Patients' rights in New Zealand: complaints resolution and quality improvement

"Patients' rights" has become a familiar catchword in western countries in recent years. In New Zealand the Office of the Health and Disability Commissioner was established in 1994 to promote and protect patients' rights. The Commissioner also facilitates the resolution of complaints relating to the infringement of patients' rights as set out in the Code of Health and Disability Services Consumers' Rights. Victims of medical misadventure in New Zealand are compensated through a no-fault, state-funded rehabilitation and compensation scheme. The regulatory environment is rehabilitative rather than punitive. This framework is consistent with a systems approach to reducing errors and improving patient safety, and the Commissioner seeks to use the resolution of individual complaints as a tool for improving the quality of care throughout the health care system.

Lack of bioavailability of mebeverine even after pretreatment with pyridostigmine

OBJECTIVE

After the oral administration of mebeverine to animal or human, measurable concentrations of the drug have never been found in the plasma. The ex vivo hydrolysis of mebeverine can be blocked by esterase inhibitors. In the present study, human volunteers were pretreated with pyridostigmine to attempt to improve the bioavailability of the parent drug.

METHODS

Following a single-blind, random design, 12 normal human volunteers received orally either placebo or 60 mg pyridostigmine, followed 2 h later by 405 mg mebeverine. Blood samples were drawn intermittently for 4 h and were spiked immediately with neostigmine in order to block ex vivo hydrolysis.

RESULTS

Even after pretreatment with pyridostigmine, the plasma samples failed to reveal detectable concentrations of mebeverine. Pyridostigmine pretreatment mediated a significantly higher peak concentration of veratric acid, the acid moiety resulting from hydrolysis of mebeverine.

CONCLUSION

As mebeverine seemingly undergoes complete presystemic hydrolysis, it seems unlikely that the effects of the drug could be mediated centrally. Furthermore, as it is unlikely that sufficient mebeverine traverses the intestine to exert a local effect on the colon (i.e., the time-course of veratric acid plasma levels does not support such a conclusion), the therapeutic effect of the drug, if any, has to be ascribed to an active metabolite. However, the hydrolysis products of mebeverine are not known to be pharmacologically active.

Lack of effect of amitriptyline on risperidone pharmacokinetics in schizophrenic patients

The interaction between plasma concentrations of the tricyclic antidepressant amitriptyline and the metabolism of the new antipsychotic risperidone was studied in 12 patients with chronic schizophrenia. Each patient received 3 mg risperidone twice a day for 28 days. Amitriptyline was coadministered at doses of 50 mg/day on day 15 and 100 mg/day on days 16 to 21. Amitriptyline did not significantly affect the mean plasma concentrations or pharmacokinetics of risperidone in schizophrenic patients or influence the antipsychotic fraction (the total concentration of risperidone and 9-hydroxyrisperidone, its primary and biologically active metabolite). These results suggest that risperidone dose need not be adjusted when coadministered with amitriptyline at doses up to 100 mg/day in schizophrenic patients.

Effects of metoclopramide and tropisetron on aldosterone secretion possibly due to agonism and antagonism at the 5-HT4 receptor

OBJECTIVE

Part of the prokinetic activity of metoclopramide can possibly be ascribed to agonist activity at 5-HT4 receptors. The 5-HT3 antagonist tropisetron is thought to act as an antagonist at 5-HT4 receptors. In the present study aldosterone secretion in response to the administration of these two drugs was explored to examine the role of the 5-HT4 receptor in aldosterone secretion.

METHODS

Following a single-blind, random design, ten normal male volunteers received one of the following regimens on three occasions, with at least 2-week intervals: metoclopramide 10 mg i.v.; tropisetron 5 mg by slow i.v.i., or; tropisetron by slow i.v.i., followed by 10 mg metoclopramide i.v.

