DT-DS: CAN Intrusion Detection with Decision Tree Ensembles

The controller area network (CAN) protocol, used in many modern vehicles for real-time inter-device communications, is known to have cybersecurity vulnerabilities, putting passengers at risk for data exfiltration and control system sabotage. To address this issue, researchers have proposed to utilize security measures based on cryptography and message authentication; unfortunately, such approaches are often too computationally expensive to be deployed in real-time on CAN devices. Additionally, they have developed machine learning (ML) techniques to detect anomalies in CAN traffic, and thereby prevent attacks. The main disadvantage of existing ML-based techniques is that they either depend on additional computational hardware, or they heuristically assume that all communication anomalies are malicious.

In this paper, we show that tree-based learning ensembles outperform anomaly-based techniques like ARIMA and Z-Score when used to detect attacks that result in increased bus utilization. We evaluated the detection capacity of three tree-based ensembles, Adaboost, gradient boosting, and random forests, and collectively refer to these as DT-DS. We conclude that the decision tree ensemble with Adaboost performs best with an area under curve (AUC) score of 0.999, closely followed by gradient boosting and random forests with 0.997 and 0.991 AUC scores, respectively, when trained using message profiles. We observe that with an increase in the observation window, the DT-DS models present an average AUC score of 0.999, and offer a nearly perfect detection of attacks, at the cost of increased latency in detection of attacked messages. We evaluate the performance of the IDS for ARINC-encoded CAN communication traffic in avionic systems, generated using an aerospace testbench, ARINC-825TBv2. The IDS has been evaluated against the active attacks of a state-of-the-art predictive attacker model. Additionally, we observed that the performance of IDS approaches such as ARIMA and Z-Score degrade considerably with a decrease in the size of the observation time window. In contrast, the performance of DT-DS models is consistent, with only an average drop of 0.005 in the AUC score.

Multiple doses of trandolapril do not affect warfarin pharmacodynamics

OBJECTIVE

The effects of multiple doses of trandolapril (a new angiotensin-converting enzyme inhibitor) on the pharmacodynamics of a single 25 mg dose of warfarin were investigated in 19 men.

DESIGN

A double-blind, placebo-controlled cross-over design was used. The study consisted of two periods of 13 days each, during which subjects received either trandolapril 2 mg or placebo once daily according to a randomisation plan. Warfarin was given on day 8 of each of these periods.

SETTING

The study was carried out at the Hoechst Research Centre for Clinical Pharmacology, Department of Pharmacology, University of the Orange Free State, Bloemfontein.

PATIENTS

Nineteen healthy white men aged between 18 and 28 years and weighing between 65 and 98 kg volunteered for the study.

OUTCOME MEASURES

Prothrombin time (PT) and coagulation factors II, VII, IX and X were measured before and sequentially up to 6 days after warfarin administration. Areas under the PT and coagulation factor time curves for warfarin + trandolapril were compared with the corresponding areas for warfarin + placebo. The two treatment combinations were also compared at each measuring time.

RESULTS

The point estimate for the ratio of the treatment means of warfarin + trandolapril relative to warfarin + placebo for PT was 97% (90% confidence interval: 90%-103%). The corresponding value for factor VII was 97% (90% confidence interval: 91%-102%).

CONCLUSION

The concomitant administration of trandolapril did not affect the pharmacodynamic effects of warfarin.

The effects of buserelin microparticles on ovarian function in healthy women

OBJECTIVE

To investigate the tolerance, pharmacokinetics and pharmacodynamics of the microparticle formulation of buserelin, when it was administered subcutaneously.

DESIGN

A single-blind, randomised, parallel-group design was used to investigate the duration of suppression of ovarian function associated with doses of 1.8 3.6 and 7.2 mg buserelin administered subcutaneously as microparticles.

SETTING

The study was carried out at the Hoechst Research Centre for Clinical Pharmacology, Department of Pharmacology, University of the Orange Free State, Bloemfontein.

PATIENTS

Thirty-two health premenopausal female volunteers aged between 19 and 39 years and weighing between 52 and 85 kg completed the study.

OUTCOME MEASURES

Serum progesterone and oestradiol concentrations were measured twice weekly until normal ovarian function resumed, i.e. when serum progesterone concentrations increased to at least 8 nmol/l (a sign of ovulation) and oestradiol concentrations increased to values above 300 pmol/l. Serum and urinary concentrations of buserelin were measured at the same times as those of progesterone and oestradiol.

