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Biomedical subjects

P Rohdewald

Publications and source records attributed to P Rohdewald.

At least 55 records · Page 3Linked to original sources
PubMed1986

HPLC determination of glucocorticoid alcohols, their phosphates and hydrocortisone in aqueous solutions and biological fluids.

High-performance liquid chromatographic (HPLC) assays are described for the determination of dexamethasone phosphate, dexamethasone and hydrocortisone and for the determination of triamcinolone, triamcinolone acetonide, triamcinolone acetonide phosphate and hydrocortisone in aqueous solutions and biological fluids. These assays allow quantification of the glucocorticoids in plasma down to a concentration of 100 ng ml(-1) (dexamethasone phosphate 300 ng ml(-1), hydrocortisone 40 ng ml(-1)). During the development of optimum extraction procedures the pK(a) values of the esters were determined by extractions performed at different pH values. The stability in vitro of the phosphate esters in ampoules, plasma and blood was studied. The esters are stable in their formulated ampoules after long-term storage, whereas the half-life in vitro of dexamethasone phosphate in plasma at 37 degrees C is 5 h and that of triamcinolone acetonide phosphate is 3.5 h. Determination by HPLC of endogenous hydrocortisone in samples from patients who received either dexamethasone phosphate or triamcinolone acetonide phosphate gave results identical with those obtained by radio-immunoassay (RIA).

Journal Article↗
PubMed1986

Polyalkyl cyanoacrylate nanocapsules.

In-situ polymerized methyl cyanoacrylate (MCA), ethyl cyanoacrylate (ECA), and butyl cyanoacrylate (BCA) were used to prepare nanocapsules of fluorescein or doxorubicin as markers by a w/o emulsion interfacial polymerization technique. Different concentrations of MCA were also used to show the effect of monomer concentration. The nanocapsules were characterized by electron microscopy, particle size analysis, holding capacity and in-vitro release of the marker substances. After selection of the polymerization solvent system, nearly spherical nanocapsules were obtained using each of the monomers. Most of the nanocapsules prepared were in the particle size range 500-1500 nm diameter. They were able to hold 55-74% of the marker initially present in aqueous solution. In-vitro dissolution studies showed that release of marker was retarded variably in an increasing order from nanocapsules containing MCA, ECA then BCA. Increasing the concentration of the monomer in the nanocapsules led to retardation of marker release.

Capsules↗
PubMed1985

Pharmacokinetics of triamcinolone acetonide and its phosphate ester.

Triamcinolone acetonide in the form of its phosphate ester was given intravenously in two different doses (10 mg/kg and 80 mg). Plasma levels of the ester and triamcinolone acetonide were measured and pharmacokinetic parameters were calculated. The pharmacokinetics both of the phosphate and the free alcohol were dose-dependent. No unchanged ester was found in the urine, indicating complete conversion of the pro-drug. Triamcinolone was not a major metabolite of triamcinolone acetonide in humans. Renal clearance was low and independent of the dose. Only about 1% of the dose was found in the urine as triamcinolone acetonide.

Adult↗
PubMed1985

Simultaneous determination of glucocorticoid alcohols, their succinates and hydrocortisone in plasma.

A reversed-phase high-performance liquid chromatographic (HPLC) assay is described for the simultaneous determination of methylprednisolone, methylprednisolone-21-hemisuccinate and endogenous hydrocortisone in biological fluids. This assay is also applicable to the determination of prednisolone-21-hemisuccinate in the presence of prednisolone and hydrocortisone in biological fluids. Prednisolone and hydrocortisone are determined by normal-phase HPLC. The stability of hemisuccinate esters in ampoules, in saline and in plasma has been studied. Whereas the esters were stable in saline at 37 degrees C, they were considerably hydrolysed in plasma at the same temperature. Comparison of hydrocortisone levels obtained by HPLC and radioimmunoassay (RIA) showed the large influence of the cross-reactivity of methylprednisolone and hydrocortisone in the presence of high serum concentrations of methylprednisolone.

Journal Article↗
PubMed1985

Kinetics of methylprednisolone and its hemisuccinate ester.

Methylprednisolone in the form of its hemisuccinate ester was injected intravenously in doses of 10 mg/kg and 63.1 mg. Plasma levels of methylprednisolone and of the ester were measured and their kinetics were calculated. Results indicate dose dependency in the kinetics of both. About 10% of the dose was excreted unchanged as hemisuccinate in the urine, indicating incomplete conversion of the prodrug. When methylprednisolone (80 mg) was also taken by mouth, the relative bioavailability of the tablets was 99%. Saliva levels of methylprednisolone were low but paralleled plasma levels in the postdistribution phase. No methylprednisolone hemisuccinate was found in saliva.

Absorption↗
PubMed1985

Placebo-controlled study of the efficacy of topical antihistaminics against histamine-induced pruritus.

2 antipruritic ointments, when compared to placebo, were ineffective against histamine-induced itching applied in 2 volunteers after the intracutaneous injection of histamine. Testing of 11 topical antihistaminics after pretreatment for 30 and 60 min on 12 volunteers showed that some of the preparations reduced the histamine-induced itching significantly, while others were able to inhibit itching only slightly or were very close to placebo. Pain from pin pricks could not be attenuated significantly by pretreatment with the topical antihistaminics at any time.