RESULTS

In response to metoclopramide alone the mean plasma aldosterone level rose significantly to 149% of basal level and remained significantly elevated for the next 20 min. With tropisetron alone, there was a significant 37.8% drop at 60 min and the aldosterone levels remained low for the duration of the experiment. Metoclopramide reversed the decline mediated by tropisetron significantly at 30 and 90 min. Aldosterone levels after the latter regimen also did not differ significantly from baseline at any time period.

CONCLUSION

These results would suggest the existence of a tonic stimulatory influence of 5-HT via 5-HT4 receptors on aldosterone secretion, which could be augmented by metoclopramide and blocked by tropisetron. However, the effect of tropisetron per se should be interpreted with caution given the lack of a saline group.

The proportional cumulative area under the curve of paracetamol used as an index of gastric emptying in diabetic patients with symptoms of gastroparesis

1. The foreshortened 2 h method of measuring liquid gastric emptying (i.e. the proportional cumulative area under the curve of paracetamol) was utilized in diabetic patients in order to detect both gastroparesis and the influence of metoclopramide, a known prokinetic drug, on this condition. 2. Metoclopramide, 10 mg intravenously, caused a significant increase in the median PCAUC from 20 min onwards. 3. In this study delayed gastric emptying was defined as a %PCAUC without pretreatment lower than the 5% percentile at 40, 60 and 90 min for normal volunteers. According to this criterion seven of the 10 patients with clinical symptoms of gastroparesis and/or peripheral neuropathy had delayed gastric emptying. 4. The PCAUC method would therefore seem to be a reliable model for investigating gastric emptying in diabetics and the effects of various prokinetic drugs on this condition.

The influence of betahistine on the dynamics of the cutaneous hypersensitivity reaction in patients with grass pollen allergy

Histamine has been well documented as an immune modulator, but the dynamics of a number of histamine receptor agonists and antagonists have not been similarly established. The aim of this study was to determine the effect of betahistine (an H3-receptor blocker with partial H1- and H2-agonism) on the dynamics of the cutaneous hypersensitivity reaction. The skin blister technique was used to collect inflammatory cells after intradermal (i.d.) administration of grass pollen antigen, histamine and betahistine to 11 atopic volunteers. In this open, cross-over study, volunteers were randomly allocated to five treatment protocols i.e. (a) histamine 1 microgram i.d.; (b) betahistine 57, 114 and 285 micrograms i.d.; (c) i.d. grass pollen antigen; (d) (c) plus oral betahistine; (e) (c) plus oral betahistine, cetirizine, (H1-blocker) and cimetidine (H2-blocker). Blister fluid containing cells were collected on microscope slides at 6 and 24 h after i.d. injections. The areas of the wheal and flare and of induration were measured, respectively, at 0.25, and, 1, 6 and 24 h. Combined oral therapy with cetirizine, cimetidine and betahistine reduced the area of grass pollen-induced induration significantly at all time periods, but caused a significant increase in eosinophil and neutrophil vacuolisation during the late phase reaction. This did not occur with orally administered betahistine alone. Intradermal betahistine induced significantly more neutrophil and eosinophil vacuolization than histamine and, in contrast to the latter, also mediated a concentration-dependent late phase induration. The results of this study suggest that the H3-receptor regulates a feedback system in conjunction with that previously proven for the H2-receptor.(ABSTRACT TRUNCATED AT 250 WORDS)

The countering of diazoxide-induced vasodilatation by tenoxicam in normal volunteers

The effect of the nonsteroidal anti-inflammatory drug, tenoxicam, on diazoxide-induced lowering of standing diastolic blood pressure was explored in 10 normal volunteers. With diazoxide there was a significant fall in the 5-min standing diastolic pressure, i.e. a median drop of 15.5, 11.0, 9.5 and 7.0 mm Hg at 10, 35, 75 and 105 min, respectively, but with the tenoxicam-diazoxide regimen this pressure did not differ significantly from baseline at any time point. Tenoxicam did not modify the diazoxide-induced changes in blood glucose and plasma insulin. It may be that prostaglandins normally contribute to the lowering of peripheral vascular resistance, or that acutely-administered diazoxide enhances the release of vasodilatory prostaglandins.

