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  • 1
    Electronic Resource
    Electronic Resource
    Plasma concentration of α-methyldopa and sulphate conjugate after oral administration of methyldopa and intravenous administration of methyldopa and methyldopa hydrochloride ethyl ester (1975)
    Springer
    European journal of clinical pharmacology 8 (1975), S. 381-386 
    Details
    ISSN: 1432-1041
    Keywords: α-methyldopa ; plasma concentration ; hypertension ; sulphate conjugation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The plasma concentrations of free α-methyldopa and methyldopa sulphate conjugate were measured in 7 hypertensive patients with normal renal function following α-methyldopa (1 g) orally. Five of these patients subsequently received α-methyldopa ethyl ester (250 mg) (methyldopate) intravenously and two further patients received 250 mg of α-methyldopa intravenously. After oral administration a large amount of total plasma α-methyldopa was present as sulphate conjugate. There were wide interindividual differences in the ratio of free: conjugated α-methyldopa in plasma (ratio at 4 hours ranged from 3.73 – 0.83) suggesting that individual differences in the extent of sulphate conjugation may occur. There was no close correlation between the degree of conjugation and the fall in arterial pressure. At all time intervals examined, plasma concentrations were higher following intravenous α-methyldopa than α-methyldopate. The plasma concentration of α-methyldopa (free and esterified) 60 minutes after i.v. α-methyldopate was 1.7±0.3 µg/ml wile at the same time after the same dose of methyldopa by the same route the mean concentration was 5.9 µg/ml. Although small amounts of sulphate conjugate were detected after i.v. α-methyldopate, insignificant quantities of conjugate were found after i.v. α-methyldopa. The average fall in mean arterial pressure was 27 mm Hg following i.v. α-methyldopa but only 2.7 mm Hg following α-methyldopate. These results suggest that sulphate conjugation of α-methyldopa occurs in the gastrointestinal tract during absorption. Hydrolysis of α-methyldopa ethyl ester does not appear to be instantaneous and pharmacokinetic differences between the ester and free α-methyldopa have been demonstrated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00562310
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  • 2
    Electronic Resource
    Electronic Resource
    Pharmacokinetic and concentration-effect relationships of clonidine in essential hypertension (1977)
    Springer
    European journal of clinical pharmacology 12 (1977), S. 463-469 
    Details
    ISSN: 1432-1041
    Keywords: Essential hypertension ; clonidine ; plasma levels ; concentration-effect
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The effect of oral doses of 300 µg of clonidine hydrochloride on blood pressure, sedation and saliva production in 5 essential hypertensives were qualitatively similar to the effects in normotensive subjects. Peak plasma clonidine concentration (1.34±0.28 ng/ml) and plasma half-life (10.0 ±0.8 h) were similar to normotensives. During chronic oral dosing there was no evidence of drug accumulation. Some tolerance to the sedative and salivary flow effects occurred but no tolerance to the hypotensive effect was observed. There was a linear relationship between reduction in saliva flow and plasma levels of clonidine. The hypotensive effect was also related to plasma level at low concentrations. At plasma levels 〉1.5 ng/ml the hypotensive effect was diminished. This loss of effect at high plasma concentration may be related to the peripheral, post-synaptic alpha-adrenoceptor agonist action of the drug.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00561067
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  • 3
    Electronic Resource
    Electronic Resource
    Changes in blood pressure, heart rate, and sympathetic activity on abrupt withdrawal of tiamenidine (HOE 440) in essential hypertension (1980)
    Springer
    European journal of clinical pharmacology 18 (1980), S. 449-454 
    Details
    ISSN: 1432-1041
    Keywords: tiamenidine ; rebound hypertension ; plasma noradrenaline ; metanephrines ; urinary catecholamines