RESULTS

Doses of 1.8 3.6 and 7.2 mg elicited anovulation for mean periods of 52, 77 and 113 days and suppressed ovarian production of oestrogen for 19, 38 and 69 days. Resumption of normal ovarian function occurred when serum buserelin concentrations decreased to between 0.03 and 0.05 microgram/ml. The correlation coefficient between dose and duration of anovulation was 0.75; the correlation coefficient between dose and duration of suppression of oestrogen production was 0.76.

CONCLUSION

Apart from minor side-effects such as hot flushes, vaginal spotting and acne, the compound was tolerated well. We conclude that a good relationship exists between dose and duration of suppression of ovarian function. Doses of 3.6 - 7.2 mg buserelin should suppress oestrogen production for approximately 6 - 9 weeks and ovulation for 11 - 16 weeks.

The effect of fasting on total serum bilirubin concentrations

Thirty-seven healthy volunteers, 19 of whom had consistently elevated total serum bilirubin (TSB) concentrations, took part in an open, randomised cross-over study to determine the effect of fasting on TSB concentrations. The study comprised of two treatments. During one treatment period volunteers ate a standard supper but fasted for 24 h thereafter. During the other treatment period volunteers ate a standard supper, snacks, breakfast and lunch. TSB concentrations were measured at regular intervals. In both the normal and high bilirubin groups, minimum TSB values were recorded 4 h after the supper. A 24 h fast more than doubled TSB concentration from baseline values in both the normal and high bilirubin groups. A clinically relevant rise in TSB took place after 12 h into the fasting period (TSB of 17.3 mumol l-1 in the fasted group vs 14.0 mumol l-1 in the non-fasted group). When designing a clinical trial, selecting volunteers, or judging the tolerance of a new drug, the rise in TSB caused by fasting must therefore be taken into account, particularly in trials where volunteers or patients fast before entering the study.

Lack of interaction between ramipril and simvastatin

Twenty two healthy males participated in a randomised, placebo-controlled, double blind, cross-over study to investigate the influence of simvastatin on the pharmacokinetics of ramipril and its active metabolite (ramiprilat), and on the ACE-inhibiting effect of ramiprilat. During two study periods, each of 7 days, subjects received daily either simvastatin 20 mg at 19.00 h or placebo; ramipril (5 mg) was given on Day 5 of each of the periods. Plasma concentrations of ramipril and ramiprilat and ACE-activity were measured in sequential blood specimens, and ramipril and ramiprilat concentrations were measured in urine. Blood and urine collections for pharmacokinetic and pharmacodynamic assessment were made up to 72 h after the dose of ramipril. The mean AUC of ramipril for ramipril+placebo (R+P) and ramipril+simvastatin (R+S) was 22.2 and 21.3 ng.h.ml-1, respectively; for ramiprilat the corresponding figures were 61.3 and 57.6 ng.h.ml-1. The urinary excretion of ramipril+metabolites for (R+P) and (R+S) was 25.2 and 24.1% of dose. The maximum percentage inhibition of ACE-activity for (R+P) was 94.6%, and for (R+S) it was 94.1%. It is concluded that concomitant administration of simvastatin and ramipril has no clinically relevant effect on the pharmacokinetics or ACE-inhibition of the latter drug and its metabolites.

Assessing the risk of ovulation in interaction studies of drugs and oral contraceptives

When certain drugs are taken concomitantly with an oral contraceptive, the efficacy of the contraceptive may be obtunded, and pregnancy may ensue. Since the function of oral contraceptives is to suppress ovulation, the risk of ovulation is an important parameter in clinical studies investigating interactions between drugs and oral contraceptives. The purpose of this paper is to compare a crossover design, and a new study design used for assessing a possible interaction between a drug and an oral contraceptive, and to discuss the statistical issues involved in the planning and evaluation of the results of such studies.

Effect of renal function on the pharmacokinetics and pharmacodynamics of trandolapril

1. The pharmacokinetics and pharmacodynamics of a single dose of trandolapril, an angiotensin converting enzyme (ACE) inhibitor with an active metabolite, trandolaprilat, which is in part further metabolised prior to renal elimination, were evaluated in 31 subjects with a wide range of renal function (creatinine clearance 4-112 ml min-1 1.73 m-2). 2. The pharmacokinetics of trandolapril were unaffected by differences in renal function. 3. In contrast, there was a close correlation between the renal clearance (0-96 h) of trandolaprilat and creatinine clearance (r = 0.95, P = 0.0001). The maximum plasma concentration of trandolaprilat, and the area under the concentration curve (0-96 h) correlated inversely with creatinine clearance (r = -0.59, P < 0.001; and r = -0.61, P < 0.001 respectively). 4. Significant changes in plasma trandolaprilat concentrations were seen only in patients with creatinine clearances of 30 ml min-1 1.73 m-2 or less, suggesting that a dose reduction in trandolapril might be advisable in severe renal impairment. 5. However, the majority of parameters of ACE inhibition were unrelated to creatinine clearance, although area under the curve for ACE inhibition (0-336 h) showed a weak negative correlation (r = -0.49, P < 0.01). Similarly, weighted mean changes in blood pressure were not influenced by renal function. 6. Therefore, while the pharmacokinetic parameters of trandolaprilat correlated with creatinine clearance, pharmacodynamic measurements (ACE inhibition and blood pressure changes) in general showed no such relationship, indicating that dose adjustment of ACE inhibitors in renal impairment should be based on pharmacokinetic results only in conjunction with pharmacodynamic data.