Effects of glycopyrrolate on capsaicin-induced cough in normal volunteers treated with captopril

The effects of inhibition of angiotensin converting enzyme (ACE) and glycopyrrolate on cough caused by inhaled capsaicin were investigated in a double-blind, randomised cross-over study in twelve normal volunteers. The capsaicin challenge was performed before and 2 h after dosing with 75 mg captopril or matched placebo given orally, and 20, 40 and 60 min after giving 1 mg glycopyrrolate i.v. to each subject. Captopril and placebo did not alter the cough response when compared to baseline. Glycopyrrolate, however, caused a significant increase in the threshold sensitivity (D2) from baseline, and a significant decrease in the total cough response at 40 and 60 min both after captopril and placebo. The D2-baseline and D2-40 min after glycopyrrolate (mean SD), respectively, were 3.2 (1.0); 17.9 (4.2) after placebo and 2.5 (8.5); 23.6 (6.9) after captopril. Elimination of vagal influences implies attenuation of the effects of tachykinins but not those prostaglandins. We postulate that tachykinins, such as substance P, play a more important role than prostaglandins in capsaicin-induced cough. We conclude that the vagus is important in the capsaicin-induced cough reflex, but, as suppression of this reflex by glycopyrrolate was delayed, the relevant receptors are either poorly accessible peripheral receptors or they are located in the central nervous system.

Dexfenfluramine-induced prolactin release as an index of central synaptosomal 5-hydroxytryptamine during treatment with fluoxetine

Serotonin (5-HT) stimulates prolactin release. In the present study the ability of dexfenfluramine to increase serum prolactin was used as an index of central 5-HT function after acute and chronic pretreatment of volunteers with fluoxetine. Following a single-blind, random design, on each experimental day each volunteer received 60 mg dexfenfluramine taken with 250 ml water at zero time and no other treatment, or pretreatment with 40 mg fluoxetine at -8 h, or pretreatment with 20 mg fluoxetine daily for 14 days, or the dexfenfluramine alone 14 days after cessation of 14 days of fluoxetine treatment. There were no significant differences between the prolactin levels found after dexfenfluramine only, dexfenfluramine after a single dose of fluoxetine, and dexfenfluramine 14 days after cessation of fluoxetine treatment. However, baseline levels and those 3 and 4 h after dexfenfluramine administration were significantly lower after pretreatment for 14 days with fluoxetine compared to the other three regimens. At 5 h the levels were still lower, but not significantly so, as the prolactin level rose approximately 110% compared to the baseline and 4 h values. The reduction in the median basal serum prolactin level by almost two-thirds after 14 days of fluoxetine treatment suggests a decrease in 5-HT turnover. Furthermore, the delayed surge in prolactin release produced by dexfenfluramine with this regimen suggests 5-HT release from a less accessible pool or accumulation of fluoxetine in the neuronal cytosol and consequent competitive inhibition of 5-HT transport out of the nerve terminal.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of longterm cetirizine treatment on the cutaneous hypersensitivity reaction in patients with grass pollen allergy

In short-term studies cetirizine effectively reduces the early and late phases of the cutaneous hypersensitivity reaction. The aim of this study was to determine its long-term effects on both the vascular and cellular components of the reaction. The skin blister technique was used to collect inflammatory cells after intradermal administration of grass pollen antigen to 10 atopic volunteers. They were treated for 3 months with 10 mg cetirizine twice daily. Tests were done at baseline, before, and 7, 30 and 90 days after initiation of treatment. Blister fluid containing cells was collected on microscope slides at 6 and 24 hours. The area of induration was measured at 0.25, 1, 6, 10 and 24 h. Cetirizine significantly reduced the peripheral blood eosinophil count at 30 and 90 days (75% and 40% reduction respectively); there was no significant change after only one week's therapy. Eosinophil recruitment to and activation in the area of antigen administration were already maximally reduced after 7 days, namely a reduction of 54, 52 and 59% at 10 h, and of 55, 68 and 66% at 24 h, respectively, at 7, 30 and 90 days. The area of induration was significantly reduced after one week of therapy. There was a general tendency towards an increase in the reduction at 30 and 90 days, which reached significance only at the 24 h observation; there was a 24, 51 and 48% reduction from baseline at, respectively, 7, 30 and 90 days. The data clearly show a progressive reduction of induration as well as of cellular events over time.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of metoclopramide, ondansetron and granisetron on aldosterone secretion in man