Administration, Topical↗
PubMed1984

[Shock lung (ARDS): glucocorticoids?].

Numerous experimental investigations have demonstrated the benefit of glucocorticoids in the initial phase of the shocklung syndrome (ARDS), showing an increasing pulmonary perfusion by blocking the formation of vasoactive substances and a stabilization of endothelial and lysosomal membranes; another effect is to be seen in the inhibition of neutrophilic chemotaxis and pulmonary leukostasis, leading to reduced inflammatory reaction and less severe pulmonary damage. Clinical studies of glucocorticoid therapy in ARDS indicate a higher rate of surviving patients, when they were treated early and with glucocorticoids in a high dosage. The ill-defined condition of ARDS, however, and the use of different dosages in most of the studies limit the comparison of success dependent on those regimes; e.g. the given dosage varies from a single dose of 250 mg. methylprednisolone to several infusions of 30 mg./kg. body weight. According to the pharmacokinetics of glucocorticoids, the desired effects cannot be expected by application of a single and small dosage. To verify the benefit of high-dosage glucocorticoids in ARDS a stronger definition is needed to mark the onset of the syndrome and the start of glucocorticoid treatment. Additionally the dosage regimen should be standardised.

Adult↗
PubMed1983

Identification of glucocorticoid receptors in normal and neoplastic adult human lung.

A dexamethasone-binding protein was detected in cytosol of five normal and three neoplastic lung tissue samples. The apparent dissociation constant of the dexamethasone protein complex ranged from 5.8 to 21 nM (11.4 +/- 5.7 nM for normal tissue cytosol, 12.1 +/- 7.7 nM for the neoplastic tissue cytosol). The binding protein sedimented at 8 S in sucrose density gradient at low ionic strength and showed a high specificity for glucocorticoids. It was concluded that the dexamethasone-binding protein had the characteristics of a glucocorticoid receptor. The glucocorticoid receptor content was determined to be 12-77 fmol/mg protein (37.1 +/- 18.9 fmol/mg protein for the normal tissue cytosol, 51.9 +/- 23.9 fmol/mg protein for the neoplastic tissue cytosol).

Aged↗
PubMed1983

Relationship between saliva levels of metamizol metabolites, bioavailability and analgesic efficacy.

Salivary levels of the metabolites of metamizol (N-methyl-, N-acetyl- and 4-aminoantipyrine) were determined after the intake of film-coated metamizol (Novalgin) tablets and metamizol (Novalgin) solution. Cortical evoked potentials, pain ratings and thresholds of sensation were monitored following tooth pulp stimulation after administration of metamizol tablets. Within the different groups of subjects a remarkable degree of reproducibility was obtained for the metabolite concentrations in saliva. At 20 min after drug intake a more rapid absorption was demonstrable for the solution in comparison to the tablets. The metabolite levels were correlated to the simultaneously recorded pain response demonstrating that the analgesic efficacy can only be attributed to the two metabolites N-methyl- and -4-amino-antipyrine.

Adult↗
PubMed1982

Changes in cortical evoked potentials as correlates of the efficacy of weak analgesics.

The relationship between subjective measurements of pain (pain report and threshold of sensation) and evoked potentials following painful electrical stimulation of tooth pulp was evaluated after intake of different weak analgesics. These time-response curves for the dolorimetric parameters were correlated to the in vivo drug levels obtained in corresponding experiments by analyzing saliva. Based on the comparison between the drug levels of analgesics in saliva on the one hand and the threshold of sensation, the pain rating and changes in the amplitude of the cortical EP on the other hand, the sensitivity of the EP to changes in drug concentration was superior than to subjective pain judgement. The data were correlated to clinical pain relief investigations. The results support the suggestion of earlier research that EP evaluation may well serve as a correlate for laboratory pain.

Adult↗
PubMed1982

Cortical-evoked potentials and saliva levels as basis for the comparison of pure analgesics to analgesic combinations.

Cortical-evoked potentials, pain ratings and thresholds of sensation were monitored after tooth pulp stimulation under the influence of marketed mixtures of analgesics. Simultaneously the saliva levels of the individual pharmacological active components of these mixtures were measured by high-performance thin-layer chromatography. The action of the mild analgesics in the mixtures was calculated from the linear correlations of changes in cortical-evoked potential with saliva levels of the analgesics. The ineffectiveness of low doses of salicylamide in the combinations was demonstrated by this method. None of the investigated combination products was superior to the same doses of either acetylsalicylic acid, paracetamol or phenazone.

Adult↗
PubMed1981

Rapid thin-layer chromatography of various weak analgesics in saliva.

A thin-layer chromatographic method was developed to analyze phenacetin, 4-amino-phenazone and N-methyl-4-aminophenazone (5 and 1.25 micrograms/ml); bucetin (4-ethoxy-beta-hydroxybutyranilide), propyphenazone and N-acetyl-4-aminophenazone (2.5 and 1.25 micrograms/ml); phenazone (15 and 1.25 micrograms/ml); and N-acetylsalicylamide (0.25 micrograms/ml). The method was designed to study the bioavailability of different commercial tablets from salivary concentration data.

Analgesics↗