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Biomedical subjects

G Heimann

Publications and source records attributed to G Heimann.

At least 73 records · Page 4Linked to original sources
PubMed1983

[Pharmacokinetics of combined antibiotic therapy in the newborn infant].

In 66 newborn infants (AGA) suffering from septicemia concentration time courses of gentamicin, ampicillin and cefotaxim were determined to perform and an individual drug monitoring. Gentamicin was analysed from capillar blood samples using EMIT, Ampicillin and Cefotaxim by HPLC-technique. Volumes of distribution, apparent elimination half lives, maximum -, minimum and steady state concentrations were calculated using digital iteration programs. Based on a fixed dose regimen the kinetic parameters of gentamicin were extremely variable. To achieve a median steady state concentration of 3 micrograms/ml gentamicin in serum corrections from -17% to +110% of the foregoing dose were necessary. With 100 mg/kg ampicillin or cefotaxim per day sufficient concentrations in serum were reached. But in some patients a dosage of 5-7 mg/kg/d of gentamicin is too low, while others show concentrations near to the toxic levels. By a combination of gentamicin plus ampicillin pharmacokinetic parameters are not influenced; while if gentamicin is combined with cefotaxim the apparent elimination halflife of gentamicin (beta-slope) is significantly reduced. Therefore an individual drug monitoring of drugs with a small therapeutic range, for example gentamicin, is necessary to optimize therapeutic results.

Ampicillin↗
PubMed1983

Pharmacokinetics of antimicrobial drugs in the cerebrospinal fluid.

The physicochemical properties of the blood-to-brain barrier, the cerebrospinal fluid (CSF) to brain barrier, and the blood-CSF barrier, including their specific transport mechanisms, are responsible for drug concentration time courses in the CSF, which increase slower and remain lower than in the serum. From the kinetic point of view the central nervous system (CNS) can be understood as a deep compartment in the organism. During the initial inflammatory phase of a bacterial meningitis, the penetration of antibiotics can be increased. Consequently, sufficient CSF concentrations should be achieved as soon as possible. To investigate the influence of the dosage regimen on the kinetic profile of antibiotics in the CSF, chloramphenicol and cefotaxim were measured using high pressure liquid chromatography (HPLC)-techniques. Five children had a bacterial meningitis and five an external ventricular drainage due to various diseases. Neither continuous infusion over a 12-24-hour-period nor four bolus-injections per day led to sufficient antimicrobial concentrations within the first hours after starting therapy. Using a loading dose of 40-50% of the daily dose administered over a 2-4-hour infusion period and followed by bolus injections, sufficient concentrations of chloramphenicol and cefotaxim could be achieved within a few hours. Besides an adequate choice of antibiotics, the special pharmacokinetic properties of the cerebrospinal membranes should not be neglected in the concept of the antibiotic therapy of meningitis.

Bacterial Infections↗
PubMed1982

Influence of food intake on bioavailability of theophylline in premature infants.

16 premature infants suffering from neonatal apnoea received orally an aqueous solution of theophylline 5 mg/kg bodyweight under fasting conditions and immediately before a milk feed. Bioavailability up to 7 h after administration was determined from the serum concentration-time course. The rate of absorption was significantly decreased if the drug was given with food; mean maximum serum concentrations were reached after 4.7 h instead of 1.6 h under fasting conditions. The area under the curve did not differ between the two patient groups which indicates that only the rate but not the amount of absorption was affected by food intake. The influence of feeding on the rate of absorption of theophylline by premature infants, which is more pronounced than in adults, can be related to particular functional factors in the gastrointestinal tract during the neonatal period.

Apnea↗
PubMed1982

Disposition of the antiepileptic oxcarbazepine and its metabolites in healthy volunteers.