The plasma aldosterone response following the administration of drugs with antagonist and agonist activity at Serotonin 3 and 4 (5-HT3&4) receptors has been examined in 9 healthy male volunteers receiving the following four treatments i.v. in a randomised, cross-over sequence: ondansetron 8 mg, granisetron 3 mg, metoclopramide 20 mg, and saline 20 ml. Metoclopramide significantly increased the mean plasma aldosterone level to 196% of basal level at 5 min. It rose to 234% at 15 min and remained at more than 185% of basal level for the duration of the experiment. The response to ondansetron and granisetron did not differ significantly from placebo. If dopamine antagonism is discounted, the results suggest that metoclopramide-induced aldosterone secretion results from its agonist activity at 5-HT4 receptors, although slow neuronal depolarization via an unidentified receptor remains a possibility. Antagonism at the 5-HT3 receptor plays no role, as the selective antagonist, granisetron, did not elicit a significant response. It seems unlikely that the 5-HT4 receptor is the second, low affinity binding site of ondansetron, unless it had no agonist activity at this receptor.

Effects of diclofenac on isradipine pharmacokinetics and platelet aggregation in volunteers

In this open, two-period crossover study in 18 healthy male volunteers, a single oral dose of 50 mg diclofenac was administered alone and on day 7 of multiple oral dosing of 5 mg b.i.d. isradipine to assess a possible pharmacokinetic interaction. The effect of these drugs on ex vivo platelet function was also determined. Serial blood samples were obtained over 12-hour periods on three occasions: after the single diclofenac dose; after the morning dose of isradipine on day 6 and after co-administration of both drugs on day 7 of steady-state isradipine administration. Additional samples were taken at 2 h post dose for determination of ex vivo platelet aggregation. Isradipine plasma concentrations were determined by a gas chromatographic method and diclofenac plasma concentrations by an HPLC method. The pharmacokinetic characteristics of diclofenac were unaltered during co-administration. The maximum plasma concentration of isradipine was increased 19.6% during co-administration from 5.06 to 6.05 ng.ml-1. This is not expected to be of clinical importance. Isradipine's apparent total body clearance and steady-state AUC remained unchanged. Ex vivo induced platelet aggregation was not affected by any of the treatments.

Effects of enhancement and antagonism of 5-hydroxytryptamine activity on the influence of metoclopramide on gastric emptying

This study examines the influence of the serotonergic system on the effect of metoclopramide on gastric emptying. Six subjects received the following pretreatments before metoclopramide and paracetamol: fluoxetine (5-HT uptake inhibitor); meterogoline (5-HT1 antagonist); pizotifen (5-HT2 antagonist) or methysergide (5-HT1 and 5-HT2 antagonist). One regimen consisted of metoclopramide (5-HT3 antagonist and 5-HT4 agonist) alone. Gastric emptying was measured by the mean cumulative fraction absorbed-time profiles of paracetamol. Methysergide/metoclopramide significantly delayed gastric emptying from 30 min onwards. Metoclopramide with either metergoline or pizotifen did not retard gastric emptying to the same extent, suggesting a greater influence with simultaneous 5-HT1 and 5HT2 blockade. Metoclopramide/fluoxetine caused a significant decrease in the fractional absorption of paracetamol at 5 min when compared to the metoclopramide regimen. It was assumed that the influence of metoclopramide was not optimal at this stage, therefore possibly indicating domination of 5-HT3 over 5-HT4 effects, resulting in gastric delay. It therefore seems as if all the 5-HT receptors present in the gut have a role to play in the control of gastric emptying.

