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Biomedical subjects

G D Burrows

Publications and source records attributed to G D Burrows.

At least 163 records · Page 9Linked to original sources
PubMed1982

Platelet monoamine oxidase activity and cigarette smoking.

Platelet MAO activity and plasma thiocyanate concentrations were determined in 72 normal volunteers (22 non-smokers and 50 smokers). Thiocyanate concentrations were used as an index of exposure to cigarette smoke. A significant negative correlation between MAO and thiocyanate concentration was observed for the group (rs = 0.35; P less than 0.005). When examined by sex, the correlation was significant for females but not for males. Mean MAO activity was significantly lower for female smokers than for female non-smokers. For males, no significant differences in MAO activity were observed between smokers and non-smokers. It is possible that smoking causes inhibition of MAO by a direct effect or by indirect effects such as altering hormone levels. Alternatively women with a low MAO activity have a greater innate tendency to smoke.

Adult↗
PubMed1982

Ligand binding and platelet uptake studies of loxapine, amoxapine and their 8-hydroxylated derivatives.

Loxapine, amoxapine and their 8-hydroxylated derivatives were studied by means of [3H]imipramine binding to rat cortical membranes, [3H]spiperone binding to rat striatal membranes, and the inhibition of serotonin uptake by human platelets. As inhibitors of [3H]imipramine binding: amoxapine greater than hydroxyamoxapine greater than loxapine = hydroxyloxapine; as inhibitors of platelet serotonin uptake: hydroxyamoxapine greater than amoxapine greater than hydroxyloxapine greater than loxapine; and as inhibitors of [3H]spiperone binding: loxapine greater than amoxapine greater than hydroxyamoxapine greater than hydroxyloxapine. The antipsychotic properties of loxapine and amoxapine were supported by the binding results, which also indicated the probable antipsychotic activities of the metabolites. All 4 compounds may possess dual action of antidepressant effect as well as antipsychotic effect.

Amoxapine↗
PubMed1982

Monitoring and interpretation of antidepressant plasma concentrations.

A brief review of the factors influencing plasma tricyclic concentrations and the relationship between clinical response and plasma concentration is presented. It is concluded that routine monitoring of tricyclics is unwarranted. In some specific instances monitoring tricyclic antidepressant plasma concentrations may be indicated: in cases of therapeutic failure a low level may indicate poor compliance or rapid metabolism and the need to increase the dose; for the management of side effects, especially when cardiac abnormalities exist prior to therapy; in cases of polypharmacy when drug interactions can occur; the management of overdoses and in patients with physical illnesses especially renal and hepatic disease. The elderly also constitute a group of patients in whom drug monitoring may be advisable. This group of patients tends to develop higher plasma levels than younger patients on equivalent doses. Some guidelines for the interpretation of laboratory results are presented and discussed.

Age Factors↗
PubMed1981

Multicentre evaluation of mianserin in depressive illness.

A multicentre evaluation of the effectivensss of mianserin in depressive illness was carried out. A total of 130 patients were treated with the drug, but useful data were collected on 55 patients; of these 36 responded to mianserin. A number of unwanted side effects were recorded. They were generally of mild to moderate severity, but occasionally were severe enough to warrant withdrawal of mianserin therapy. Mianserin was considered to be an effective antidepressant.

Adult↗
PubMed1981

Simultaneous measurement of dothiepin and its major metabolites in plasma and whole blood by gas chromatography-mass fragmentography.

A method for the simultaneous measurement of dothiepin and two of its major metabolites, northiaden and dothiepin S-oxide in both plasma and whole blood is described. The method involves the use of gas chromatography-mass fragmentography. It is selective, sensitive (1 microgram/1) and reproducible. It has been used to analyse both plasma and blood samples following single oral doses of 75 mg dothiepin in seven volunteers.

Adult↗
PubMed1981

Pharmacokinetics of N-desmethyldiazepam after a single oral dose of clorazepate: the effect of smoking.

The pharmacokinetics of N-desmethyldiazepam was evaluated after oral administration of clorazepate 20 mg to 12 healthy male volunteers (6 smokers; 6 non-smokers), aged 23-29 years. Plasma levels of desmethyldiazepam were measured by gas liquid chromatography. The half life of elimination (t1/2 beta) was significantly longer in the non-smoking volunteers than in the smokers: 54.7 +17.7 versus 29.8 +9.9 h (p less than 0.05). Peak plasma concentrations (Cmax) were higher in non-smokers than in smokers, 413 +106 micrograms/l and 245 +50 micrograms/l, respectively (p less than 0.05). The sedative effect of clorazepate was less severe in smokers than in non-smokers.

Administration, Oral↗
PubMed1981

Metabolism and pharmacokinetics of dothiepin.