Recombinant hirudin, a new anticoagulant, has no effect on faecal blood loss

Hirudin is a selective thrombin inhibitor with strong anticoagulant properties which could elicit gastro-intestinal bleeding. A double-blind cross-over study of the effects of hirudin on gastro-intestinal bleeding was therefore conducted on 12 healthy, consenting males. After labelling erythrocytes with 51Cr and returning them intravenously, stools were collected for 2 days to measure radioactivity and hence baseline faecal blood loss. After injection of hirudin or placebo stools were collected for 3 days. Partial thromboplastin time was measured sequentially after medication with hirudin or placebo. This procedure was repeated after injection of the alternate medication 1 week later. Hirudin was tolerated well. Mean faecal blood loss associated with hirudin was slightly higher than with placebo (1.63 ml vs 1.15 ml over 3 days; 95% confidence interval for the difference between hirudin and placebo was -0.68 to 1.63) but these differences are clinically irrelevant. After hirudin injection PTT was elevated to about twice the baseline values but returned to baseline within 12 h after the last hirudin injection.

Safety, tolerance and pharmacokinetics of cefpirome administered intramuscularly to healthy subjects

The pharmacokinetics of cefpirome were studied in healthy male subjects following single (0.5, 1.0 and 2.0 g) and multiple (1.0 g every 12 h for 3.5 days) intramuscular injections. High pressure liquid chromatography was used to determine cefpirome concentrations in plasma and urine. Cefpirome was absorbed rapidly, mean peak times were 1.6-2.3 h. Pharmacokinetics were linear over the 0.5 to 2.0 g range with mean total body clearance ranging from 148 to 154 mL/min. The peak plasma concentration and area under the curve increased in a dose proportional manner. The terminal half-life (2 h) was not influenced by dose or duration of dosing. There was no drug accumulation after multiple in administrations. About 70-80% of an administered dose was excreted in the urine as unchanged cefpirome. Cefpirome was well tolerated, slight to moderate pain being reported in less than 30% of the injections.

The effects of felodipine on the pharmacokinetics of diazepam

Twelve consenting, caucasian male volunteers participated in a double-blind, randomized, crossover study of the effects of felodipine, a calcium antagonist, on the pharmacokinetics of diazepam. There were two trial periods of 12 days each with a wash-out period of 9 days between them (total duration: 12 + 12 + 9 = 33 days). During the 12-day periods they received either felodipine or placebo each morning under fasting conditions. On day 6 of each of the two 12-day periods, diazepam, 10 mg was injected i.v. 30 minutes after the felodipine/placebo. Diazepam and desmethyldiazepam concentrations were measured in plasma up to 168 hours after the injection. Diazepam plasma concentrations and pharmacokinetic parameters were not affected by the concomitant medication with felodipine. However, the co-administration of felodipine increased desmethyldiazepam plasma concentrations relative to placebo: mean area under the plasma concentration-time curve of 4,910 vs 5,581 ng.h/ml and mean peak concentrations of 40 vs 47 ng/ml. Felodipine might cause a retarded elimination of desmethyldiazepam, possibly by obtruding the formation of oxazepam. The clinical relevance of these findings remains to be elucidated.

The pharmacology of recombinant hirudin, a new anticoagulant

A new anticoagulant, recombinant hirudin, was given to healthy volunteers (5 per test dose) in single intravenous doses of 0.01, 0.02, 0.04, 0.07 and 0.1 mg/kg to study its anticoagulant effects, how it was tolerated and its pharmacokinetics. Hirudin proved to be a potent anticoagulant with important effects on thrombin (increase in thrombin time and partial thromboplastin time). The maximum pharmacodynamic effect was achieved with the 0.07 mg/kg dose, and upwards. All doses of the compound were tolerated without side-effects. The mean elimination half-life is about 1 hour. Mean total clearance and volume of distribution are approximately 190 ml/min and 14 l, respectively. Hirudin obeys first-order pharmacokinetics.

