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Biomedical subjects

V Saano

Publications and source records attributed to V Saano.

At least 55 records · Page 3Linked to original sources
PubMed1990

The effects of vadocaine, dextromethorphan, diphenhydramine and hydroxyzine on the ciliary beat frequency in rats in vitro.

Mucociliary function is a major cleansing mechanism of the respiratory tract. Many drugs used in the treatment of respiratory diseases impair the ciliary beat frequency (CBF) of mucous membrane. Our aim was to study by means of a photoelectric technique, the effects of two antitussives--dextromethorphan and vadocaine--and two antihistamines--hydroxyzine and diphenhydramine--on the rat tracheal CBF in vitro. The CBF was measured from tracheal explants immersed in drug solutions. Dextromethorphan (1.0 mg/ml and 10.0 mg/ml) caused 16.9-20.8% decrease in the CBF during the 40 min. measurement period. Vadocaine (0.1 mg/ml and 0.5 mg/ml) decreased the CBF by 6.9%. Higher vadocaine concentrations caused a dose-dependent inhibitory effect so that mucociliary function stopped totally within 20 min. with 5.0 mg/ml vadocaine solution. Both diphenhydramine and hydroxyzine totally stopped the ciliary activity during 20 min. with concentrations of 2.5 mg/ml and 1.0 mg/ml. respectively. Locke-Ringer solution used as a control did not cause any change in the CBF. These results suggest that the antihistamines diphenhydramine and hydroxyzine are more ciliostatic than the antitussives dextromethorphan and vadocaine on the rat tracheal cilia in vitro. The results suggest further in vivo studies. The used photoelectric detection method proved to be suitable for evaluating drug effects on the CBF of respiratory mucosa.

Animals↗
PubMed1990

Bioavailability of doxycycline from dissolved doxycycline hydrochloride tablets--comparison to solid form hydrochloride tablets and dissolved monohydrate tablets.

Doxycycline (DC) is used either as solid form hydrochloride capsules, or as monohydrate tablets, which may be taken either as solid form tablets or dissolved in water. In this single dose (150 mg), crossover study on 15 healthy volunteers, the pharmacokinetic properties of DC from hydrochloride tablets taken either in dissolved or in solid form were compared with those observed after taking dissolved DC as a monohydrate tablet. The results of this study show that DC is absorbed rapidly (tmax 3.3-3.8 h) and with equal bioavailability (AUC values 52.9-58.5 mg/l x h) from both hydrochloride and monohydrate tablets. It can be concluded that taking the DC hydrochloride tablets in dissolved form does not affect the pharmacokinetics of DC, moreover the bioavailability of DC is comparable to that achieved after taking DC monohydrate tablets in dissolved form.

Biological Availability↗
PubMed1990

Effect of central muscle relaxants on single-dose pharmacokinetics of peroral paracetamol in man.

Paracetamol (acetaminophen) at a single, 160-450 mg dose was given perorally in combination with central muscle relaxants (CMRs) carisoprodol (200 mg), chlormezanone (100 mg) or orphenadrine (35 mg) in a double-blind, randomized, cross-over study in 10 healthy volunteers. The pharmacokinetic parameters of paracetamol remained unaltered in the presence of the CMRs as compared with those observed after paracetamol without additives, in spite of nearly twenty-fold differences in the dissolution rate between the products. Paracetamol is absorbed mostly in the duodenum, and therefore there is enough time for even the slowly dissolving tablets to release the active principle before the gastric contents are transferred to the area of paracetamol absorption. Some CMRs are anticholinergic compounds and may affect intestinal motility. Our results show, however, that CMRs do not significantly alter the pharmacokinetics of paracetamol, and presumably the antipyretic or analgetic efficacy of paracetamol is not impaired when combination formulations of paracetamol and CMRs are used.

Acetaminophen↗
PubMed1990

Pharmacokinetics of ibuprofen in man: a single-dose comparison of two over-the-counter, 200 mg preparations.

The pharmacokinetic properties of two 200 mg, over-the-counter (OTC) ibuprofen preparations were compared in a randomized crossover study on ten healthy volunteers. After 2 times 200 mg single dose, one preparation produced peak plasma ibuprofen concentration 30.0 +/- 2.1 micrograms/ml at 1.6 h and the other preparation 23.2 +/- 1.9 micrograms/ml at 2.3 h (p less than 0.05). There was no statistically significant difference between the preparations in the bioavailability of ibuprofen. OTC ibuprofen preparations are mainly used for acute indications, such as fever or headache. In these cases, rapid absorption and high concentrations of active ingredient are desirable properties, especially when the amount of drug is relatively low. Therefore, the pharmacokinetic differences between these preparations may be therapeutically significant.

