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Biomedical subjects

K H Frömming

Publications and source records attributed to K H Frömming.

At least 19 recordsLinked to original sources
PubMed1998

Development of computerised procedures for the characterization of the tableting properties with eccentric machines. High precision displacement instrumentation for eccentric tablet machines.

The paper deals with the instrumentation of displacement on an eccentric machine. Two instrumentation variants are evaluated. A displacement instrumentation consisting of two transducers attached to the frame was corrected for a slight non-linear calibration curve and corrected for machine deformation. A powder height signal was calculated from both signals. Upon dynamic punch to punch compression the powder height signal showed an oscillation of +/- 17 microns in amplitude due to tilting of the upper punch holder. A newly developed direct powder height instrumentation consisting of a set of special punches and a special die was also corrected for nonlinearities and punch deformation. The signal was free from any tilting effects and its accuracy is in the order of magnitude of the surface roughness of the punches. The machine deformation is discussed in detail. The instrumentation of the frame of the eccentric press in terms of force is possible but less sensitive by a factor of 5.4 than the use of the force sensors. The total machine deformation reaches nearly 0.5 mm under maximum load which is more than is often expected. The deformation was found to be non-linear for about 2% of the total deformation, the remaining 98% are linear deformation.

Chemistry, Pharmaceutical↗
PubMed1995

Penetration of hydrocortisone into excised human skin under the influence of cyclodextrins.

Hydrocortisone (HC) penetration into excised human skin from 1% (w/w) HC containing formulations with white petrolatum, an o/w cream and an aqueous polyacrylate gel is described. The experiments were performed with pure HC and the inclusion compounds with beta-cyclodextrin and hydroxypropyl-beta-cyclodextrin. The smallest HC amounts in the skin were found with the petrolatum preparations. No differences between the incorporation of free HC and the inclusion compounds was found. The highest HC amounts in the skin are found with the o/w cream and hydrogel formulation containing nonincluded HC. Incorporation of both inclusion compounds into these vehicles diminishes the HC concentration in the upper skin layers but not in the dermis. It is assumed that the preferred penetration route for the easily soluble inclusion compounds is a transappendageal diffusion rather than a transdermal one. A comparison with release results by using an ointment liberation model gives a good correlation with the penetration results in the dermis but not in the other skin layers.

Administration, Topical↗
PubMed1984

Verapamil disposition and effect on PQ-intervals after buccal, oral and intravenous administration.

The absorption, pharmacokinetics and effect on PQ-intervals of verapamil (Isoptin) administered as buccal tablet (20 mg), oral capsule (80-120 mg) and as an intravenous injection (5 mg) have been determined in 7 healthy subjects. Hysteresis plots of the percentage change in PQ-interval and serum concentration indicate that the efficacy of verapamil after buccal and intravenous application, as in earlier findings with sublingual verapamil tablets, was higher than after oral application. Thus the serum concentration-response curve after oral application is displaced towards the right reflecting lower potency. This phenomenon has been attributed by other workers to a stereospecific metabolism of the more active L-isomer during first pass through the liver, but competition at the receptor with metabolites cannot yet be ruled out. The rate of absorption, T1/2(alpha), terminal elimination half-life T1/2(gamma), and tmax of the buccal tablet was not significantly different from the oral capsule. The absolute bioavailability of the buccal preparation (37%) was slightly greater than the oral capsule (33%) and both had higher bioavailability than observed in earlier studies on verapamil dragees (10-20%). Thus, although the buccal tablet was alkalinised and had a rapid disintegration in vitro, characteristics thought to increase buccal uptake, the bioavailability is still much less then 100%.

Absorption↗
PubMed1983

[Release, absorption and elimination of theophylline from fast and slowly released oral formulations].

Each 2 tablets of four tablet formulations with 150 mg theophylline were administered to 6 and 5 volunteers, respectively, as single oral dose. 8 volunteers received 256 mg theophylline as a solution and as a sustained released formulation, as well as 176 mg theophylline as short intravenous bolus infusion. The elimination was independent of the examined formulations, but differences occurred between the experiments with the different groups of volunteers. The invasion parameters (t1/2i) of the four fast released tablet formulations corresponded to the values (t1/2a) of the oral theophylline solution. Furthermore, no difference existed concerning the mean times (Tsys). The mean time (theophylline) for the body model, Tvss, is 9.9 h; the mean time, which is attributed to the absorption process (Tabs) is 0.7 h; the mean in vivo dissolution time (Tdiss-vivo) for the sustained release formulation is 6.3 h. The mean time after oral administration of the theophylline solution (Tbiol) is 10.6 h. General conditions for a comparison between the in vitro and the in vivo release data are reported.

