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Biomedical subjects

W A McGowan

Publications and source records attributed to W A McGowan.

8 recordsLinked to original sources
PubMed1982

The 'induction' dose of thiopentone. A method of study and preliminary illustrative results.

Study of the minimal dose requirements for induction of anaesthesia poses great problems which are solved by the use of a standard administration technique and the abolition of the eyelash reflex as an endpoint. This has been used in 2206 consecutive unselected inductions, in which variables considered to be likely to influence the dosage were recorded. Milligram per kilogram is the most acceptable method of expressing the average dosage of thiopentone. Doses follow a right skew distribution. Women required a significantly lower average dose of thiopentone than men, while obese patients required less than others. Moderate or heavy drinking increased the induction dose but the use of tobacco did not have any influence. The most important factors governing dosage are the physical fitness of the patient and the premedication used. Patients in ASA grades 1 and 2 required significantly more thiopentone than those in grades 3 and 4. This effect is as great as that of premedication in which an opiate with a phenothiazine or hyoscine markedly reduced the induction dose. It was more important than the patient's pre-operative condition with respect to sedation or apprehension. Small doses of opiates or benzodiazepines do not have as much effect on dosage.

Adolescent↗
PubMed1982

The effect of intravenous cimetidine on the absorption of orally administered diazepam and lorazepam.

1 The effect of intravenous cimetidine 200 mg or 400 mg on the absorption of lorazepam 2.5 mg tablet and diazepam 10 mg tablet and capsule was studied. 2 Considerable individual variation in plasma concentrations was found with all preparations. 3 Cimetidine increased the absorption of diazepam and lorazepam. 4 Capsule preparations of diazepam generally produced higher drug plasma concentrations than the tablets.

Administration, Oral↗
PubMed1981

The placental transfer of cimetidine.

The placental transfer of cimetidine 200 mg intravenously was investigated in 16 patients in normal labour and 40 patients undergoing elective Caesarean section. Cimetidine crosses the placental barrier, blood levels at delivery in mothers and infants being lower with increasing time from injection. Umbilical cord blood cimetidine levels are markedly lower than those of the mother during the first hour following administration but thereafter levels are similar. The mean fetal-maternal ratio at delivery was highest (0.84) at 1 1/2-2 hours following administration. Postdelivery infant and maternal blood samples showed that cimetidine could not be detected, in most cases, 19 hours following administration. The relevance of these findings is discussed.

Cesarean Section↗
PubMed1980

Another look at acute tolerance to thiopentone.

The phenomenon of "acute tolerance" to thiopentone was re-examined in 82 subjects with induction doses of 2-15mg kg-1. There was a strong positive correlation between the venous plasma thiopentone concentrations on recovery from anesthesia and the induction dose, expressed as either mg kg-1 or mg m-2. Recovery time was proportionately shorter with larger doses, being directly related to log10 of the plasma concentration at awakening.

Anesthesia, Intravenous↗
PubMed1980

Comparison of the subjective effects and plasma concentrations following oral and i.m. administration of flunitrazepam in volunteers.

Flunitrazepam 0.5, 1.0 or 2.0 mg was given by the oral or i.m. routes to groups of volunteers and its effects compared. Plasma concentrations of the drug were estimated by gas-liquid chromatography, in a smaller number of the subjects. The most striking effect was sedation which increased with the dose, 2 mg producing deep sleep although the subjects could still be aroused. The effects of i.m. administration were apparent earlier and sometimes lasted longer than those following oral administration. Dizziness was less marked than sedation, but increased with the dose. There was pain on i.m. injection of flunitrazepam significantly more often than with isotonic saline. Plasma concentrations varied with dose and route and corresponded qualitatively with the subjective effects. The drug was still present in measurable quantities after 24 h even with the smallest dose.

Administration, Oral↗
PubMed1980

Comparison of the subjective effects and plasma concentrations following oral and i.m. administration of flunitrazepam in patients.

The use of flunitrazepam 1 and 1.5 mg was compared as a premedicant with diazepam 10 mg and lorazepam 2.5 mg. Plasma flunitrazepam concentration were measured after oral and i.m. administration. Flunitrazepam and diazepam had a similar onset time and duration of action, both being more rapid in onset and shorter in duration than lorazepam I.m. flunitrazepam had a slightly greater sedative effect than oral flunitrazepam and plasma concentrations correlated well with the onset of the sedative effect by either route of administration. The i.m. injection of flunitrazepam was not as painful as that of diazepam, but slightly more painful than lorzepam. A second peak occurred at about 5 h and flunitrazepam was still detectable at 48 h. The plasma half-life was 3-4 h.

Administration, Oral↗
PubMed1979

Comparison of the actions of diazepam and lorazepam.

Diazepam and lorazepam differ in potency and in the time-course of their action. As a sedative, diazepam 10 mg is equivalent to lorazepam 2-2.5 mg. Diazepam is better absorbed after oral than after i.m. administrations but this does not apply to lorazepam. The clinical effect and amnesia begin more rapidly with diazepam, but last longer following lorazepam. Lorazepam is more effective than diazepam in blocking the emergence sequelae from ketamine. Lorazepam i.v. is followed by a lesser frequency of venous thrombosis.

Amnesia↗