Oxcarbazepine (oxcarb) 600 and 900 mg (2360 and 3540 mumol) was taken by 3 volunteers (2 female, 1 male; 45-67 kg; age 22-34 years) after an overnight fast. Blood, saliva and urine were collected for the next 72 h for assay of oxcarb, 10,11-dihydro-10-hydroxy-carbamazepine (OHcarb), and 10,11-dihydro-trans-10,11-dihydroxy-carbamazepine (diol). Oxcarb reached a maximum level of about 1 microgram/ml (3.93 mumol/l) within 1 h and dropped below the detection limit (0.1 microgram/ml = 0.39 mumol/l) within 3 h. The active metabolite OHcarb appeared in the blood before oxcarb and reached the higher maximum level of 7.4 microgram/ml (29 mumol/l) after 7 h. Thereafter serum levels decreased with a t1/2 of about 25 h, and after 40 h with a t1/2 of 9 h, the latter agreeing with the renal excretory t1/2 calculated from the urine data (10 h). The ratio of OHcarb concentration in saliva to that in plasma varied considerably (0.3-1.7; median 1; r greater than 0.9), whereas that of blood to plasma was 1.25 with only small variation (r greater than 0.98); OHcarb concentrations in erythrocytes were 50% higher than in plasma. Diol was detected in blood (maximum level 0.5 microgram/ml = 1.84 mumol/l) in 2 volunteers. 45% of the dose could be recovered in urine (Oxcarb 5%, OH-carb 36%, Diol 4%). Whereas Oxcarb was completely conjugated, only 25% of OHcarb was conjugated and diol was unconjugated.

Adult↗
PubMed1981

[Kinetic parameters of D(+)-glucose in epileptic children and under anticonvulsive therapy (author's transl)].

In 17 Children 5-14 years old, suffering from recurrent convulsive disorders the kinetic parameters of D(+)-glucose were determined before and after treatment. 20 children treated with different anticonvulsants for many years were included in the study, 11 children served as control group. The elimination half-life of glucose is significantly shorter (1.5 plus or minus 5,4 min) before treatment. After sufficient drug therapy the elimination half-life becomes normal (19.6 plus or minus 4.9 min). The glucose pool which is decreased before treatment normalizes when drugs are given. During long term treatment the glucose transfer (metabolisation rate) is increased when convulsions occur or abnormalities of the EEG are observed. Neither the duration of the treatment nor the kind of drugs seem to influence the kinetic parameters of glucose.

Adolescent↗
PubMed1981

Drug disposition during the perinatal period.

During the perinatal period the problems of drug disposition are pronounced. The adaptation from the maternal-fetal unit to extrauterine life leads to alterations in drug absorption, distribution, metabolism, and renal elimination. Since both morphology and function of the alimentary tract changes, drugs are absorbed more slowly in the neonate than in older infants. Moreover, the serum protein binding of drugs is reduced in neonates. Consequently a measured plasma concentration may reflect a higher plasma/tissue level in the newborn as compared with adults. If the distribution volume of a drug corresponds to the total body water or extracellular water space, the dosage may be calculated in relation to the individual variations in the body surface area. But this procedure is not applicable for the newborn infant due to impaired metabolic functions of the liver and renal elimination mechanisms. The capacity of drug oxidation and glucuronidation is not fully developed in the neonate. Also glomerular filtration and tubular secretion are reduced during the first weeks of life. Therefore the elimination half-lives of many drugs are considerably prolonged in the newborn compared with that in older infants. As a consequence, individual therapeutic drug monitoring based on pharmacokinetic concepts and assisted by computer programs is becoming increasingly important.

Blood Proteins↗
PubMed1980

[Bioavailability of monofluoride preparations for dental caries prophylaxis (author's transl)].

Three different preparations containing 1 mg fluoride were given to 12 volunteers: preparation A, 1 hydrous solution, = 1 mg F-/100 ml, preparation B = 2 tablets at 0.5 mg F- and preparation C = 1NaF tablet with 1 mg F-. Representactive kinetic data could be obtained by means of restricted fluoride in the diet, a reproducible method yielding minimum detectable fluoride concentration and selection of suitable volunteers.. The enteral absorption of fluoride from solution A was more rapid (half-life of invasion = 20.2 min and 16.9 min, respectively). The delayed release is a consequence of the galenic mixture. In addition, the maximum concentration in plasma was greater and was reached sooner in preparation A when compared to the other preparations. In contrast, there was no difference in the areas under the curves, indicating that the relative bioavailability of fluoride is the same in all preparations.

Adult↗
PubMed1979

[Influence of dental caries prophylaxis using fluor-vigantoletten 1000 on plasma fluoride levels in infants (author's transl)].

