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Biomedical subjects

A McHarg

Publications and source records attributed to A McHarg.

8 recordsLinked to original sources
PubMed2000

The in vivo pharmacological profile of eletriptan (UK-116,044): a potent and novel 5-HT(1B/1D) receptor agonist.

The anti-migraine drug, eletriptan [(R)-3-(1-methyl-2-pyrrolidinylmethyl)-5-[2-(phenylsulphonyl )ethyl]-1 H-indole; UK-116,044], is a novel 5-HT(1B/1D) receptor agonist. In this paper, the regional vasoconstrictor profile of eletriptan, in comparison with sumatriptan, was examined in the anaesthetised dog. The inhibitory actions of eletriptan on neurogenic inflammation in rat dura mater were also assessed. In the anaesthetised dog, eletriptan (1-1000 microg kg(-1) i.v.) produced a dose-dependent reduction of carotid arterial blood flow with a similar potency and maximum effect to sumatriptan (ED(50) values: eletriptan and sumatriptan, 12 and 9 microg kg(-1), i.v., respectively). However, eletriptan exhibited a significantly lower potency than sumatriptan in reducing coronary artery diameter (ED(50) values: 63 and 19 microg kg(-1), i.v., respectively, P<0.05). In the femoral circulation, sumatriptan caused a significant reduction in arterial blood flow (ED(50) 35 microg kg(-1) i.v.) whereas eletriptan (1-1000 microg kg(-1) i.v.) had no significant effect upon femoral arterial blood flow when compared to vehicle-treated animals. In rats, eletriptan (30-300 microg kg(-1) i.v.) administered prior to electrical stimulation of the trigeminal ganglion produced a dose-related and complete inhibition of plasma protein extravasation in the dura mater (mean extravasation ratio: control 1.9; eletriptan 1.0, minimum effective dose 100 microg kg(-1), P<0.05). The potency and maximum effect of eletriptan was identical to that of sumatriptan in this model. When administered during a period of continual stimulation of the trigeminal nerve, eletriptan (100 microg kg(-1) i.v.) produced a complete inhibition of plasma protein extravasation. The ability to reduce canine carotid arterial blood flow and inhibit neurogenic inflammation in rat dura mater suggests that vascular and neurogenic mechanisms may contribute to eletriptan's clinical efficacy in migraine patients. In addition, eletriptan exhibits some selectivity for reducing carotid arterial blood flow when compared with femoral arterial blood flow and coronary artery diameter, in the anaesthetised dog.

Anesthesia↗
PubMed2000

Pharmacology and efficacy of eletriptan for the treatment of migraine attacks.

Sumatriptan, a 5-HT 1B/1D agonist, was introduced 10 years ago and was the most effective therapy for migraine attacks at that time. Eletriptan is a new 5-HT 1B/1D agonist with high potency and selectivity at 5-HT 1B/1D receptors. It is effective in animal models in which the vascular and neurogenic mechanisms implicated in migraine were measured. Eletriptan is selective for the intracranial blood vessels over other extracranial vasculature, in particular coronary arteries. Eletriptan has a rapid and complete oral absorption and a good oral bioavailability in migraineurs. In comparative trials 20 mg, 40 mg and 80 mg eletriptan, 100 mg sumatritpan and placebo were compared for the treatment of migraine attacks. All three doses of eletriptan were statistically superior to placebo for headache response and headache-free patients. The 80 mg dose of eletriptan was also superior to sumatriptan 100 mg. Headache recurrence, defined as return of moderate or severe headache within 24 hours of dosing and following a headache response at two hours after initial dosing, occurred in 33% of the patients following 100 mg sumatriptan and in 28%, 34% and 32% after 20 mg, 40 mg and 80 mg eletriptan. In another large trial, headache response rates were significantly higher for both doses of eletriptan (64% for 40 mg and 67% for 80 mg) than for two doses of sumatriptan (50% for 50 mg and 53% for 100 mg). Eletriptan 40 mg or 80 mg was also superior to ergotamine plus caffeine (Cafergot). In summary, eletriptan is a highly effective and fast-acting drug for the treatment of acute migraine attacks.

Double-Blind Method↗
PubMed1999

Characterisation of the 5-HT receptor binding profile of eletriptan and kinetics of [3H]eletriptan binding at human 5-HT1B and 5-HT1D receptors.

The affinity of eletriptan ((R)-3-(1-methyl-2-pyrrolidinylmethyl)-5-[2-(phenylsulphonyl )ethyl]-1H-indole) for a range of 5-HT receptors was compared to values obtained for other 5-HT1B/1D receptor agonists known to be effective in the treatment of migraine. Eletriptan, like sumatriptan, zolmitriptan, naratriptan and rizatriptan had highest affinity for the human 5-HT1B, 5-HT1D and putative 5-ht1f receptor. Kinetic studies comparing the binding of [3H]eletriptan and [3H]sumatriptan to the human recombinant 5-HT1B and 5-HT1D receptors expressed in HeLa cells revealed that both radioligands bound with high specificity (>90%) and reached equilibrium within 10-15 min. However, [3H]eletriptan had over 6-fold higher affinity than [3H]sumatriptan at the 5-HT1D receptor (K(D)): 0.92 and 6.58 nM, respectively) and over 3-fold higher affinity than [3H]sumatriptan at the 5-HT1B receptor (K(D): 3.14 and 11.07 nM, respectively). Association and dissociation rates for both radioligands could only be accurately determined at the 5-HT1D receptor and then only at 4 degrees C. At this temperature, [3H]eletriptan had a significantly (P<0.05) faster association rate (K(on) 0.249 min(-1) nM(-1)) than [3H]sumatriptan (K(on) 0.024 min(-1) nM(-1)) and a significantly (P<0.05) slower off-rate (K(off) 0.027 min(-1) compared to 0.037 min(-1) for [3H]sumatriptan). These data indicate that eletriptan is a potent ligand at the human 5-HT1B, 5-HT1D, and 5-ht1f receptors and are consistent with its potent vasoconstrictor activity and use as a drug for the acute treatment of migraine headache.