Statistical significance versus clinical relevance. Part III. Methods for calculating confidence intervals

Formulae for calculating confidence intervals for different types of studies and conditions are presented. These include means, proportions, difference in means and proportions for paired and unpaired data, more complicated analyses of variance, medians, quantiles, relative risks (odd ratios), standardised ratios and rates, intercepts, slopes and correlation coefficients in regression and correlation analyses, as well as survival proportions calculated in survival analysis. For less frequently used formulae, examples are included.

Statistical significance versus clinical relevance. Part II. The use and interpretation of confidence intervals

Most clinical studies are carried out to estimate some quantity, such as a difference in means or proportions. However, significance testing without controlling the power of the test is not an appropriate tool for this purpose, since practical conclusions are difficult (or even impossible) to formulate. The use of confidence intervals, which provide effective information in this regard, is recommended and illustrated by means of an example. With confidence intervals, it can clearly be stated in what range the population value (difference, proportion, or any other point estimate) is likely to lie. A clinically relevant interpretation can then be made without difficulty.

Statistical significance versus clinical relevance. Part I. The essential role of the power of a statistical test

When comparing two treatment groups, hypothesis testing is widely used. However, clinical trialists should be more interested in statistical methods which elicit the magnitude of the differences between treatment groups, rather than a simple indication of whether or not the differences are statistically significant. Statistical significance does not necessarily imply clinical relevance. If the true difference between two treatment groups is so small that it is clinically irrelevant, a sample size can be found for which this difference is statistically significant. On the other hand, if the difference between treatment groups is statistically non-significant, it may still be clinically important. The limitations of conventional hypothesis testing of equal true means as such are highlighted. The need to control the power of the test--which takes into account the difference in treatment means which is considered important (clinically relevant) by the researcher--is discussed.

Bio-availability of three formulations of glibenclamide

Eighteen healthy men participated in a double-blind, randomised, crossover study to compare the bio-availability of three 5 mg formulations of glibenclamide. The products compared were Daonil (Hoechst), Glycomin (Lennon) and Melix (Lagamed). Volunteers received a continuous intravenous infusion of glucose at a rate of 0.25 g/kg/h for 10 hours. Two hours after commencement of this infusion medication was given orally with 200 ml of a 10% (m/v) glucose solution. The subjects also drank 200 ml of the glucose solution hourly for 5 hours after medication. Blood samples were taken up to 22 hours after medication for radio-immunoassay of glibenclamide as well as for measurement of glucose concentrations. The following kinetic variables were calculated; maximum concentration, time to maximum concentration, terminal half-life, areas under the serum concentration-time curves, relative total clearance, total mean time and relative volume of distribution. Daonil and Glycomin were bio-equivalent, but important differences were demonstrated between these two formulations and Melix. This study method necessitates close surveillance of volunteers in order to detect and treat hypoglycaemia.

Effects of HOE 760 (histamine H2-receptor antagonist) on diazepam pharmacokinetics

A double-blind cross-over study of the effects of HOE 760 (histamine H2-receptor blocker) on diazepam pharmacokinetics was conducted in 12 healthy men. HOE 760 or placebo was given daily for 12 days and, after a wash-out period of 9 days, the alternate medication was given for 12 days. Diazepam 10 mg was given intravenously on day 6 of each of the 12-day periods. Blood was taken up to 1 week after the diazepam injections for assay of diazepam and desmethyldiazepam. The co-administration of HOE 760 did not affect the pharmacokinetics of diazepam and desmethyldiazepam.

The effects of forskolin eye drops on intra-ocular pressure

Two studies were performed to investigate the effects of forskolin (Hoechst Research) on intra-ocular pressure (IOP). In the first study two 1.0% formulations of forskolin eye drops were compared with placebo in 10 healthy volunteers. Oxybuprocaine eye drops were used for local anaesthesia before measurement of IOP by applanation tonometry. This was followed by instillation of either medication or placebo on a randomised cross-over basis and hourly measurement of IOP. No significant differences were present between the forskolin treatments and placebo. For 6 hours after drug application a definite decrease in IOP relative to base-line values was observed after each of the forskolin treatments as well as after placebo. In a subsequent study only one formulation of 1% forskolin was compared with placebo. Proxymetacaine eye drops were used for local anaesthesia. Forskolin resulted in a significant reduction in IOP relative to placebo. It is concluded that forskolin reduces IOP in healthy volunteers, and that oxybuprocaine reduces IOP in its own right.