1 Seven healthy volunteers received a single oral dose of 75 mg dothiepin. Plasma concentrations of dothiepin were measured by gas chromatography-mass fragmentography. 2 The plasma concentrations obtained were fitted to the equation Ct = Ae-a(t-tau) + Be-beta(t-tau) - Ce-ka(t-tau). The mean peak concentration was 47(33-71) microgram/l at 3(2-5) h. Mean estimates were as follows: absorption half life 1.2(0.07-3.0) h, distribution half-life 2.6(1.1-3.8) h, elimination half-life 22(14-40) h, apparent volume of distribution 45(20-92) l/kg, and oral clearance 1.36(0.88-1.8) l kg-1 h-1. 3 Blood concentrations of dothiepin were measured in comparison in five of the volunteers. The mean blood/plasma ratio was 0.7(0.6-0.8). 4 Plasma and blood concentrations of northiaden and blood concentrations of dothiepin S-oxide, two metabolites of dothiepin, were also measured. Dothiepin S-oxide was the major metabolic reaching a peak level of 81(34-150) microgram/l at 5(4-6) h. In comparison, northiaden reached a peak concentration of only 10 (3-21) microgram/l at 5 (4-9) h. The mean half-life of elimination of dothiepin S-oxide was 19 (13-35) h while that for northiaden was 33 (22-60) h.

Adult↗
PubMed1981

Determination of nomifensine plasma concentrations: a comparison of radioimmunoassay and gas chromatography.

1 A gas-liquid chromatography (g.l.c.) method for measurement of the antidepressant nomifensine was developed and compared for precision, accuracy, sensitivity and convenience with radioimmunoassay (RIA). 2 No significant difference was found between the two techniques for unconjugated nomifensine (y = 1.07x = 2.7; r = 0.996) or total nomifensine (y = 1.;02x + 0.02; r = 0.999). 3 RIA proved more sensitive than g.l.c. (detection limit of RIA being 1 microgram/l and g.l.c. 5 micrograms/l). 4 RIA was found to be a more convenient technique (up to 50 samples per day with RIA, and 16 samples with g.l.c.).

Chromatography, Gas↗
PubMed1980

An evaluation of maprotiline intravenous kinetics and comparison of two oral doses.

The kinetics of maprotiline have been evaluated in six normal volunteers following rapid intravenous administration of 75 mg. Blood levels could be resolved using a biexponential equation. Mean estimates of half-life, volume of distribution and systemic clearance were 40 +/- 15 h, 51.7 +/- 18.01/kg and 0.92 +/- 0.24/kg/h, respectively. Blood/plasma concentrations varied between subjects from 0.77 to 1.64. A comparison of the bioavailability of two oral doses (a 75 mg tablet and three 25 mg tablets) was carried out in the same volunteers. No significant difference was observed between the maprotiline concentrations obtained for the two doses at sampling times up to 26 h. No significant difference was found in the area under the concentration vs. time curves for the two doses. Equivalent bioavailability can be assumed. On the basis of the intravenous injection study, systemic bioavailability averaged 66% and 70% for the 75 mg and three 25 mg tablets respectively.

Administration, Oral↗
PubMed1980

Viloxazine plasma concentrations and clinical response.

Eleven patients suffering from primary depressive illness were treated with 300 mg/d of viloxazine for 29 days. Blood samples were collected at weekly intervals and severity of depression assessed using the Hamilton depression rating scale. Mean plasma viloxazine level for all patients during the trial was 1.20 micrograms/ml and ranged from 0.40 to 2.70 micrograms/ml. No simple relationship between plasma concentration and amelioration score was observed at day (rs = -0.02), day 22 (rs = -0.29) or day 29 (rs = 0.09). No significant difference in plasma concentrations between responders and non-responders was observed at day 29. Side effects were not correlated with plasma concentrations.

Administration, Oral↗
PubMed1980

Plasma levels of ethinyl oestradiol and norgestrel during hormone replacement therapy.

Plasma levels of levonorgestrel and ethinyl oestradiol were estimated in six women who took part in a double blind cross-over trial of hormone replacement therapy. Over a 12 mth period, each woman received each of the following oral drugs for 3 mth: ethinyl oestradiol 50 microgram, levonorgestrel 250 microgram, combination of ethinyl oestradiol 50 microgram and levonorgestrel 250 microgram (Nordiol), and placebo. Plasma samples were collected at 2, 8 and 26 h after morning medication each month. Plasma levels of norgestrel were increased when ethinyl oestradiol was added in the form of the combined preparation "Nordiol". The addition of ethinyl oestradiol to norgestrel therapy also resulted in significant differences between patients in the plasma norgestrel levels. There was approximately a three-fold difference between individuals in the plasma levels of ethinyl oestradiol achieved on the same fixed dose. No simple relationship was evident between plasma levels of norgestrel or ethinyl oestradiol and any of the clinical features measured.

Adult↗
PubMed1980

Some clinical effects of oestrogen-progestogen therapy in surgically castrated women.

This study reports some of the effects of oestrogen and progestogen therapy. forty-nine women who had undergone hysterectomy and bilateral salpingo-oophorectomy took part in a double blind crossover study during which they received ethinyl oestradiol 50 micrograms/day, norgestrel 250 micrograms/day, the combination of these substances "Nordiol" and placebo. Somatic complaints were assessed at monthly interviews and weight and blood pressure recorded. The addition of norgestrel to ethinyl oestradiol therapy resulted in less dryness of skin but significantly increased mastalgia and breast size. There were no significant differences between drugs on amount of facial hair, acne, arthralgia, pruritus vulvae, vaginal discharge, vaginal odour, dyspareunia, weight or blood pressure. There was a significant reduction of diastolic blood pressure with the time duration of the study.

Blood Pressure↗