Animals↗
PubMed1999

Characterisation of the contractile activity of eletriptan at the canine vascular 5-HT1B receptor.

The functional activity of eletriptan ((R)-3-(1-methyl-2-pyrrolidinylmethyl)-5-[2-(phenylsulphonyl )ethyl]- 1 H-indole) at the contractile serotonin (5-hydroxytryptamine; 5-HT) '1B-like' receptor in dog isolated saphenous vein and basilar artery was investigated. Eletriptan, like 5-HT and sumatriptan potently contracted saphenous vein (pEC50: 6.3, 6.9 and 6.1, respectively) and basilar artery (pEC50 7.2, 7.5 and 6.8, respectively). The maximum responses evoked by eletriptan was, unlike sumatriptan, significantly lower than that to 5-HT (intrinsic activity saphenous vein: eletriptan 0.57, 5-HT 1.0, sumatriptan 0.85; basilar artery: eletriptan 0.77, 5-HT 0.98, sumatriptan 0.89). Contractions evoked by eletriptan were antagonised by the 5-HT1B/1D receptor antagonist GR125743 (N-[4-methoxy-3-(4-methyl piperazin-1-yl)phenyl]-3-methyl-4-(4-pyridyl)benzamide) with pA2 values of 9.1 in saphenous vein and 9.4 in basilar artery. Affinity estimates (pKA) for 5-HT and sumatriptan determined from receptor alkylation studies in saphenous vein were 6.6 and 6.3, respectively, compared to the apparent equilibrium dissociation constant (pKp) for eletriptan of 6.8. The rank order of relative intrinsic efficacies (epsilon) was 5-HT > sumatriptan > eletriptan. Thus, eletriptan required greater receptor occupancy (4.4-fold) to evoke an equivalent contraction to 5-HT and sumatriptan in dog isolated saphenous vein. These data demonstrate that eletriptan is a potent partial agonist at the canine vascular 5-HT1B receptor.

Alkylation↗
PubMed1990

Tissue aluminum concentrations stability over time, relationship to age, and dietary intake.

Aluminum concentration was measured in serum, whole blood, hair, and urine by neutron activation analysis. Seventy-six nondemented subjects were investigated. Not all assays were done on all subjects (e.g., serum aluminum on 76 subjects, whole blood aluminum on 42 subjects), but tissue aluminum concentrations were estimated on more than one occasion on 32 subjects. The mean +/- SD aluminum concentration in serum was 0.219 +/- 0.063 micrograms/ml (N = 76), in whole blood 0.368 +/- 0.091 micrograms/ml (N = 42), in urine 0.092 +/- 0.076 micrograms/ml (N = 42), and in hair 6.42 +/- 2.22 micrograms/g (N = 42). Using product moment correlation coefficient there was no significant correlation between age and tissue aluminum concentrations, nor between dietary intake of aluminum and tissue aluminum. The tissue aluminum concentrations were not stable over time even when dietary intake was constant. Tissue aluminum concentrations were measured in 14 patients after 7 days of dietary control and repeated approximately 6 weeks later, again after 7 days of dietary control. There was no significant correlation between the two estimations in any tissue measured. These results suggest that raised tissue aluminum concentrations reported in Alzheimer's disease are not an exaggeration of a normal ageing process, are not likely to be simply secondary to increased dietary aluminum intake, and that Alzheimer's disease does not represent the chronic toxic effect of moderately raised aluminum levels at the upper end of the normal distribution.

Adult↗
PubMed1987

Dementia and immobility.

Structured physical and psychiatric assessments were performed on 100 elderly women with dementia admitted to either a geriatric or a geriatric psychiatry unit, and the relationship between physical and mental factors and the ability to transfer was investigated. There was an association between limited mobility and physical and psychiatric evidence of cerebrovascular and cardiac disease; but none between mobility and most measures of degree of dementia, vision, hearing, balance, cerebellar function, position sense, ankle reflexes, postural hypotension, locomotor disease, medication or ratings for depression, anxiety, irritability, hostility, lack of co-operation, suspiciousness, or distractibility. This suggests that in dementia the main cause of limited mobility is focal neurological damage.

Aged↗
PubMed1983

Erythrocyte ouabain binding in dementia.

Age-matched patients attending a geriatric psychiatry day hospital, one group with Alzheimer's dementia and another with functional illness, were studied and compared with similar inpatient groups. Erythrocyte ouabain binding was assayed and Clifton ratings completed. In day hospital patients ouabain binding was significantly lower in the demented group (p less than 0.008) than in the functional group. There was a positive correlation between Clifton ratings and ouabain in the whole group (p less than 0.05). No significant differences were found in inpatient groups. Possible reasons for findings are discussed.

Aged↗