Small-intestinal transfer mechanism of prunasin, the primary metabolite of the cyanogenic glycoside amygdalin.

1. The small-intestinal transfer of prunasin (D-mandelo-nitrile-beta-D-glucoside), the primary metabolite of amygdalin which is not absorbed in the small intestine as such, was studied in rat jejunum and ileum in vitro. 2. As shown by high pressure liquid chromatography, prunasin is transferred essentially intact across the intestinal wall, without cleavage of the glycosidic bond and thus no formation of benzaldehyde or cyanide during the mucosal passage. 3. Only the jejunal transfer of prunasin followed saturation kinetics (vmax = 1.6 mumol cm-1 min-1; KT = 460 mumol l-1) and exhibited a clearsodium-ion dependence. As indicated by the temperature dependence, only the jejunal mucosa-to-serosa transfer and the corresponding tissue uptake of prunasin required apparently high activation energies. Transfer in the terminal ileum showed diffusion characteristics. 4. Jejunal methyl alpha-D-glucoside transfer was inhibited by the presence of prunasin. Furthermore, the tissue uptake of methyl alpha-D-glucoside in rat jejunum was competitively inhibited by prunasin. 5. The results indicate that prunasin is absorbed unmetabolised in the jejunum of the rat via the transport system of glucose.

Rabbit model for estimating relative bioavailability, residues and tissue tolerance of intramuscular products: comparison of two ampicillin products.

A rabbit model for simultaneous investigation of the bioavailability, tissue residues and tissue tolerance of intramuscularly administered veterinary medicines is described. The bioavailability of ampicillin from two intramuscular products, which had been found to be different in calves, were compared in a two-way crossover design. The ampicillin levels in plasma, ampicillin residues in tissues, the plasma creatine kinase activity and the tissue damage at the injection sites were studied. The absolute bioavailabilities for the products were 100% and 40%. Differences in pharmacokinetics of ampicillin between sexes were observed after intravenous and intramuscular administration. Only slight tissue damage could be detected at the injection sites after intramuscular administration of these products. The results were compared with those obtained previously in calves and were found to be similar. Further investigations with other intramuscular drug products to validate this model are under way.

The bioavailability of diclofenac from enteric coated products in healthy volunteers with normal and artificially decreased gastric acidity.

The relative bioavailability of four monolithic enteric coated (MEC) diclofenac products was compared in 16 healthy volunteers. Only one generic product was fully bioequivalent with the reference product Voltaren with regard to AUC, Cmax, and tlag. Two products showed significant differences in tlag. In a second experiment with eight volunteers the influence of increased gastric pH (ranitidine treatment) on the two mutually most differing products was studied. They showed equivalence in AUC, but not in Cmax. Analysis of tlag suggests that the product with the low tlag disintegrates within the non-acid stomach, whereas the product with the long tlag passes the non-acid stomach intact. Several in vitro dissolution tests were conducted. The European Pharmacopeia test did not detect any differences between the products. At pH 5, both with and without mechanical stress, only the product with the shortest tlag released diclofenac. The in vivo results were best predicted by the in vitro dissolution tests performed at several fixed pH values with mechanical stress.

Current regulatory (draft) guidance on chiral medicinal products: Canada, EEC, Japan, United States.

The rapid development of stereospecific analytical, synthetic, and preparative methods has profoundly changed the prospects for development and application of chiral medicinal products. This has induced regulatory agencies, e.g., in Canada, the EEC, Japan, and the United States, to prepare guidance on this subject. The present draft documents are discussed, with emphasis on the two most important cases: (1) New racemates: How many extra requirements are justified? (2) Development of a single enantiomer from an approved racemate: how few are acceptable? At the moment the opportunities for early harmonisation are favourable and the formulation of one international guidance document seems feasible.

Bioavailability and bioequivalence requirements in the European community.

An comparative overview is given of the new EC-Note for Guidance on bioavailability and bioequivalence, which now has been sent out for consultation to interested parties. The new version gives more regulatory detail than the version of 1984. It is expected that it will come into force in the course of 1991. Some changes in the final version as compared to the present version, accepted by the CPMP, are possible. The EC-Note for Guidance on modified-release products, which came into force in July 1990, has also been discussed. In comparison with comparable guidance in other areas off the world this guidance gives much thought to the clinical aspects and especially the clinical justification of modified-release products.

Comparative antidotal efficacy of activated charcoal tablets, capsules and suspension in healthy volunteers.

The efficacy of several formulations of activated charcoal (AC) was compared by measuring the intestinal absorption of a solution of 1 g paracetamol administered 2 min before administration of 5 g AC as suspension (200 ml), tablets (40 of 125 mg) or capsules (25 of 200 mg). The suspension medium without AC was used as the control treatment. Based on the results of a pilot experiment, an 8 subject panel was used in a two 4 x 4 Latin square design. All treatments with AC resulted in a statistically significant decrease in paracetamol absorption compared to the control treatment. The suspension was considerably and significantly more effective than the tablets or capsules. Treatment with tablets was slightly but significantly more effective than capsules. The intake of large numbers of tablets and capsules was difficult. In the hospital AC suspensions are available. For first aid elsewhere, at home, at the working place or in the general practitioner's surgery a preservable and easily redispersible AC formulation would be preferable to the present solid forms.