Pharmacokinetics of ramipril in the elderly

Ramipril (HOE 498) is a pro-drug of which the main metabolite (HOE 498 diacid or ramiprilat) is a potent angiotensin converting enzyme inhibitor. Thirteen healthy white volunteers (5 females and 8 males, ages 65 to 76 years) participated in a study to investigate the pharmacokinetics of HOE 498 in the elderly. After administration of 10 mg of HOE 498, sequential urine and serum specimens were obtained for assay of HOE 498 and metabolites (HOE 498-glucuronide, diacid, diacid-glucuronide, diketopiperazine and diketopiperazine acid). Side effects, clinical chemistry and hematology were monitored. HOE 498 reached peak concentrations of 62.4 +/- 23.3 ng/ml in serum after 0.7 +/- 0.3 hours. Serum levels decreased with an apparent half-life of 0.9 +/- 0.4 hours. The diacid was rapidly formed in serum, reaching peak concentrations of 40.6 +/- 14.0 ng/ml after 2.0 +/- 0.6 hours and declining with a half-life of 2.2 +/- 0.5 hours. A prolonged terminal phase of serum concentration versus time curve was observed at concentrations less than 1 ng/ml. The mean recovery of HOE 498 and metabolites in urine, up to 26 hours after administration, was 35 +/- 14% of the dose. The apparent half-lives, calculated from urine parameters, for HOE 498 and the diacid were 2.6 +/- 0.9 and 4.0 +/- 1.1 hours, respectively. The mean peak concentration and half-life of HOE 498 in serum are slightly higher in the elderly than in younger volunteers. Complete urinary collection was not possible, but urinary recovery did not seem different from younger volunteers.

Kinetics of piretanide absorption from the gastrointestinal tract

In a recent report, it was shown that the loop diuretic piretanide is rapidly absorbed after placement of a piretanide solution in the duodenum, while the rate of absorption is definitely slower when the drug is instilled into the ascending colon (5). When piretanide is instilled into the stomach, the absorption process does not differ significantly from that after placement in the duodenum, neither with respect to amount nor rate (5). However, it was not clear from this study whether piretanide is directly absorbed from the stomach or rapidly released into the duodenum. In a study with five volunteers piretanide was instilled into the stomach via a gastroscope. The volunteers took part in two trial phases in a randomized cross-over design: in one phase the administration of 6 mg piretanide was preceded by intravenous administration of 40 mg hyoscine-N-butylbromide (HNB) to immobilize the stomach while in the alternative phase this coadministration of HNB was omitted. Furthermore, the volunteers were lying on their left side to avoid the gastric fluid leaking out into the intestine by gravity. From the concentration-time-curves monitored it can be concluded that piretanide is absorbed directly from the stomach for almost all subjects but with different rates. The rate of absorption increases clearly when the immobilizing effect of HNB disappears. It is most probable that returning peristaltic waves and succeeding gastric emptying results in enhanced absorption from the upper intestinal tract. Furthermore, a pharmacokinetic model which takes into account the differences in the rate of absorption along the gastrointestinal tract was adjusted to the data.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparative bio-availability of four formulations of furosemide

Twelve healthy white male volunteers participated in a randomized double-blind cross-over study to compare the bio-availability of four brands of furosemide marketed in the RSA. A 40 mg tablet of each of the following formulations, purchased at random, was administered: Aquasin; Furetic; Lasix; and Puresis. Blood specimens were taken up to 5 hours and urine specimens collected up to 6 hours after medication. The following parameters were used to compare the formulations: (i) area under the plasma concentration time curve (AUC); (ii) maximal plasma concentration of furosemide (Cmax); (iii) time to maximal furosemide plasma concentration; (iv) cumulative urine volumes; and (v) cumulative excretion of furosemide in urine. Lasix was significantly superior to the other three products in respect of AUC and Cmax. With regard to cumulative urine volumes Lasix was significantly (P less than 0,05) superior to Aquasin in the first 3 hours after medication, significantly superior (P less than 0,05) to Puresis and comparable to Furetic over the entire 6-hour collection period. Lasix resulted in a significantly greater cumulative urinary excretion of furosemide than Puresis and Aquasin over the entire collection period. Lasix was superior to Furetic at 6 hours after medication. It is concluded that the bio-availability of Lasix is superior to that of the other products tested.

Effects of piretanide on potassium balance in hypertension

Ten hypertensive patients completed a trial lasting 12 weeks to measure the effect of long-term treatment with piretanide, a new, powerful 'loop' diuretic, on total body potassium (TBK). After 2 weeks of placebo treatment, they received 6 mg piretanide twice daily. This dose was increased to 6 mg 3 times a day if blood pressure was not satisfactorily lowered after 4 weeks. Blood pressure and plasma potassium levels were measured weekly. The TBK was measured fortnightly. In this study potassium balance was not significantly affected by the administration of piretanide.