A foreshortened method of measuring liquid gastric emptying in normal volunteers

The purpose of this study was to compare the cumulative fraction absorbed-time profile method of paracetamol with the shorter proportional area under the curve method of paracetamol by pretreating normal volunteers with cisapride, codeine and metoclopramide with and without neostigmine. Both methods are sensitive and comparable in defining early phase liquid gastric emptying, with the proportional area under the curve method having the advantage of providing the relevant information with a two-hour study period.

Influence of cisapride, metoclopramide and loperamide on gastric emptying of normal volunteers as measured by means of the area under the curve of the cumulative fraction absorbed-time profiles of paracetamol

The present study with paracetamol was designed to compare the effects of 40 mg cisapride, 20 mg metoclopramide and 4 mg loperamide given orally on gastric emptying under fasting conditions in normal volunteers. The well known bioavailability parameters of absorption and the area under the curve of the fractional absorbed time profiles up to 30 min were used as an index of gastric emptying. As reflected by the AUC of the fractional absorbed time profiles, it was concluded that pretreatment with cisapride speeded up the gastric emptying under fasting conditions. Tmax was the only normal bioavailability parameter that showed any significant change after cisapride treatment. Pretreatment with therapeutic doses of loperamide and metoclopramide did not significantly modify stomach emptying.

The effects of omeprazole-induced hypochlorhydria on absorption of theophylline from a sustained-release formulation

The present study was designed to investigate the effects of raised intragastric pH on the absorption of theophylline from a sustained-release formulation. Six healthy male volunteers participated in the cross-over randomised study and on one of two occasions were pretreated with 240 mg omeprazole, administered in three divided doses over the 22 h preceding the test. The sulphasalazine/sulphapyridine method of assessing oral-caecal transit time was implemented in order to assess upper bowel and colonic absorption. The mean fraction absorbed-time profile was calculated from serial serum theophylline concentration measurements by a modification of the Wagner-Nelson equation. During hypochlorhydria the mean oral-caecal transit time was 4.6 h, mean time to 90% absorption 6.8 h, and the percentage theophylline presumably to be absorbed from the colon 32.3. The corresponding values with normochlorhydria were, respectively, 3.8 h, 8.5 h, and 57.5%. The shorter oral-caecal transit time and lesser upper bowel absorption during normochlorhydria is postulated to result from motilin release due to duodenal acidification. Gastric hypoacidity resulted in significantly increased cumulative fractions of theophylline absorbed during a 3.5 h period, starting 0.5 h after breakfast. Possibly hypochlorhydria amplifies the increased motility which follows the intake of a meal, resulting in increased peristalsis and antiperistalsis, with more rapid drug absorption.

The absorption characteristics of six sustained-release theophylline preparations

Dosing intervals for sustained-release theophylline preparations depend on the rate of formulation absorption, the rate of elimination by the patient, and clinically acceptable fluctuations in serum concentration. A comparative study of intersubject variation in fraction absorbed-time profiles, a process-independent method of comparing rates of absorption, was performed with 6 sustained-release preparations in 6 healthy male volunteers. The sulphasalazine/sulphapyridine method of assessing orocaecal transit time was implemented so that upper gastrointestinal and colonic absorption could be estimated. Time until 90% absorption varied from 4.43 hours to 7.46 hours and the mean percentages of theophylline remaining to be absorbed from the colon were limited to between 7.5% and 29.7% with the various formulations. There was a great intersubject variability in the rate of theophylline absorption and also considerable differences among the volunteers in their formulation-to-formulation absorption profiles. Promotional literature depicting mean or group data masks this variability in absorption profiles. Because host factors related to gastro-intestinal physiology impose highly variable theophylline absorption profiles on sustained-release formulations, it is technically impossible to formulate a suitable once-a-day product for the majority of patients.