A group of 57 newborns was divided into two: group I (27 subjects) received solely 1,000 I.U. vitamin D3 per day for 6 months, whereas group II (30 subjects) were given a combination of 1,000 I.U. vitamin D3 and 0.25 mg fluoride. At the end of the time of observation there was a significant difference between the plasma concentrations in the two groups. The median value was 13.06 microgram/l (range: 8:18-39.4 microgram/l) in group I and 16.54 microgram/l (range: 9.9--41.2 microgram/l) in group II. Fluoride is obviously available to infants when administered in combination with Vitamin D3. In addition, it could be proven, that after 6 month administration of fluoride there are no signs of cumulation, overdosage or even intoxication.

Cholecalciferol↗
PubMed1979

[Pharmacokinetics of Azlocillin in premature and newborn infants (author's transl)].

In 13 newborns and 12 prematures the pharmacokinetic parameters of 6-[(R)-2-(2-oxo-imidazolidine-1-carboxamido)-2-phenyl-acetamido]-penicillanic acid sodium salt (azlocillin, Securopen), were investigated after a single i.v. load of 50 mg/kg body weight. From the concentration-time curve an open two-compartment model could be postulated. The values of the microconstants indicate that there is a rapid diffusion from the peripheral compartment into the central one. The elimination half-life calculated from the beta-slope is 2.6-2.5 h. differences between newborns and prematures are lacking. To reach an average steady-state concentration C-infinity between 50 and 80 microgram/ml plasma, 100-200 mg azlocillin/kg body weight during 24h must be given. The accumulation rates for a dosage interval of 6 or 8 h are 0.6 and 0.45.

Azlocillin↗
PubMed1978

[Clinical course of congenital toxoplasmosis in dicygotic twins (author's transl)].

The presented case report deals with the clinical course of a congenital toxoplasmosis in dicygotic twins. The variability of the clinical course was proofed, because one of the twins remained unaffected with clinical signs and was detected only by the conversion of the seroreactions. On the other hand the second twin showed the picture of an acute meningoencephalitis resulting in a neurological defect syndrome. The reasons for the different clinical course, which is more pronounced in dicygotic twins than monocygotic, remain unknown.

Diseases in Twins↗
PubMed1978

[Enteral absorption of sulfasomidine depending on age (author's transl)].

After intravenous and oral application of 25 mg 6-(sulfanilamido)-2,4-dimethyl-pyrimidine (sulfasomidin)/kg body-weight to 29 newborns, 8 infants and 9 older children the completeness and rate of absorption were determined. Sulfasomidine was completely absorbed in newborns (mean value 95.7%) as well as in older children (mean value 94.4%). Concerning the rate of absorption there were age-dependent differences. Using the Bateman function for the kinetic model of intestinal absorption the rate constant of invasion k1 was significantly lower in the first week of life compared to that in older children. In agreement with these data the time tmax of the maximum serum concentration was significantly prolonged in newborns compared to that of older children.

Administration, Oral↗
PubMed1978

[Rectal absorption of phenobarbital in children as affected by different vehicles].

68 infants received 7--15 mg phenobarbital and sodium-phenobarbital/kg body weight by suppositories of different melting-points and hydroxyl-values (Witepsol H 12, W 35, E 76). The kinetic analysis of the serum concentration curve shows that the rate of rectal absorption is significantly increased if sodium-phenobarbital instead of phenobarbital is applied. The absorption rate is faster using suppositories with a lower melting-point (32.5 degrees C) compared to suppositories with a higher one (37.5 degrees C). Increasing the amount of hydroxyl values in the vehicle the absorption rate of phenobarbital becomes faster. Comparing the area under the serum concentration curve after intravenous and rectal application in 8 infants the absorption ratio was 74%.

Chemical Phenomena↗
PubMed1977

Pharmacokinetics of phenobarbital in childhood.

In 14 neonates 1-4 weeks old, 30 babies aged 1-12 months, and 7 infants of 1-5 years of age, the serum levels of phenobarbital were determined by a gas chromatographic micro-method after intravenous injection of phenobarbital 5-10 mg per kg body weight. It was possible to calculate the pharmacokinetic parameters using a two compartment open model. The distribution volumes within the individual age groups and the rate constants k12 and k21 showed no significant differences, but the elimination half-life was significantly longer in neonates (118.6+/-16.1h) than in babies (62.9+/-5.2h) or infants (68.5+/-3.2h).

Child, Preschool↗