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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 24 (1983), S. 777-785 
    ISSN: 1432-1041
    Keywords: aspirin ; migraine ; salicylic acid ; metoclopramide ; drug absorption ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of aspirin (ASA) in acute migraine attacks, and the influence of metoclopramide on ASA disposition, were studied in 32 attacks in 30 patients. An intergroup comparison was made between normal volunteers, and the migraineurs, who were assigned at random to one of three treatment groups: a) oral ASA only (900 mg); b) 10 mg oral metoclopramide + oral ASA 900 mg; c) 10 mg i. m. metoclopramide + oral ASA 900 mg. Plasma ASA and SA levels were measured serially over 2 h, and the resultant data evaluated pharmacokinetically. Metoclopramide plasma levels were also determined over 2 h, and the results compared with a second group of normal volunteers. The rates of oral ASA absorption and elimination were unaffected by migraine. Mean absorption rate constants of 14.15±9.48 h−1 (normals), 7.91±3.42 h−1 (ASA only), 6.74±3.26 h−1 (ASA + oral metoclopramide) and 8.12±2.82 h−1 (ASA + i. m. metoclopramide) were calculated. Mean elimination rate constants ranged from 2.56 h−1 to 3.37 h−1, and did not differ significantly between controls and migrainous patients. Values for absorption lag time, however, were higher in migraine patients treated with ASA alone than in any other group. The amount of ASA absorbed unhydrolysed was also lower in this group. SA levels appeared unaffected either by the migraine attack, or by metoclopramide administration, over the period of study. Metoclopramide plasma levels were significantly lower during migraine attacks, and the amount of drug absorbed up to 2 h from dosing was also reduced, as compared with non-migrainous subjects. It was concluded that acute migraine caused a delay in orally administered ASA reaching its absorption sites, probably as a result of gastric stasis, and may have decreased the amount of ASA absorbed. The prior administration of metoclopramide, either orally or intramuscularly, reduced the absorption lag time, and thus promoted the early absorption of ASA, probably by restoring alimentary tract motility.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1041
    Keywords: spironolactone ; canrenone ; metabolites ; pharmacokinetics ; single/multiple oral doses ; healthy volunteers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of canrenone and ‘total metabolites’ after base hydrolysis was studied in eight young volunteers following single and multiple dose oral administration of spironolactone. The plasma levels of canrenone and ‘total metabolites’ were fitted to a two-compartment open model with a first-order absorption process. From our eight normal subjects studied, the harmonic mean of the distributive half-life (t1/2α) of canrenone was found to be 1.66 h, and the harmonic mean of the terminal elimination half-life (t1/2β) to be 22.6 h. Harmonic means of the distributive and elimination half-lives of ‘total metabolites’ after base hydrolysis were 2.48 h and 28.8 h respectively. The accumulation ratio of canrenone was 2.53, whereas that of ‘total metabolites’ was 1.89. Despite the fact that spironolactone has been shown to induce hepatic metabolism of other drugs, no evidence of autoinduction was noted in the present study, as plasma levels of canrenone and ‘total metabolites’ were found to obey a linear two-compartment model with reproducible absorption and disposition after single and multiple doses.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 26 (1984), S. 381-388 
    ISSN: 1432-1041
    Keywords: midazolam ; hypnotic drug ; benzodiazepine ; pharmacokinetics ; aged patients
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of midazolam, an imidazo-benzodiazepine derivative, have been studied in 13 subjects over the age of 60 years who received the drug intravenously (0.07 mg kg−1) as an induction agent for endoscopy. Two to three days later, 6 of these subjects received 5 mg of midazolam intramuscularly, and another 6 of the subjects received 10 mg of the drug orally. The plasma concentration-time curves were again studied pharmacokinetically. After intravenous dosing, the mean (± SD) elimination half-life (2.14±1.24 h) showed a statistically significant trend to increase with age in the subjects older than 60 years. While the mean (± SD) clearance value (0.30±0.19 l kg−1h−1) tended to fall with age in the elderly subjects, this trend was not statistically significant. Apparent volume of distribution did not appear to be related to advancing age beyond 60 years, and this parameter (mean ± SD) did not differ to a statistically significant extent between the aged subjects (0.77±0.47 l kg−1) and the young subjects studied previously (1.09±0.58 l kg−1). Atropine premedication did not appear to alter the dispositional parameters of the intravenously administered drug. Intramuscularly administered midazolam was absorbed rapidly. Bioavailability appeared incomplete (F=0.59±0.15, mean ± SD), possibly due to saturable elimination of the drug at the higher plasma levels which were obtained after intravenous midazolam. Oral bioavailability, relative to intravenous, was 0.34±0.17, (mean ± SD), with an appreciable but variable lag time (0.74±0.40 h, mean ± SD). Orally, in the dose used, the drug was an inefficient hypnotic with four of the six subjects failing to attain the plasma drug level of 44–50 µg l−1, which appeared to be the approximate threshold for sleep. It is impossible to know whether this failure represents an age related effect on drug absorption, or is a consequence of the upper alimentary tract abnormalities for which the endoscopies were done.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 25 (1983), S. 65-67 
    ISSN: 1432-1041
    Keywords: tizanidine ; pharmacokinetics ; spasticity ; multiple sclerosis ; haematological parameters ; electromyogram
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The time-course of plasma concentrations of the antispasticity agent tizanidine were measured by a specific radioimmune-assay in six adults who had severe spasticity due to multiple sclerosis. The drug was given as a single oral 4 mg dose to each subject. The drug had a mean absorption half-life of 0.30±0.155 h following a mean lagtime of 0.361±0.118 h, and a mean terminal elimination half-life of 4.16±2.06 h. Only 2.65±0.82% of the dose was excreted unchanged in urine in 2 h. Calculated values of clearance and apparent volume of distribution were almost certainly overestimates as it seems probable that the orally-administered drug undergoes significant presystemic elimination (its bioavailability was not determined in the investigation here reported). Relief of spasticity, from the dosage used, was relatively slight and appeared greatest at the time of peak plasma levels of the drug.
    Type of Medium: Electronic Resource
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