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary A limitation of clonidine therapy is the syndrome of rebound hypertension and sympathetic overactivity after withdrawal. Ten patients, four male, six female, aged 28–64 years, with essential hypertension, were treated for one year with an imidazoline derivative, tiamenidine. Blood pressure fell from an average of 178/108 mm Hg pretreatment to 152/86 mm Hg after 1 year. Tiamenidine was then withdrawn in hospital, replaced by identical placebo under single blind conditions and observations made over 96 h. The study was interrupted in five patients (4 patients within 36 h) because blood pressure rose to greater than 30 mm Hg (systolic) or greater than 20 mm Hg (diastolic) above pretreatment values. For the group, blood pressure was maximal at 194/112 mm Hg, 18 h post withdrawal, significantly higher than pretreatment (p〈0.005). Headache, tremor, flushing and insomnia were noted. Saliva production rose 100% at 24 h. Plasma noradrenaline rose within 24 h with an accompanying rise in urinary metanephrine and catecholamine excretion. Tiamenidine appears to share with other imidazolines rebound cardiovascular and autonomic effects following abrupt withdrawal.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00874654
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  • 4
    Electronic Resource
    Electronic Resource
    Withdrawal of guanfacine after long-term treatment in essential hypertension (1981)
    Springer
    European journal of clinical pharmacology 19 (1981), S. 19-24 
    Details
    ISSN: 1432-1041
    Keywords: hypertension ; guanfacine ; central antihypertensives ; withdrawal ; catecholamines
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary 1. Guanfacine (2–6 mg/day) a centrally acting antihypertensive drug, was effective in controlling blood pressure in 5 essential hypertensives and lowered plasma noradrenaline and urinary catecholamine excretion. 2. Withdrawal of guanfacine by blind substitution of identical placebo tablets under observation in hospital led to a gradual recovery of blood pressure over 2–4 days. 3. Salivary flow, which was reduced on guanfacine, returned to pretreatment levels by 2 days after withdrawal and significantly exceeded control for the next two days. 4. Urinary catecholamine excretion returned to pretreatment levels by 3 days but did not exceed control levels during the period of study. 5. Plasma noradrenaline returned gradually to pretreatment levels, and by day 4 significantly exceeded them. 6. No patient experienced symptoms suggesting catecholamine excess although four out of five reported a headache from the second day onwards. 7. Guanfacine, a centrally acting drug which pharmacologically resembles clonidine, has a slow offset of hypotensive effect over 2–3 days. Symptoms or biochemical evidence of catecholamine excess were not encountered within 48 h of withdrawal, possibly reflecting the longer duration of action and plasma half-life of guanfacine.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00558376
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  • 5
    Electronic Resource
    Electronic Resource
    Pharmacokinetics of endralazine (1984)
    Springer
    European journal of clinical pharmacology 26 (1984), S. 661-661 
    Details
    ISSN: 1432-1041
    Keywords: endralazine ; hypertension ; elimination half-liefe ; compartment model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00543509
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  • 6
    Electronic Resource
    Electronic Resource
    Clinical pharmacological studies with the vasodilator endralazine in patients with renal impairment (1984)
    Springer
    European journal of clinical pharmacology 27 (1984), S. 159-163 
    Details
    ISSN: 1432-1041
    Keywords: endralazine ; renal impairment ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The influence of renal impairment on the pharmacokinetics of endralazine was studied in 12 patients; 4 patients on regular haemodialysis therapy (creatinine clearance less than 5 ml/min) and 8 patients with varying degrees of renal impairment (creatinine clearance 11–52 ml/min). Following an oral dose of 10 mg endralazine the mean terminal elimination half-life (βt1/2) in the dialysis sub-group was prolonged at 7.1 h (range 3.3 to 14 h), compared to 3.6 h in the other renal patients (and compared to 2.3 h in hypertensive patients with normal renal function). After one week's therapy with 10 mg B.D. endralazine in the 8 patients with moderate renal impairment there was a significant increase in βt1/2 to 8.6 h but there was no significant change in the area under the drug concentration-time curve and no evidence of drug accumulation. In this study those patients with the poorest renal function had the longest βt1/2 after acute dosing. There was a significant correlation between creatinine clearance and acute βt1/2 but there was considerable variability in individual patients and, even with severe degrees of renal impairment, major dose adjustments do not appear necessary.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00544039
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  • 7
    Electronic Resource
    Electronic Resource
    The effect of the calcium antagonist nifedipine on pressor and aldosterone responses to angiotensin II in normal man (1983)