Adult↗
PubMed1989

Pharmacokinetics and acute side-effects of nifedipine given as slow-release tablets or liquid-filled capsules.

The pharmacokinetics and acute adverse effects of nifedipine were studied in a cross-over, single dose (20 mg) study on ten healthy young volunteers. From the liquid-filled capsules, nifedipine was absorbed rapidly (tmax at 30-40 min). From tablets, the peak concentration was 79-88% lower and occurred 74-133 min after ingestion; also the bioavailability was lower, as indicated by on average 39% lower area under curve values after tablets. All the volunteers experienced side-effects: the most common (nine out of the ten) and the most intense was headache. One volunteer withdrew because of unbearable vomiting and headache. Also others felt nauseous (six out of nine who continued) and four of them vomited. After tablets, the dizziness was markedly less than after capsules, but the more slowly-appearing symptoms such as headache and nausea were similar after both types of drug products. By using slow-release tablets instead of capsules it seems possible to avoid some side-effects of nifedipine, but this benefit is gained at the expense of bioavailability.

Adult↗
PubMed1988

Characterization of the selectivity, specificity and potency of medetomidine as an alpha 2-adrenoceptor agonist.

Medetomidine (4-[1-(2,3-dimethylphenyl)ethyl]-1H-imidazole) was tested for alpha 2-adrenoceptor agonist activity and compared to several reference agents. In binding studies carried out with rat brain membrane preparations, medetomidine showed high affinity for alpha 2-adrenoceptors, as measured by the displacement of [3H]clonidine (Ki 1.08 nM compared to 1.62, 3.20, 6.22 and 194 nM for detomidine, clonidine, UK 14,304 and xylazine, respectively). The affinity of medetomidine for alpha 1-adrenoceptors, as measured by [3H]prazosin displacement, was much weaker, yielding a relative alpha 2/alpha 1 selectivity ratio of 1620 which is 5-10 times higher than that of the reference compounds. Medetomidine caused a concentration-dependent inhibition of the twitch response in electrically stimulated mouse vas deferens with a pD2 value of 9.0 compared to that of 8.6, 8.5, 8.2 and 7.1 for detomidine, clonidine, UK 14,304 and xylazine, respectively. The effect of medetomidine was antagonized by idazoxan. In anaesthetized rats, medetomidine caused a dose-dependent mydriasis which could be reversed by alpha 2-adrenoceptor blockade. In receptor binding experiments and isolated organs medetomidine had no affinity or effects on beta 1-, beta 2-, H1, H2, 5-HT1, 5-HT2, muscarine, dopamine, tryptamine, GABA, opiate and benzodiazepine receptors. Based on these results, medetomidine can be classified as a potent, selective and specific alpha 2-adrenoceptor agonist.

Adrenergic alpha-Agonists↗
PubMed1988

Central-type and peripheral-type benzodiazepine receptors.

The benzodiazepines had already been in wide use as anxiolytics and anticonvulsants for more than ten years before their site of action in the central nervous system, the benzodiazepine receptor, was discovered. Simultaneously, a binding site in the peripheral organs, e.g. heart, lungs and kidneys, was found. Although some benzodiazepines, such as diazepam, bind to both central and peripheral benzodiazepine receptors with a high affinity, these two binding sites exhibit quite different properties. It is already clear that the central benzodiazepine receptors are in many regions of the brain coupled with the receptors for gamma-amino butyric acid, and they mediate the acute actions of benzodiazepines in the central nervous system. Through them opposite effects, such as anxiety and convulsions, can also be evoked by using inverse agonists, e.g. some beta-carbolines. All these effects can be blocked with benzodiazepine receptor antagonists, some of which are already used as specific antidotes against benzodiazepine overdose. The multitude of pharmacological effects that can be produced through central benzodiazepine receptors provides a good opportunity for the development of new drugs. The role of the peripheral-type receptors is less clear, but it seems that they are connected with more slowly-appearing drug actions, such as modulation of cell proliferation. Now that endogenous ligands for both the central-type (a peptide called diazepam binding inhibitor; DBI) and for the peripheral-type (porphyrins) benzodiazepine receptors have been discovered, even more productive research can be expected.

Animals↗
PubMed1987

Tremorigenic effect and inhibition of tryptamine and serotonin receptor binding by beta-carbolines.

