of LH and testosterone were measured after CA and FLU injection (50 and 100 mg/kg/3 days). 5. CA administration provoked a reduction in blood levels of these hormones while FLU induced a significant increase in both. 6. These data suggested that CA and FLU modified the cytochrome P-450 in rat testes by an indirect mechanism, probably through the modification of LH plasma levels.

Androgen Antagonists↗
PubMed1988

Pharmacokinetics of fosfosal after single and multiple oral doses in man.

Fosfosal is a new salicylic acid derivative used in analgesic and anti-inflammatory therapy. In this study, pharmacokinetic evaluation of fosfosal after a single 2,400 mg and three different oral dose schedules (1,200 mg t.i.d., 2,400 mg b.i.d. and 2,400 mg t.i.d.) was carried out, in six healthy male volunteers, to assess which doses provide steady state plasma concentrations within the therapeutic range (150-300 micrograms/ml). Plasma concentrations of both fosfosal and its active metabolite, salicylic acid, were determined by means of an HPLC method. For the 2,400 mg t.i.d., Cmin-ss and Cmax-ss values were 184 micrograms/ml and 276 micrograms/ml, respectively, being significantly higher (p less than 0.02) than with the other regimes and, unlike the latter, falling within the anti-inflammatory therapeutic range. In addition, the 2,400 mg t.i.d. showed a significant prolongation (p less than 0.005) of salicylic acid t1/2, as well as a higher AUC-ss 0-8 h dosing interval compared to the other multidose schedules and to the AUC0-infinity for the single dose. As expected, both facts reflect that the highest daily dose of fosfosal has a nonlinear concentration-dependent elimination rate.

Administration, Oral↗
PubMed1987

L-dopa causes an acute, partial and reversible reversal of denervation-induced supersensitivity of striatal dopaminergic receptors.

Denervation-induced supersensitivity of the striatal dopamine receptors can be quantified by the turning behaviour induced by apomorphine. With this experimental model we found that high-dose L-dopa/carbidopa administration reduced this supersensitivity. This effect was seen on the 1st day and did not alter over 5 or 10 days of treatment, but disappeared when medication was discontinued. The degree of reduction was the same, independent of the dose and period of administration. This effect could provide a useful model for studying the phenomenon of the irreversibility of the supersensitivity of the striatal dopamine receptors.

Animals↗
PubMed1985

Effects of bromocriptine on catecholamine receptors mediating cardiovascular responses in the pithed rat.

The interaction of bromocriptine with several catecholamine receptors that control the sympathetic responses at cardiac and vascular level has been studied in pithed adrenalectomized and vagotomized normotensive rats. Bromocriptine (30 and 100 micrograms/kg) inhibited the stimulation-induced pressor responses in the pithed rat without modifying the pressor responses induced by noradrenaline. Sulpiride (0.3 mg/kg) abolished the effects of bromocriptine (30 micrograms/kg) but only partially prevented the effects of bromocriptine (100 micrograms/kg) on the stimulation-induced pressor responses. Yohimbine (0.3 mg/kg) partially antagonised the inhibitory effect of bromocriptine on stimulation-induced pressor responses. Combination of yohimbine and sulpiride abolished attenuation of the stimulation-induced pressor responses by bromocriptine (100 micrograms/kg). Bromocriptine (0.3 and 1 mg/kg) shifted to the right the frequency-response curve of increases in heart rate. This effect was prevented by yohimbine (0.3 mg/kg) but not by sulpiride (0.3 mg/kg). The same doses of bromocriptine were ineffective on heart rate increases induced by noradrenaline. Bromocriptine (0.3 and 1 mg/kg) shifted to the right the increases in diastolic blood pressure induced by methoxamine without modifying those induced by xylazine and noradrenaline. These results suggest that bromocriptine acts on the peripheral sympathetic nervous system of the pithed rat as an agonist of presynaptic dopamine receptors and alpha 2-adrenoreceptors and as an antagonist of postsynaptic alpha 1-adrenoreceptors.

Animals↗
PubMedDate not supplied

Theophylline pharmacokinetics following single and repeated administration of slow-release capsules.

The aim of this study was to evaluate the pharmacokinetic profile after single and multidose oral administration of a new slow-release theophylline formulation and the bioavailability at steady-state during two dosing intervals (5th and 8th day) in 6 healthy subjects. A dose of 6 mg/Kg (capsules) was given for the single and at fixed 12 h intervals during 10 days for the multidose schedule. Theophylline kinetics were best described by a one-compartment open model. After single dose the elimination half-life was 7.22 +/- 2.36 h, the Vd area/F was 0.50 +/- 0.07 l/kg and the total clearance/F was 0.86 +/- 0.24 ml/Kg/min, which was similar to results reported in other studies. Steady-state plasma levels were predictable from the kinetic data and were reached between the 4th and 6th dose, falling within the therapeutic range throughout the dosing interval. The percentage of fluctuation remained constant during both intervals, around 33 and 35% respectively. Bioavailability parameter values for the two intervals showed no differences either in extent or in rate. A circadian rythm was confirmed with the mean morning trough values significantly greater than the corresponding mean evening values. From these results it may be concluded that the formulation studied produces few fluctuations of theophylline levels during the 12 h interval between both administrations, thus permitting a good therapeutic cover in chronic therapy.

Adult↗