Cardiovascular effects of etilefrine hydrochloride during abdominal aortic surgery

To counteract the decrease in blood pressure after release of the aortic cross-clamp, 2 mg etilefrine hydrochloride (Effortil; Boehringer Ingelheim) was administered intravenously to 13 patients undergoing aortofemoral bypass operations. It caused a statistically significant increase in mean arterial pressure, cardiac index, pulmonary capillary wedge pressure and left and right ventricular stroke work index. No significant changes were found in total peripheral resistance.

Antagonism of diazepam by aminophylline in healthy volunteers

Six healthy volunteers participated in a randomized, double-blind cross-over study of the effects of intravenous aminophylline on diazepam-induced sedation. Each subject participated in two phases and in each phase received either diazepam (15 mg intravenously) followed by placebo or diazepam followed by aminophylline (2 mg/kg intravenously). Critical flicker fusion times and reaction times were measured sequentially as indices of vigilance. Subjects also assessed their own vigilance on a visual analogue scale. Aminophylline given after diazepam significantly improved vigilance as measured by the visual analogue scale from 60 to 150 min after administration of diazepam, while total reaction time was significantly improved at 90, 210, and 270 min. There was no significant correlation between theophylline plasma levels and its effects on vigilance.

Effects of tendamistate (an alpha-amylase inactivator), guar and placebo on starch metabolism

Nine volunteers participated in a double-blind, cross-over study to compare the effects of tendamistate (HOE 467), guar and placebo on starch metabolism. In each phase of the trial they received a maize-meal porridge breakfast. They either received 5 g guar granules before the porridge or 100 mg tendamistate mixed with the porridge, or porridge alone. Sequential plasma glucose concentrations served as a criterion of starch digestion. The area under the plasma glucose curve and maximal glucose concentrations after administration of tendamistate with the starch were significantly lower (P less than 0,05) than after guar and placebo. No significant differences were found between placebo and guar. We concluded that tendamistate effectively attenuates starch digestion and is superior to guar in reducing postprandial glycaemia.

Effects of tendamistate on postprandial plasma glucose, free fatty acid and triglyceride levels

A dose of 400 mg tendamistate or a placebo was given to 10 volunteers in order to investigate its effects on plasma glucose, free fatty acid and triglyceride levels after a porridge meal. Each subject participated in two phases, in each of which they ate porridge prepared from 100 g maize meal together with either placebo or tendamistate 400 mg. Serial blood specimens for plasma glucose determinations were taken up to 3 hours after the meal, and those for free fatty acid and triglyceride determinations up to 14 hours after the meal. Side-effects (flatulence and bulky stools) were not severe and were reported after both treatments. Tendamistate administration significantly attenuated postprandial glycaemia; it had no effect on postprandial triglyceride levels and was associated with a reduction in free fatty acid levels.

Pharmacodynamics and tolerability of low doses of tendamistate given with starch

Six healthy male volunteers participated in a double-blind cross-over study in which 12,5 mg, 25 mg, or 50 mg tendamistate (HOE 467), an alpha-amylase inactivator, or placebo were administered with 100 g maize meal, which contains 85,5 g pure starch. Serial blood specimens for measurement of plasma glucose concentrations, which served as a criterion of starch absorption, were taken up to 3 hours after each starch meal, and side-effects were recorded. The administration of HOE 467 with a starch meal resulted in a significant inhibition of starch absorption. Side-effects were not severe. Flatulence occurred in the placebo phase as well as after administration of the active drug. Loose stools were reported by 1 subject after 25 mg tendamistate.

Inhibition of starch absorption by tendamistate (an alpha-amylase inactivator)

Tendamistate (HOE 467) is an alpha-amylase inactivator. Doses of 100 and 200 mg and a placebo were administered to 6 volunteers in order to investigate the effect of the drug on plasma glucose levels after a bread meal. Each subject participated in three phases, in each of which they received a meal consisting of 200 g white bread together with either placebo or tendamistate 100 or 200 mg. Serial blood specimens for plasma glucose determinations were taken up to 3 hours after the meal. Plasma glucose concentrations served as a criterion of starch absorption. Side-effects (flatulence and/or diarrhoea) were reported after each of the three treatments. The administration of tendamistate together with the bread meal resulted in significant inhibition of starch absorption.

Effects of tendamistate (alpha-amylase inactivator) on starch metabolism

1 Tendamistate (Hoe 467) reduces gastrointestinal absorption of starch by inactivating α-amylase.

2 Two trials were performed to investigate the influence of timing and mode of administration of tendamistate, relative to starch intake, on the pharmacodynamics of the drug.

(i) In the first trial 400 mg enteric coated capsules, 400 mg non-enteric coated capsules and placebo were compared in 12 volunteers.