Effects of enhancement and antagonism of 5-hydroxytryptamine activity on metoclopramide-induced aldosterone secretion in man

This study examines the contribution of the serotonergic system to metoclopramide-induced aldosterone secretion. Six normal male volunteers, at 13 h, 9 h, and 2 h before the i.v. bolus of 10 mg metoclopramide, received the following pre-treatments in a single-blind cross-over randomized sequence: fluoxetine 20 mg, metergoline 6 mg, pizotifen 0.5 mg, or methysergide 2 mg. One regimen consisted of metoclopramide alone. Pizotifen and fluoxetine pre-treatment increased metoclopramide-induced aldosterone secretion significantly after 15 min, for the duration in the case of fluoxetine, and up to 90 min with pizotifen. The increase with metergoline was never significant, while methysergide had a negligible influence. Serotonin is postulated to play an intermediary role in acetylcholine-facilitated aldosterone release. The mechanism of fluoxetine-mediated serotonin increase is a re-uptake inhibition and that of pizotifen is suggested to be the elimination of an auto-inhibitory mechanism.

Inotropic effects of ranitidine

The purpose of this controlled study was to study the effect of cimetidine and ranitidine on the myocardium of 8 healthy male volunteers using systolic time intervals. Ranitidine caused a significant decrease in the QS2I, as from 40 min indicating a positive inotropic effect. There were no significant changes in heart-rate or blood-pressure. It is postulated that ranitidine, differing structurally from cimetidine, may have a higher affinity for H2-presynaptic receptors at the sympathetic myocardial junction resulting in an increase in noradrenaline and an increased inotropic effect.

The mean cumulative fraction absorbed-time profiles of paracetamol as an index of gastric emptying

The purpose of this study was to measure gastric emptying by using the cumulative fraction absorbed-time profiles of paracetamol. To evaluate the validity of the method as an index of gastric emptying, six healthy male volunteers were entered into an ethically approved trial using different regimens of cholinergic enhancing (i.e. metoclopramide and neostigmine) and blocking agents (i.e. atropine and pirenzepine) and the results were compared with the bioavailability (i.e. Cmax, Tmax, AUC) parameters of paracetamol as an index of gastric emptying. The cumulative fractional absorption of paracetamol appears to be a valuable index for the measurement of gastric emptying.

The effect of neostigmine on metoclopramide-induced aldosterone secretion after the administration of muscarinic antagonists in man

In this study the effects of neostigmine on metoclopramide-induced aldosterone secretion were examined in the presence of a relatively selective M1-antagonist, pirenzepine and of a non-selective muscarinic antagonist, atropine. Six normal male volunteers received metoclopramide, 10 mg i.v. on three different occasions, each study day being preceded by a day in which the intake of sodium and potassium was limited. The dosing was either metoclopramide alone or combined with either neostigmine and pirenzepine or with neostigmine and atropine. Serum aldosterone increased significantly with all three regimens. The highest levels were attained with the metoclopramide/neostigmine/pirenzepine regimen and those were significantly higher than those after metoclopramide alone and also, from 45 min onwards, from those after the metoclopramide/neostigmine/atropine regimen. The results of this investigation suggest that the metoclopramide-induced aldosterone secretion in humans is augmented by an accumulation of acetylcholine at the nerve-zona glomerulosa junctions and that the receptors mediating aldosterone secretion are of the M2-subclass of muscarinic receptors.

Fraction of theophylline in sustained-release formulation which is absorbed from the large bowel

In a cross-over study of six healthy male volunteers, 500 mg theophylline was administered either as plain tablets or in a sustained release preparation. On each occasion 2 g of non-enteric coated sulphasalazine was administered simultaneously as the time of appearance of sulphapyridine, the product of hydrolysis, in the blood provides an approximation of the oral--caecal transit time. The mean fraction absorbed--time profile was calculated from serial serum concentration measurements of theophylline by a modification of the Wagner-Nelson equation. The mean cumulative fraction of the dose absorbed following administration of the plain tablets was maximal at 3 h i.e. approximately 3 h ahead of the mean oral-caecal transit time, which was 5.9 h. Thus complete absorption occurred in the small intestine. With the sustained--release formulation, approximately only half of the dose was absorbed at the time the medication reached the large bowel i.e. at about 5.4 h. Absorption continued and at least 38% of the administered dose was additionally absorbed over the next 25 h. A reliable lengthened dosage interval is therefore possible with this particular sustained--release formulation.

