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Biomedical subjects

R Oertel

Publications and source records attributed to R Oertel.

62 records · Page 4Linked to original sources
PubMed1987

[Diagnostic value of atrial natriuretic peptide in hypertension and heart insufficiency].

Serum ANP levels were measured by radioreceptor assay in 40 patients with various forms of secondary hypertension and 6 patients with heart failure. In addition, serum ANP was determined in 4 patients with renal artery stenosis before and after dilatation, as well as in 5 anephric patients before and after haemodialysis. Our results showed elevated serum ANP level in most patients with various forms of secondary hypertension and chronic heart failure. A distinction between these two groups and a control group of healthy individuals was not possible due to the wide range and occasional normal levels in the first two groups. ANP levels in patients with renal stenosis decreased after dilatation but there was no correlation with the success of this procedure. A positive correlation between ANP and plasma renin level was detectable in patients with renal artery stenosis, but was also elevated in anephric patients with absent renin production. In summary, our results show that measurements of serum-ANP are of little significance in the diagnosis of hypertension and chronic cardiac failure.

Atrial Natriuretic Factor↗
PubMed1986

Effect of bethanechol and metoclopramide on upper gastrointestinal motility in the kitten.

Gastroesophageal reflux (GER) during infancy is a disorder of unknown etiology which may be associated with abnormalities of upper gastrointestinal motor function. Bethanechol, a muscarinic agonist, and metoclopramide, a dopamine antagonist, have been utilized as pharmacologic agents in an attempt to improve upper gastrointestinal motility in this disorder. We have studied the effect of these agents on upper gastrointestinal motility in an infant model, the kitten. Bethanechol is found to greatly increase lower esophageal sphincter (LES) pressure and have no effect on esophageal peristaltic amplitude or gastric emptying of a liquid meal. Metoclopramide causes a small and nonsignificant increase in LES pressure, has no effect on esophageal peristalsis, and increases the rate of gastric emptying of a liquid meal. These results suggest that these two agents may have specific actions on the infant's upper gastrointestinal tract.

Animals↗
PubMedDate not supplied

Dose dependent tiracizine disposition in healthy volunteers: serum and urine kinetics and dose related ECG-changes.

The pharmacokinetics of tiracizine, a new class I antiarrhythmic agent, and 3 of its metabolites were assessed in serum and urine of 8 healthy extensive metabolisers after single oral administration of 50, 100, and 200 mg tiracizine hydrochloride. Additionally, tiracizine induced ECG-changes were compared between the different doses. With increasing doses enhancement of AUC and Cmax of tiracizine and its metabolites revealed a slight deviation from linearity indicated by exceeding the upper limits of the 95% nonparametric confidence interval set by 0.8-1.2 for the ratio (dose corrected parameters after the 100 and 200 mg dose, respectively)/(parameters after 50 mg). The increase of the dose corrected parameters after the 200 mg dose was about 1.3-fold compared with the 50 mg parameters for the parent compound as well as its metabolites. The significant decrease of the renal clearance of all 4 substances with increasing doses indicates that saturable tubular secretion mainly accounts for non-linearity. Due to the occurrence of non-linear (tubular secretion) as well as linear (glomerular filtration, hepatic metabolism) elimination in parallel, however, it is concluded that saturable tubular secretion is of minor importance at higher doses and should not be overestimated. However, there was some evidence for saturable hepatic tiracizine metabolism in 4 of the 8 participants. Therefore, a fall of apparent intrinsic clearance has also to be taken into consideration, especially at higher doses. PQ- and QRS-intervals were prolonged in a dose dependent manner and culminated at 1 h after drug intake. QTc-time, however, remained unchanged. A log-linear relationship between serum concentrations of the parent compound and PQ- as well as QRS-time is suspected for serum levels about 80 ng/ml, but has to be confirmed by individual pharmacokinetic-pharmacodynamic modelling. PQ- and QRS-intervals might be suitable for tiracizine therapeutic monitoring.

Adult↗
PubMedDate not supplied

The effect of age on pharmacokinetics of the local anesthetic drug articaine.

BACKGROUND AND OBJECTIVES: With increasing age, there are physiologic changes that could affect pharmacokinetics of drugs. More elderly patients are undergoing routine dental procedures for which local anesthesia could be required. The goal of the present study was to evaluate the effect of age on pharmacokinetics of the local anesthetic agent articaine. METHODS: The submucosal infiltration anesthesia from two different dosages of 4% articaine without epinephrine was compared in healthy elderly and young volunteers. High performance liquid chromatography has been used to determine concentrations of articaine in serum. Basic pharmacokinetic parameters were calculated according to standard procedures using a two-exponent equation. RESULTS: The clearance and volume of distribution (Vdss) of articaine after infiltration anesthesia were significantly lower in elderly volunteers compared with young volunteers. The area under the serum concentration-time curve and maximum drug concentration (Cmax) values did not differ significantly with age; however, both parameters tended to be higher in elderly volunteers. No changes in terminal half-life and time to reach maximum serum concentration (t(max)) were observed. The Cmax and tmax values of the metabolite articainic acid were similar in young and elderly volunteers. CONCLUSIONS The results show that the metabolism of articaine is age-independent in healthy male volunteers. The smaller Vdss in the elderly results in a trend to higher serum levels after a given dose of articaine. No change of dosage of articaine in elderly patients should be necessary.

Adult↗
PubMedDate not supplied

Saturable in vitro metabolism of articaine by serum esterases. Does it contribute to the persistence of the local anesthetic effect?

BACKGROUND AND OBJECTIVES: The amide-type local anesthetic articaine is unique in that hydrolysis to articainic acid by serum esterases is its main metabolic pathway. The purpose of the present investigation was to study the concentration dependence of this pathway in vitro. METHODS: To unbuffered (pH 8.2) as well as phosphate-buffered (pH 7.4) heated serum samples were added various amounts of articaine in the range 10-300 micrograms/mL. Concentrations of articaine and articainic acid were measured by high-performance liquid chromatography after incubating the samples at 37 degrees C for intervals ranging from 5 minutes to 6 hours after addition of articaine. RESULTS: The in vitro metabolism of articaine was shown to undergo pH-dependent Michaelis-Menten kinetics, indicating saturation at higher substrate concentrations. The Michaelis constant K(m) was determined as 175 micrograms/mL and 22.1 micrograms/mL and the maximum reaction rate Vmax as 2.1 micrograms/mL/min and 0.17 microgram/mL/min at pH 8.2 and pH 7.2, respectively. These results support previous in vivo observations that suggest saturable articaine metabolism, indicated by higher articaine/articainic acid metabolic ratio with higher articaine concentrations in alveolar blood after dental extraction. CONCLUSION: Local saturation of the serum esterases may contribute to the advantageous relationship between persistence of the local anesthetic effect and low systemic toxicity caused by the last systemic elimination of articaine (ie, its wide toxic therapeutic ratio).

Anesthetics, Local↗