Administration, Oral↗
PubMed1982

[Pharmacokinetics and pharmacodynamics of verapamil in healthy volunteers after single oral and sublingual administration].

5-[3,4-Dimethoxyphenethyl)-methylamino]-2-(3,4-dimethoxyphenyl)-2- isopropylvaleronitril (verapamil, Isoptin) was administered p.o. (80 mg) and via the sublingual route (20 mg as the hydrochloride) in 6 healthy volunteers. After p.o. administration the mean peak serum concentration of 125.6 ng/ml was attained on average 80 min later. The half-life for the distribution phase (t1/2a) was 0.95 h and for the elimination phase (t1/2 beta) 6.08 h. After sublingual administration the mean peak serum concentration of verapamil was 26 ng/ml attained on average after 71.7 min. The mean t1/2a was 0.73 h and the mean T1/2 beta 4.39 h. There was an 18.4 min delay after oral administration and 0.8 min delay after sublingual administration before verapamil was detected in the serum. The relative bioavailability of verapamil sublingually was 2.7 (p.o. = 1.0). There were close correlations between the verapamil concentration in serum and the prolongation of the PQ-interval (0.725 sublingually; 0.853 p.o.). Approximately three times higher concentrations of verapamil were required when given by the oral route to produce the same prolongation of the PQ-interval obtained with sublingual administration. The variability of several important pharmacokinetic parameters of verapamil was reduced by sublingual application in comparison to the oral route. The coefficient of variation for the peak concentration, time to peak and t1/2 beta were 49.7%, 25.0% and 26.4%, respectively, after sublingual administration in comparison to 120.6%, 54.7% and 68.9%, respectively, when given p.o.

Administration, Oral↗
PubMed1981

Sorption properties of cross-linked insoluble polyvinylpyrrolidone.

The interaction of 32 drugs of diverse chemical structure with cross-linked insoluble polyvinylpyrrolidone (crospovidone) was studied. By using a polymer to drug ratio of 10:1, the sorbed amount for 20 compounds was found to be less than 5%. After a 10-fold decrease of the polymer concentration, the sorbed amount of eight other compounds fell to or below the 5% level. Only tannic acid and hexylresorcinol exhibited a significantly stronger sorption tendency. The interaction appeared to be controlled by phenolic groups in the active ingredient. The binding can be quantified by an interaction constant Ks, whose definition is based on a bulk phase model of interaction via independent binding sites. The exceptionally strong binding of hexylresorcinol, however, apparently was caused by cooperative interacting of the hexyl groups in the bound state. Desorption studies revealed that the binding was fully reversible in all cases. Therefore, the presence of cross-linked polyvinylpyrrolidone as a disintegrant in pharmaceutical preparations is not expected to interfere with GI drug absorption.

Adsorption↗
PubMed1981

[Change of relative bioavailability of riboflavin by the fluid intake (author's transl)].

Administration of 6,7-dimethyl-9-(D-1-ribityl)-isoalloxazine (riboflavin) solution (30 mg/200 ml) dissolved in a fruit juice to 5 volunteers resulted in increased relative bioavailability between 156 and 246% compared to the intake with water. The reason should be the delayed gastric emptying rate due to the osmotic pressure and the acidity of the juice.

Adult↗
PubMed1975

[Influence of ethanol on the in vitro and in vivo drug release from some sustained release tablets (author's transl)].

The in vitro and in vivo liberation of acetylsalicylic acid from sustained release tablets in presence of ethanol is described. Simultaneous uptake of 120 ml commercial brandy resulted in a faster release of the active substance from the tablets prepared with Eudragit ret-l (PM), as has been proved by urinary excretion data. These results were supported by experiments with a pH-endoaradio transmitter and by radiography.

Adult↗