The abilities of some naturally occurring beta-carbolines (BCs), dihydro-BCs and tetrahydro-BCs to inhibit the specific binding of 3H-tryptamine (TA), 3H-serotonin (5-HT) and 3H-ketanserine to rat brain membranes and to induce tremor in mice were studied. These compounds, particularly DHBCs and BCs, showed higher affinity for TA binding sites than to 5-HT1 or 5-HT2 binding sites inhibiting the former at nanomolar and the two latter ones at micromolar or high micromolar concentrations. The Ki values for norharmane, harmaline and harmine (17, 18 and 74 nM, respectively) for TA sites indicate the highest affinity so far described for natural beta-carbolines to any receptor sites and thus may indicate their major site of action. among the BC derivatives studied, the before mentioned harmala alkaloids were the most potent inducers of tremor in mice, although the orders of the tremorogenic potency and the binding to TA site did not correlate. It is suggested that especially the tremorigenic effect of BC derivatives is partly based on the binding to specific tryptamine receptors.

Animals↗
PubMed1987

Effect of anticonvulsant drugs on (35S)t-butylbicyclophosphorothionate binding in vitro and ex vivo.

Using several concentrations of eight anticonvulsant drugs in clinical use (carbamazepine, clonazepam, phenytoin, phenobarbital, ethosuximide, primidone, sodium valproate, and D,L-gamma-vinyl GABA), we studied their abilities in vitro to displace (35S)t-butylbicyclophosphorothionate (35S-TBPS) from its binding site in a homogenate of rat brain. Thereafter ethosuximide (150 mg/kg), phenobarbital (30 mg/kg), clonazepam (0.3 mg/kg), or phenytoin (100 mg/kg) was injected intraperitoneally into rats for 16-20 days; and the effect of drug administration on 35S-TBPS binding was studied in the cortex and hippocampus ex vivo. Phenobarbital (100 microM, P less than 0.001), ethosuximide (500 microM, P less than 0.001), and phenytoin (40 microM, P less than 0.001) decreased the specific 35S-TBPS binding in vitro by 10-16%. After drug administration of phenobarbital (concentration in plasma 168 microM), the number of binding sites decreased and the binding affinity (P less than 0.05) in the cortex increased. Other anticonvulsants did not modulate 35S-TBPS binding in vitro at the concentration analogous to therapeutic plasma levels or ex vivo at the dose used. These results suggest that the use of phenobarbital may modulate the TBPS binding site, but the role of the present findings in the anticonvulsant action of phenobarbital needs to be further studied.

Animals↗
PubMed1987

GABA-benzodiazepine receptor complex and drug actions.

This short review describes the benzodiazepine receptors, their interplay with GABAergic transmission and chloride ionophore, the search for endogenous ligands, and the drug responses that can be evoked through these receptors. Benzodiazepine receptors offer a unique pathway through which opposite drug actions e.g., anxiogenic and anxiolytic effects can be exerted, and these actions can be inhibited with competitive receptor antagonists. The most plausible endogenous ligand for benzodiazepine receptors discovered so far, a polypeptide DBI, exerts actions opposite to those of the benzodiazepines used in clinical therapy. This has been the stimulus for a new look at the physiological role for these receptors.

Animals↗
PubMed1986

Effects of diazepam, tofizopam or phenytoin during foetal development on subsequent behaviour and benzodiazepine receptor characteristics in rats.

The development of rats was studied for 3 postnatal weeks after prenatal medication with diazepam (10 mg/kg/day), phenytoin (50 mg/kg/day), or tofizopam (50 mg/kg twice daily) given by gastric intubation from day 7 to 21 of pregnancy. The treatments had no effect on the litter size. There were also no differences between the groups in a battery of tests for development (negative geotaxis, righting reflex, cliff avoidance, rotarod, passive avoidance), but the activity spurt seen at postnatal days 18-21 was missing in pups of diazepam-treated mothers. The number of benzodiazepine receptors and their affinity for tritiated flunitrazepam developed similarly in all of the rat groups. Thus, the transient changes in motor development seen 2-3 weeks after birth of rats whose mothers received diazepam during pregnancy do not seem to be related to changes in ontogenesis of benzodiazepine receptors.

Animals↗
PubMed1986

Indoloquinolizidines, formal derivatives of tetrahydro-beta-carbolines, show selective affinity for benzodiazepine, tryptamine and serotonin binding sites in rat brain.

Beta-carbolines and indoloquinolizidines occur in plants, and some of the former compounds also in mammalian tissues. Many beta-carbolines cause tremor or convulsions, and they are among the most potent known endogenous compounds to bind to benzodiazepine, tryptamine and serotonin binding sites. In this study seven indoloquinolizidines which are formal derivatives of 1,2-disubstituted 1,2,3,4-tetrahydro-beta-carbolines were assayed for their affinity for benzodiazepine, tryptamine and serotonin binding sites in rat brain in vitro. Three of them exhibited significant affinity for tryptamine receptors: Ki values ranged from 0.97 microM upwards. The affinity spectra towards different receptors greatly varied from compound to compound showing selectivity to one or several of the binding sites now studied. These derivatives of beta-carbolines may be useful tools when assessing the physiological functions of the tryptamine and other binding sites.