Medication (400 mg tendamistate capsules or placebo) was administered after 10 h fasting, 15 min before a starch meal. Post-prandial plasma glucose concentration-time curves were plotted. No significant differences could be shown between tendamistate capsules and placebo in respect of areas under the curve (AUC), maximal concentration (C_max) and time to maximal concentration (t_max). No side effects were reported.

(ii) In a second trial tendamistate powder, mixed with a starch meal, was compared with placebo in eight volunteers. Blood specimens for measurement of glucose, insulin and C-peptide were taken up to 8 h after this starch meal. AUC as well as C_max in respect of glucose values were significantly lower after Hoe 467 plus starch than after placebo plus starch. Insulin and C-peptide values were closely correlated with glucose. Flatulence and diarrhoea were reported by two subjects.

3 It is concluded that the administration of tendamistate with, but not prior to, starch ingestion is effective in reducing post-prandial glucose levels.

The use of renal enzymes as early indication of renal toxicity after multiple-dose administration of aspirin

Ten volunteers participated in a study comparing the effects on renal enzymes of multiple oral doses of aspirin relative to no treatment. The total urinary output was collected daily for 21 days from all subjects. The first 7 days were treatment-free. During the second 7-day period the subjects received aspirin 1500 mg 3 times daily. This was followed by another treatment-free period of 7 days. The activity of the enzymes alanine aminopeptidase and N-acetyl-beta-glucosaminidase were determined in each daily urine specimen. Statistical analysis revealed that aspirin significantly increased the output of both enzymes.

Pharmacokinetic aspects of the interaction between clobazam and cimetidine

The pharmacokinetic interaction between clobazam and cimetidine was studied in 9 healthy male volunteers in an open-labelled study. After a single oral dose of clobazam 30 mg, a wash-out period of 14 days was followed by daily doses of cimetidine 1 g for one week. Thereafter a single oral dose of clobazam 30 mg was again given. The plasma concentrations of clobazam and its main metabolite N-desmethyl-clobazam were measured by gas-chromatography. The area under the curve (AUC0-infinity) of plasma clobazam level was significantly larger after pretreatment with cimetidine and the elimination half life of clobazam was significantly longer. There were no statistically significant differences in Cmax and tmax for plasma clobazam. The plasma levels of N-desmethyl-clobazam did not show any significant change after the intake of cimetidine.

Pharmacodynamics and urine pharmacokinetics of three doses of piretanide

Three doses (3 mg, 6 mg and 12 mg) of piretanide, a new high ceiling diuretic, and placebo were given to 8 volunteers to investigate the relationship between the pharmacodynamic parameters, the dose and its urinary excretion. Intake of food and fluid were standardized from 48 h before until 24 h after drug administration. Urinary output, excretion of unchanged drug, and the excretion and clearance of Na+ and K+ were measured hourly for 7 h after treatment. A clear dose-response relationship was found for cumulative urinary output, cumulative excretion of Na+ and K+, clearance of Na+ and K+ and the urinary sodium/potassium ratio. A significant correlation was found between the net urine volume and the excretion of piretanide per time interval. The clearances of Na+ and K+ were significantly correlated with the excretion of piretanide. Clearance values correlated well with corresponding urine volumes.

Furosemide chronopharmacology

Twelve healthy males participated in a trial to determine whether furosemide diuresis and its effects on electrolyte excretion patterns, aldosterone concentrations and renin activity are subject to diurnal variations. Six treatments were give: placebo at 07h00, 13h00 and 19h00 and furosemide 40 mg at 07h00, 13h00 and 19h00. Each subject participated in six phases. It was found that the time of administration of furosemide does not affect the effect of the drug on sodium and potassium excretion and diuresis. There is a tendency for furosemide to elevate serum aldosterone levels and renin activity regardless of the time of administration.

The effect of fructose on blood alcohol levels in man

Ten volunteers participated in a trial to determine the effect of fructose on blood alcohol levels when given immediately after the administration of ethyl alcohol. The subjects were randomly assigned to receive two 'treatments', viz.: (i) alcohol followed by placebo; and (ii) alcohol followed by fructose. Each volunteer participated in both phases of the study, receiving both forms of treatment with a 7-day 'wash-out' period between the two. The maximal alcohol concentration attained was significantly lower in subjects who had taken fructose immediately after the alcohol. The area under the alcohol concentration time-curve seen after the subjects had taken alcohol plus placebo was significantly greater than that seen after they had taken alcohol plus fructose. A comparison of the blood alcohol levels attained with the two treatments at each sampling time revealed significantly higher concentrations from 45 minutes onwards when alcohol plus placebo was taken. The time taken for the attainment of maximal blood alcohol concentrations was not affected by the addition of fructose.