Intestinal first pass metabolism of amygdalin in the rat in vitro.

The intestinal first pass metabolism of amygdalin has been investigated in rat small intestine in vitro. The results show that amygdalin is hydrolyzed to prunasin, essentially in the wall of the proximal jejunum. This specific beta(1-6)hydrolytic cleavage of the terminal glucose residue is pH-dependent and can be inhibited by glucono-delta-lactone, a potent inhibitor of the lysosomal beta-glucosidase of the rat intestine. No substrate competition between phloridzin and lactose vs amygdalin was noted. None of the more common soluble beta- or alpha-enzymatic activities of mammalian intestine (alpha-glucosidase, alpha-amylase) or mammalian liver (beta-galactosidase, beta-glucuronidase) were capable of catalyzing the hydrolysis of the terminal glucose from amygdalin at pH's 5.0, 7.0 or 9.0. Furthermore, no metabolic activity of isolated rat livers toward amygdalin and prunasin was observed within two hours of recirculating perfusion. However, cecal contents of conventional rats, exhibited both amygdalin- and prunasin-hydrolyzing activities. The resulting mandelonitrile dissociates spontaneously into cyanide and benzaldehyde. Therefore, our findings indicate that metabolism of amygdalin to prunasin occurring in the proximal part of jejunum is apparently mediated by enzymatic beta(1-6)glucosidase activity of the gut wall. In contrast, the toxicity of amygdalin due to the release of cyanide obviously requires microbiological activities of the gut flora.

[Pharmacokinetic aspects of residues at the injection site]. / Farmacokinetische aspecten van injectieplaats-residuen.

The disappearance of drug residues from slaughter animals treated by intramuscular route can only be reliably predicted when the dose is rapidly and reproducibly absorbed. In actual practice, this will frequently not be the case. The effects of slow absorption for extinction of residues are illustrated by pharmacokinetic simulation. It is concluded that withdrawal times should not be determined for a drug substance but for any intramuscular formulation of that substance.

[Tranquilizers in the transport of slaughtering pigs: a problem of residues?]. / Tranquillizers bij transport van slachtvarkens: een residuprobleem?

Selection of a meatier type of pig previously gave rise to problems during transport because of susceptibility to stress. A symptomatic approach of the problem resulted in administration of tranquilizers prior to transport. The properties of the tranquillizers azaperone and propiopromazine are discussed, as are the results of studies on residues. It is concluded that the residues detected so far are not detrimental to public health. In view of other possible approaches designed to prevent or reduce injury due to transport, the use of tranquillizers not strictly indicated is undesirable.

Pharmacokinetics of bromide ion--an overview.

The recent role of bromide as a residue in food and water necessitated its toxicological investigation. Although much was known already about the absorption, distribution and elimination of bromide, more data were required, especially for the rat. The pharmacokinetics in the rat were therefore investigated, with emphasis on cumulation and on the role of chloride in bromide elimination. This review recapitulates old and recent findings on the fate of bromide.

The influence of sodium bromide in man: a study in human volunteers with special emphasis on the endocrine and the central nervous system.

Sodium bromide was administered orally in capsules to healthy volunteers in doses of 0, 4 or 9 mg Br-/kg/day using a double-blind design. Each treatment was given to seven males for 12 weeks and to seven non-pregnant females (not using oral contraceptives) over three full cycles. Special attention was paid to possible effects on the endocrine and central nervous systems. At the start and end of the study, a full medical history, the results of a physical examination, haematological studies and standard clinical chemistry and urine analyses were recorded for each subject. These showed no changes for individuals following treatment, except for some incidence of nausea associated with bromide-capsule ingestion. Mean plasma-bromide concentrations at the end of treatment were 0.08, 2.14 and 4.30 mmol/litre for males and 0.07, 3.05 and 4.93 mmol/litre for females of the 0-, 4- and 9-mg Br-/kg/day groups, respectively. Plasma half-life was about 10 days. In the females taking 9 mg Br-/kg/day (but in no other group) there was a significant (P less than 0.01) increase in serum thyroxine and triiodothyronine between the start and end of the study but all concentrations remained within normal limits. No changes were observed in serum concentrations of free thyroxine, thyroxine-binding globulin, cortisol, oestradiol, progesterone or testosterone, or of thyrotropin, prolactin, luteinizing hormone (LH) and follicle-stimulating hormone before or after the administration of thyrotropin-releasing hormone and LH-releasing hormone. Analysis of neurophysiological data (EEG and visual evoked response) showed a decrease in delta 1- and delta 2-activities and increases in beta-activities and in mean frequency (Mobility parameter) in the groups on 9 mg Br-/kg/day, but all the findings were within normal limits.

