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Biomedical subjects

C J Johansson

Publications and source records attributed to C J Johansson.

8 recordsLinked to original sources
PubMed1992

Intravenous nicotine retards transdermal absorption of nicotine: evidence of blood flow--limited percutaneous absorption.

For most drugs delivered by the transdermal route, percutaneous absorption is limited by the rate of release of the drug from the device or by diffusion across the stratum corneum. However, systemic absorption also requires that the drug be taken up by dermal blood vessels. As part of a bioavailability study of a transdermal delivery system, we observed that a concomitant intravenous infusion of nicotine had a marked effect on the absorption kinetics of transdermal nicotine. Plasma concentrations of nicotine rose less rapidly, reached a lower peak, and peaked at a later time, indicating delayed absorption of transdermal nicotine after intravenous nicotine versus after transdermal nicotine administered alone. Nicotine is known to produce cutaneous vasoconstriction. The likely explanation for our observation is that intravenous nicotine constricts dermal blood vessels, thereby limiting percutaneous absorption. Other vasoconstrictor drugs would be expected to retard the absorption of transdermal nicotine and perhaps other transdermal drugs as well.

Administration, Cutaneous↗
PubMed1992

Efficacy of a topical nasal decongestant in different formulations: the effect of viscosity.

Factors affecting the absorption of drugs through the nasal mucosa are increasingly being studied. Dosage form factors, i.e. the viscosity of the excipients, have been claimed to be of importance for enhanced nasal absorption due to prolongation of contact time between drug and mucosa. In the present study, a comparison was made of the effect of a local nasal sympathomimetic when administered intranasally in formulations with different viscosities. Volunteers received the test drugs as nasal sprays in a randomized cross-over design by a rhinomanometric technique, the effect of the drug being recorded for up to 5 h after administration. No significant differences in effects were observed when the test formulations were compared.

Absorption↗
PubMed1991

Absolute bioavailability of nicotine applied to different nasal regions.

The absolute bioavailability of nicotine administered nasally, as drops to the nasal conchae and nasal septum, and as a nasal spray, has been studied in eight healthy volunteers. Single nasal doses of 1 mg nicotine were given and plasma concentrations of nicotine were followed for 6 h. Compared to an intravenous infusion of nicotine, the bioavailability of the nasal administrations was 60 to 75%. The rate of absorption was fast, the maximum concentration being reached after about 10 min. In the present study, there was no significant difference in the rate or extent of absorption between the different nasal treatments.

Absorption↗
PubMed1991

A pharmacokinetic study of prednimustine as compared with prednisolone plus chlorambucil in cancer patients.

The pharmacokinetic characteristics of prednisolone and of chlorambucil and its beta-oxidized metabolite, phenylacetic mustard (PAM) were studied in plasma after the oral administration of 200 mg prednimustine (Sterecyt) and a regimen consisting of 20 mg prednisolone plus 20 mg chlorambucil, respectively. A total of 12 cancer patients completed this trial. The drugs were given in a cross-over study as single doses, and serial plasma samples were collected for 32 h. Chlorambucil and PAM were assayed by a gas chromatographic/mass spectrometry method and prednisolone, by radioimmunoassay. The median relative availability of the prednisolone and chlorambucil moiety in prednimustine was 19% and 16%, respectively. Prednisolone, as well as chlorambucil and PAM, appeared later and at a significantly lower concentration in plasma after treatment with prednimustine as compared with the mixture of chlorambucil and prednisolone. We also found that the elimination phase of chlorambucil and PAM in plasma is prolonged after the administration of prednimustine as compared with chlorambucil per se. In contrast, the elimination of the prednisolone moiety of prednimustine and that following the administration of a plain prednisolone tablet did not seem to differ. The modified plasma profile of the alkylating components following prednimustine administration may be important for the clinical efficacy of prednimustine.

Adult↗
PubMed1985

Vascular effects of phenylpropanolamine on human nasal mucosa.

The duration of the decongestant effect of phenylpropanolamine 2.5% as nose drops as well as the effect of the drug on nasal mucosal blood flow was studied in man. The nasal patency was significantly improved for up to three hours in patients with nasal congestion, while no effect on nasal mucosal blood flow was achieved. These results were discussed in relation to other more long-lasting nose-drops with blood flow-reducing effects.

Adolescent↗
PubMed1979

[Impotence].

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Ejaculation↗
PubMed1977

Substrate-inhibiton by acetyl-CoA in the condensation reaction between oxaloacetate and acetyl-CoA catalyzed by citrate synthase from pig heart.

Deviations from Michealis-Menten kinetics in the pig-heart citrate synthase (citrate-oxaloacetate-lyase(pro-3S-CH2-COO-leads to acetyl-CoA), EC 4.1.3.7) system have been characterized and analyzed in view of the kinetic theory described in the preceding paper. The enzymic condensation reaction between acetyl-CoA and oxaloacetate is subject to substrate-inhibition by acetyl-CoA. This can be attributed to the formation of a productive enzyme-acetyl-CoA complex with a dissociation constant of 110 uM. The binding of acetyl-CoA to the enzyme decreases the on-velocity constant for oxaloacetate-binding from 4000 min-1- micrometer-1 to 1700 min-1-micrometer-1. The affinity of citrate synthase for oxaloacetate increase at least 20-fold on the binding of acetyl-CoA. The latter cooperativity effect can be attributed to a more than 45-fold decrease of the off-velocity constant for oxaloacetate-binding.

Acetyl Coenzyme A↗