Animals↗
PubMed1986

Affinity of various compounds for benzodiazepine binding sites in rat brain, heart and kidneys in vitro.

Binding of several psychoactive, antiinflammatory, antihypertensive, and antiarrhythmic drugs to central and peripheral benzodiazepine (BZ) binding sites was studied in the brain, heart and kidneys of rats. Diazepam exhibited the highest affinity for all binding sites (Ki values at 0.01 microM level); another 1,4-BZ, oxazepam, had markedly lower affinity for peripheral binding sites (Ki 21-37 microM). Non-BZ compounds had low affinity for central BZ receptors; proquazone was the most potent (Ki 9.5 microM). The affinities of non-BZ compounds were higher for peripheral BZ binding sites. The Ki value for proquazone was approximately 0.1 microM; and many other antiinflammatory agents, and the vasodilators cyclandelate and nifedipine, produced Ki values in the micromolar level. beta-Blocking drugs, and several other antihypertensive and antiarrhythmic agents lacked affinity for both central and peripheral BZ binding sites. According to the results, the affinity for peripheral binding sites is independent of an affinity for central BZ receptors. Non-BZ compounds that bound to brain BZ receptors bound with equal affinity to both BZ1 and BZ2 subgroups of receptors. The compounds with affinity for peripheral BZ binding sites did not select between heart and kidneys, which suggests that these organs have similar binding sites. The role of the peripheral BZ binding sites has not yet been established. The findings of this study allow the selection of a more varied group of ligands to be used when investigating the physiological significance of these binding sites.

Animals↗
PubMed1986

Tofizopam selectively increases the action of anticonvulsants.

The effect of tofizopam, a 3,4-benzodiazepine (BZ) derivative, in modulating the anticonvulsive action of various drugs was investigated in mice. Electric shock and intravenous infusion of bicuculline were used as convulsive agents. Tofizopam increased the action of clonazepam, diazepam and flunitrazepam against bicuculline. The anticonvulsive effect of diazepam against electroshocks was augmented only slightly. Tofizopam failed to alter the actions of carbamazepine, phenobarbital, phenytoin, or sodium valproate against either of the convulsive stimuli. Both in vitro and in vivo, tofizopam has been shown to stimulate the binding of 1,4-BZs (e.g., flunitrazepam) to BZ receptors. Similarly, tofizopam enhances the binding of muscimol to GABA receptors. Although several anticonvulsants act on the GABA-BZ receptor complex, tofizopam seems to modify selectively the anticonvulsive action of 1,4-BZs, and this effect is seen better in bicuculline-induced seizures than in electroshocks.

Animals↗
PubMed1985

Night-time pharmacokinetics of once a day theophylline: a steady state comparison of three preparations.

We have carried out a steady state pharmacokinetic comparison of three different theophylline preparations in nine healthy volunteers using a once a day dosage schedule of 600 mg theophylline given before bedtime for four days. The preparations tested were Retafyllin 200 mg depot tablet (R), Theo-Dur 200 mg depot tablet (T) and Uniphyllin 200 mg tablet (U). All preparations in steady state reached the serum level of 8.9-10.2 microg/ml after a single evening dose of theophylline 600 mg. The pharmacokinetic profile of these slow release theophylline preparations was such that there is no risk of exceeding the therapeutic range even after a rather high evening dose. Individual variation was also observed in the present study but nobody exceeded the therapeutic range. The pharmacokinetic profiles of R and U were quite similar and they seemed to have suitable pharmacokinetic properties for once a day dosage, and they showed a more sustained action than T. Only minimal gastrointestinal side effects were reported during this study.

Adult↗
PubMed1984

Comparison of gas chromatography and receptor bioassay in the determination of diazepam in plasma after conventional tablets and controlled release capsules.

Plasma levels of diazepam and its metabolites were compared after a controlled release formulation and a regular tablet. Both gas chromatographic analysis of plasma diazepam and desmethyldiazepam and radioreceptor assay of total benzodiazepine activity were used. Also the concentrations of benzodiazepine in saliva samples were analyzed by radioreceptor assay. A typical initial plasma peak was seen after the regular tablet but not after the controlled release capsule. Hence the excessive initial sedation can be avoided and the risk of abuse reduced. Desmethyldiazepam increased for about two days after a single dose of diazepam. The receptor assay correlated in general with the sum of diazepam and its desmethyl derivative. The saliva assay gave about 2.5% of the plasma total benzodiazepine which correlates well with the expected free benzodiazepine. It seems that both the plasma radioreceptor assay and the saliva assay can be used to monitor the total benzodiazepine concentration.

Adult↗