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Biomedical subjects

J D Nichols

Publications and source records attributed to J D Nichols.

9 recordsLinked to original sources
PubMed1991

The comparative bioavailability of cimetidine-alginate treatments.

The comparative bioavailability of cimetidine in cimetidine-alginate combinations has been investigated in twelve healthy volunteers in an open crossover study. Each volunteer received a single oral dose of a commercially available alginate-cimetidine combination tablet (Algitec) or cimetidine tablets (Tagamet), co-administered with a commercially available alginate reflux suppressant liquid or tablet (Gaviscon). No significant differences were observed between treatments for Cmax, tmax, AUC0-12 or AUC0- infinity. The study demonstrated equivalent bioavailability of cimetidine when administered separately with alginate products and as a fixed dose combination product.

Administration, Oral↗
PubMed1989

Application of a modified colorimetric enzyme assay to monitor plasma paracetamol levels following single oral doses to non-patient volunteers.

A modified enzyme-based colorimetric method has been used to determine plasma paracetamol profiles following single dose (2 x 500 mg) administration of three dosage forms to non-patient volunteers. The assay is linear over the concentration range 0.15-60 micrograms ml-1 with a coefficient of variation of 9.1% at the 1.5 micrograms ml-1 level. It is rapid, requiring small sample volumes; compares favourably with other techniques such as HPLC; and is not subject to interference from paracetamol metabolites and other drugs. Administration of paracetamol as two different dosage forms, as a solid tablet and as a dispersible tablet, resulted in no statistically significant difference in pharmacokinetic parameters between treatments.

Acetaminophen↗
PubMed1989

Determination of underivatised efaroxan and idazoxan in blood plasma by capillary gas chromatography with mass-selective detection.

Sensitive and specific methods for the determination of efaroxan and idazoxan in blood plasma have been developed based on solvent extraction, chromatographic separation and quantification by selected-ion monitoring using a quadruple mass-selective detector. The use of a short non-polar bonded-phase capillary gas chromatography (GC) column facilitated rapid separation of the compounds of interest from internal standards, metabolites and endogenous material. Of equal significance was the ability to chromatograph these basic compounds without prior derivatisation. The application of bonded-phase capillary GC coupled to selected-ion monitoring resulted in robust analytical procedures with sub-ng ml(-1) sensitivity and high selectivity.

Adrenergic alpha-Antagonists↗
PubMed1986

The pharmacokinetics after intravenous and oral administration in man of the alpha 2-adrenoreceptor antagonist idazoxan (RX781094).

A high performance liquid chromatographic method was developed for the quantitative determination of idazoxan in plasma. The assay was used to study the disposition of the drug after intravenous infusion and oral administration to five normal subjects. After i.v. administration the kinetics could be described by a two compartment model with a mean elimination half life of 4.20 h. The mean calculated volume of distribution during the elimination phase was 3.20 l/kg-1 and the mean plasma clearance was 824 ml min-1. After oral administration a lag period before onset of absorption was observed in all five volunteers, the plasma levels declining monoexponentially from the peak concentration with a mean elimination half life of 5.58 h. The absolute availability varied between 26% and 41% with a mean value of 34%. In-vitro measurements produced a blood/plasma ratio of 1.3 for idazoxan.

Administration, Oral↗
PubMed1986

Constant-parameter capture-recapture models.

Jolly (1982, Biometrics 38, 301-321) presented modifications of the Jolly-Seber model for capture-recapture data, which assume constant survival and/or capture rates. Where appropriate, because of the reduced number of parameters, these models lead to more efficient estimators than the Jolly-Seber model. The tests to compare models given by Jolly do not make complete use of the data, and we present here the appropriate modifications, and also indicate how to carry out goodness-of-fit tests which utilize individual capture history information. We also describe analogous models for the case where young and adult animals are tagged. The availability of computer programs to perform the analysis is noted, and examples are given using output from these programs.

Aging↗
PubMed1981

Pharmacokinetics of intravenous and oral tolmesoxide.

A high pressure liquid chromatographic assay was developed for simultaneous measurement of the plasma levels of tolmesoxide and its principal metabolite, RX71112. The assay was used to study the disposition of intravenous and oral tolmesoxide in ten normotensive subjects. Two exponential terms were required to describe the disposition of the drug following intravenous administration, whilst a single exponential term sufficed to account for the decay in the plasma concentration after oral administration. The bioavailability of oral tolmesoxide from capsules averaged 84.5% and was independent of dose. The mean half-life after i.v. dosing was 2.6 h (+/- 0.3 SEM) compared to values of 1.9 h (+/- 0.1 SEM) and 2.7 h (+/- 0.5 SEM) following 200 and 400 mg oral doses respectively. In all subjects RX71112 appeared in plasma shortly after tolmesoxide following both routes of administration. The terminal half-life of the metabolite was significantly longer than tolmesoxide with a mean value of 4.9 h (+/- 0.9 SEM) following the 200 mg oral dose of tolmesoxide. The binding of tolmesoxide and RX71112 at therapeutic plasma concentration was 36.8% (+/- 0.5 SEM) and 58.5% (+/- 0.3 SEM) and this remained unchanged at higher concentrations.

Administration, Oral↗
PubMed1980

Pharmacokinetics of fenclofenac following single and multiple doses.

The plasma concentration of the anti-inflammatory drug fenclofenac was investigated in volunteers following single oral doses of 200, 500 and 600 mg, as well as multiple doses of 600mg b.i.d. over five days, using gas chromatography with electron capture detection. The pharmacokinetic parameters derived were independent of dose, and the terminal half-life, t1/2, varied independently of dose between 20 and 38 hours (27.23 +/- 1.8 at 600mg). The apparent volume of distribution (Vd area) had similar values at doses of 200, 500 and 600mg of 15.2 +/- 2.6, 18.2 +/- 1.5 and 14.7 +/- 1.7 litres respectively. These small volumes of distribution indicate that fenclofenac distributes mainly into extracellular space. A mean peak plasma concentration of 63.5 +/- 4.6microgram/ml developed after 3 to4 hours following a single 600mg dose whilst a mean steady state plasma concentration (600mg b.i.d.) of 86.9 +/- 5.7 microgram/ml was achieved within four days, and this decayed with a mean terminal half-life of 25.9 +/- 4.2 hours.

Adult↗
PubMed1975

A simultaneous determination of acetylsalicylic acid, salicylic acid and salicylamide in plasma by gas liquid chromatography.

A novel method for the simultaneous determination of acetylsalicylic acid, salicylic acid and salicylamide in biological fluids by gas liquid chromatography is described. The assay has been used to determine the plasma concentration of salicylates in 10 volunteers after oral ingestion of three commercially available aspirin-containing formulations. No difficulty was encountered in determining low concentrations of acetylsalicylic acid in the presence of higher concentrations of salicylic acid. The in vivo plasma half life of acetylsalicylic acid in man was found to be 15.5 min.

Administration, Oral↗