Etomidate-anaesthesia, with and without fentanyl, compared with urethane-anaesthesia in the rat.

In spontaneously breathing rats, continuous infusion of etomidate with and without fentanyl caused a slight decrease in blood pressure and heart rate. Coadministration of fentanyl and etomidate in order to obtain full anaesthesia and analgesia resulted in respiratory depression. In artificially ventilated rats both etomidate as well as the anaesthetic combination caused a strong reduction in aortic flow and an increase in total peripheral resistance. A single infusion of etomidate did not change blood pressure. Etomidate combined with fentanyl reduced blood pressure. Under adjusted ventilation blood pressure, aortic flow, max(dF/dt) and heart rate were progressively reduced during a 4 h period. In contrast, urethane anaesthesia reduced aortic flow to a minor extent. Total peripheral resistance and max(dF/dt) were hardly affected. The slightly reduced blood pressure and blood gas variables remained stable during the experiment. From pharmacokinetic studies it was established that effective etomidate plasma levels were maintained constant during the experimental period. Pharmacokinetic interaction between etomidate and fentanyl did not occur. It is concluded that for anaesthesia of longer duration during cardiovascular experiments in rats, urethane is preferable to etomidate/fentanyl because it does not cause serious changes in basal haemodynamic variables.

Determination of amygdalin and its major metabolite prunasin in plasma and urine by high pressure liquid chromatography.

A method is described for the determination of amygdalin and prunasin in plasma ultrafiltrate and urine. Both compounds are separated by high pressure liquid chromatography on a reversed phase column and subsequently detected at 215 nm. The identity of an amygdalin metabolite with prunasin was confirmed by mass spectrometry.

The pharmacokinetics of prunasin, a metabolite of amygdalin.

The pharmacokinetics of prunasin have been investigated in the dog. The results are compared with results obtained with amygdalin. The volume of distribution and the clearance of prunasin are larger than those of amygdalin. The oral bioavailability of prunasin is approximately 50%, whereas amygdalin is hardly absorbed unchanged.

Study of sodium bromide in human volunteers, with special emphasis on the endocrine system.

1 Bromide, 1 mg kg-1 daily, was administered to 21 healthy volunteers (11 females not using oral contraceptives and not pregnant and 10 males, during 8 weeks or 2 full cycles to determine whether ingestion of a dose equal to the acceptable daily intake might induce effects. Special attention was paid to the endocrine system because endocrine changes were predominant in rats receiving sodium bromide (NaBr) in their diets. 2 There was no difference between the results of a full medical history and physical examination at the start and at the end of the experiment. 3 The results from the measured haematological, biochemical and urine analyses did not change during the experiment. 4 In females the plasma bromide concentration rose from 0.08 +/- 0.01 mmol 1(-1) to 0.97 +/- 0.18 mmol 1(-1) and in males from 0.08 +/- 0.01 mmol 1(-1) to 0.83 +/- 0.09 mmol 1(-1) (mean +/- s.d.). 5 No changes were observed in the serum concentrations of thyroxine, free thyroxine, thyroxin binding globulin, triiodothyronine, cortisol, testosterone, estradiol and progesterone. Also no changes were observed in the serum concentrations of thyroid stimulating hormone (TSH), prolactin, luteinizing hormone (LH) and follicle stimulating hormone (FSH) before and after the administration of thyroid stimulating hormone releasing hormone (TRH) and luteinizing hormone releasing hormone (LHRH).

The pharmacokinetics of amygdalin.

Amygdalin (D-mandelonitrile-beta-D-gentiobioside) is a cyanogenic glycoside claimed to show anti-cancer activity, sold under the incorrect name "Laetrile". For a sensible discussion of its alleged activity and its established toxicity it is necessary that its fate in the organism is known. The pharmacokinetics of amygdalin have been investigated in the Beagle dog after both intravenous and oral administration. The excretion of amygdalin has also been studied in the rat. Amygdalin concentrations were determined by high performance liquid chromatography in plasma ultrafiltrate and urine. The pharmacokinetics of amygdalin after intravenous administration were compared with those of diatrizoate, a model substance for extracellular volume and glomerular filtration. The amygdalin clearance is significantly larger than that of diatrizoate. The volumes of distribution of both substance are the same. After oral administration only a few percents of the amygdalin dose are systemically available. A part of the oral dose is recovered from the urine as prunasin (D-mandelonitrile-beta-D-glucoside).

The determination of propiopromazine in animal tissue.

A thin-layer chromatographic method for the determination of the veterinary tranquillizer propiopromazine (Combelen) in slaughter pigs is described. Propiopromazine residue depletion from the kidney occurs with different rates in sows and in castrated boars. In the liver residues increase over at least 24 h after intramuscular administration, in accordance with the distribution pattern of phenothiazine tranquilizers.