    Springer
    European journal of clinical pharmacology 25 (1983), S. 285-285 
    Details
    ISSN: 1432-1041
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00543806
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  • 8
    Electronic Resource
    Electronic Resource
    The effect of cimetidine on the pharmacokinetics, pharmacodynamics and alpha1-adrenoceptor responsiveness of trimazosin in man (1985)
    Springer
    European journal of clinical pharmacology 29 (1985), S. 301-306 
    Details
    ISSN: 1432-1041
    Keywords: trimazosin ; cimetidine ; pharmacokinetics ; alpha-adrenoceptor antagonism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The effect of cimetidine treatment on the pharmacokinetics and pharmacodynamics of single doses of trimazosin was studied in 6 normotensive volunteers. Co-administration of cimetidine did not significantly affect the overall magnitude of the hypotensive effect of trimazosin. However, the time profile of the blood pressure response was significantly modified particularly with attenuation of the delayed component. Co-administration of cimetidine did not alter alpha1-adrenoceptor antagonism by trimazosin. There was no significant change in the clearnace and volume of distribution of trimazosin but there was a significant reduction in the area under the concentration-time curve for the metabolite, 1-hydroxytrimazosin. The reduction in the AUC of 1-hydroxy-trimazosin corresponds in time with the attenuation of the delayed hypotensive response. This is consistent with the suggestion that the delayed hypotensive response is related to an active metabolite, probably 1-hydroxytrimazosin.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00544084
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  • 9
    Electronic Resource
    Electronic Resource
    In vivo and in vitro studies of the site of inhibitory action of omeprazole on adrenocortical steroidogenesis (1988)
    Springer
    European journal of clinical pharmacology 35 (1988), S. 625-629 
    Details
    ISSN: 1432-1041
    Keywords: omeprazole ; cortisol synthesis ; urinary steroid metabolites ; cholesterol cleavage inhibition ; adrenal steroidogenesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The site of omeprazole inhibition of adrenal steroidogenesis has been sought in vivo by analyzing the patterns of urinary steroid metabolite excretion after 6 days of treatment with placebo/omeprazole. Excretion rates of androsterone, aetiocholanolone, dehydroepiandrosterone, 11 β hydroxyandrosterone, tetrahydrocortisone, tetrahydrocortisol and α cortolone were reduced, indicating a block at an early step in steroidogenesis, possibly cholesterol side-chain cleavage. In vitro studies have confirmed this finding by measuring conversion of added precursors to cortisol in isolated bovine adrenocortical cells. Cortisol synthesis from added 20 α hydroxycholesterol was inhibited by 83% in the presence of 100 µg omeprazole/ml. Conversion from pregnenolone and progesterone and their 17 α hydroxylated derivatives was inhibited by 20–40% whereas cortisol production from added 11 deoxycortisol was not affected. These data suggest that omeprazole primarily inhibits cholesterol cleavage and does not inhibit 3 β hydroxysteroid dehydrogenase, 17 α hydroxylase or 11 β hydroxylation; 21 hydroxylase activity may be marginally attenuated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00637598
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  • 10
    Electronic Resource
    Electronic Resource
    The effects of desmethylimipramine on the pharmacological actions of alpha methyldopa in man (1979)
    Springer
    European journal of clinical pharmacology 16 (1979), S. 75-80 
    Details
    ISSN: 1432-1041
    Keywords: methyldopa ; hypotension ; tricyclic antidepressants ; drug interactions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The effect of pretreatment with the tricyclic antidepressant desmethylimipramine (DMI) 75 mg daily for 3 days on the action of oral methyldopa 750 mg was investigated in a double blind crossover design in volunteers. DMI pretreatment caused a small but not significant increase in supine systolic and diastolic blood pressure and heart rate. However, the effects of methyldopa on lying and standing blood pressure and heart rate were not markedly altered by pretreatment. In particular, the fall in standing blood pressure after methyldopa was present with and without DMI and the sedative action of methyldopa was similar. DMI alone reduced saliva production. No evidence was found that tricyclic antidepressant drugs significantly modify the hypotensive effect of methyldopa in man.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00563110
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