Potassium balance in piretanide and digoxin treatment

Piretanide, a new potent diuretic, was given to 18 healthy male subjects to determine its effect on serum, total body (TBK), and red cell potassium (RCP). TBK and RCP were measured before treatment to establish baseline values, after which all subjects received 6 mg piretanide a day for 14 days. After this period subjects were divided into two groups; group 1 received 6 mg/day piretanide for 14 more days and group 2 received the same dose of piretanide with 0.5 mg digoxin daily during the remaining 14 days. All treatments were terminated after 28 days, but subjects remained under observation for another 14 days. Serum potassium, TBK, and RCP were measured weekly during the 42-day period. Piretanide in a dose of 6 mg daily for a period of 6 wk did not induce a fall in serum potassium, TBK, or RCP. The addition of digoxin for 2 wk after piretanide alone for 2 wk did not decrease serum potassium and TBK, but RCP fell under the influence of piretanide with digoxin.

The effect of penbutolol on glomerular filtration

Penbutolol, a new beta-adrenoceptor blocker, was found to increase the glomerular filtration rate (GFR) significantly (16%) relative to placebo when administered orally in a dose of 40 mg daily for 7 consecutive days to healthy males. Measurements were performed after the seventh dose. In contrast, a single acute intravenous dose of penbutolol 4 mg did not influence the GFR, which was determined by means of a gamma counter after intravenous injection of technetium-99m diethylenetriaminepenta-acetic acid. Since penbutolol possesses moderate beta-adrenomimetic activity, it is postulated that the observed increase in the GFR after oral penbutolol could be due to increased cardiac output at rest.

Penbutolol and furosemide in a fixed-dose combination-bio-equivalence of two formulations

Twelve healthy male volunteers participated in an open cross-over study designed to test whether two fixed-dose combination formulations of penbutolol (40 mg) and furosemide (20 mg), an ordinary and a film-coated tablet, are bio-equivalent. Penbutolol capsules (40 mg) and 20 mg furosemide tablets (Lasix; Hoechst) served as reference formulations. The maximum concentration of furosemide was significantly depressed in the case of fixed-dose combinations, reflecting a possible pharmacokinetic interaction between penbutolol and furosemide. However, the area under the concentration versus time curve for furosemide and its cumulative urinary excretion and diuretic effect were not influenced by penbutolol. On the basis of plasma concentration versus time data and urinary parameters, the two fixed-dose formulations are bio-equivalent.

Etomidate as anaesthetic induction agent in open-heart surgery

Etomidate (Hypnomidate; Ethnor (Janssen)) in propylene glycol was used for induction of anaesthesia in 25 patients requiring cardiac surgery, and the effects on pulse and blood pressure were measured. It is concluded that etomidate is a suitable induction agent for open-heart surgery.

[Trancutaneous measurement of arterial oxygen tension during anesthesia]

The transcutaneous oxygen tension was measured in 29 anaesthetized patients by means of a TCM1 TC Oxygen Monitor (radiometer). The correlation coefficient between these transcutaneously determined values and the true PaO2 values was 0,81 as compared with 0,93 in a previous trial in which a Servomed Oxymonitor (Hellige) was used. The effect of diathermy on the TCM1 TC Oxygen Monitor was much less than that on the Hellige apparatus.

[Perforation of the heart during implantation of a transvenous pacemaker. A report on two cases]

Perforation of the right ventricular wall occurred in 2 patients during implantation of a transvenous temporary pacemaker. Although neither of the patients showed any signs of symptoms of pericardial tamponade, blood was found in the pericardial sac at thoracotomy, by means of which epicardial pacemakers were inserted. The possibility of tamponade should therefore be kept in mind when anaesthetizing patients who received a temporary transvenous pacemaker.

[Free-flow electrophoresis. I. Theoretical and experimental investigations of the influence of mechanical and electrokinetic variables on the efficiency of the method]

In the present paper, various types of band-broadening effects in free-flow electrophoresis were investigated. They resulted from the velocity profiles of the liquid curtain and electroosmosis, temperature gradient, thermal diffusion and sample inlet geometry. An analytical free-flow electrophoresis apparatus permitted easy observation of these parameters. The experiments showed that the influence of the temperature gradient was negligible, whereas the effect of the velocity profiles on band broadening was higher than theoretically expected. In preparative work this is of utmost importance, since overlap of bands is not desirable. In this case, the zeta potential of the walls can be adjusted to that of the material to be separated, resulting in a considerable reduction of band broadening. Various approaches are indicated. Further attention was given to the influence of the relaxation effect on the separation. Conditions are shown where particles are separated either according to their surface charge density or to their size. The practical relevance of the results is discussed.