Effect of neostigmine on metoclopramide-induced aldosterone secretion in man

This study examines the role of a neostigmine-induced increase in acetylcholine on the aldosterone stimulating effect of metoclopramide. Six normal male volunteers received the following three treatments in a cross-over randomized sequence: neostigmine, 0.5 mg s.c.; metoclopramide 10 mg i.v.; and neostigmine 0.5 mg s.c., followed by metoclopramide 10 mg i.v. Metoclopramide increased serum aldosterone significantly to 161% of basal level at 15 min. With neostigmine aldosterone levels peaked (129%) significantly at 30 min. In the presence of neostigmine, however, the metoclopramide-induced aldosterone response was blunted significantly. These results would suggest that presynaptic autoreceptors depresses the continued output of acetylcholine, thereby blunting the aldosterone responses to metoclopramide significantly.

Aldosterone response to metoclopramide is mediated through the autonomic nervous system in man

This study primarily examines the role of the autonomic nervous system in the aldosterone response to metoclopramide since there is conflicting evidence as to the involvement of a dopaminergic mechanism in this response. Six normal male volunteers in metabolic balance at 100 mmol sodium/day and 60 mmol potassium/day constant intake received metoclopramide, 10 mg i.v., on five different occasions. The dosing was either metoclopramide alone or combined with ganglionic, muscarinic, beta-adrenergic or calcium-channel blockade. Metoclopramide increased serum aldosterone significantly to 163.3% of basal level at 10 min. Atropine blunted this response and the 10 min level was significantly reduced to 116.03% of the basal value. The highest aldosterone levels were attained when metoclopramide was administered during a trimethaphan infusion and a peak of 292.8% of basal level occurred at 90 min. In the presence of atenolol, with or without nifedipine, the metoclopramide-induced aldosterone response was significantly greater at 15 min than with metoclopramide alone. The results of this investigation suggest that the aldosterone response to metoclopramide is mediated by acetylcholine released from post-ganglionic cholinergic nerve terminals, and that an adrenergic mechanism exerts a tonic inhibitory influence on aldosterone secretion in man.

Influence of food and reduced gastric acidity on the bioavailability of bacampicillin and cefuroxime axetil

The present study was designed to investigate the effect of food and of a raised intragastric pH on the bioavailability of two prodrug beta-lactam, antibiotics, namely bacampicillin and cefuroxime axetil. Six healthy volunteers participated in an intraindividual comparison of absorption of (a) prodrug, (b) breakfast, followed by prodrug, (c) breakfast, ranitidine and sodium bicarbonate followed by prodrug, and (d) ranitidine and sodium bicarbonate, followed by prodrug. All volunteers were dosed with both bacampicillin and cefuroxime axetil under the above regimens. The drug-free periods between trials were 7 days. Blood samples were obtained before and 20, 40, 60, 90, 120, 150, 180, 210 min and 4, 5, 6, 8 and 10 h after administration. The urine was collected for a period of 10 h after dosing with the antibiotic. An estimation of the relative bioavailability of the drugs under the various regimens was made by comparing the average areas under the serum concentration time curves and also the amounts recovered in the urine. Both food and reduced gastric acidity decreased the bioavailability of bacampicillin (as ampicillin) and these variables had an additive lowering effect on the AUC and percentage urinary recovery. Possibly this ester becomes partially hydrolyzed prior to absorption on raising the intragastric pH. Adsorption onto food components or complexing with proteins may also play a role in the reduced bioavailability of bacampicillin in the presence of food. In contrast, the absorption of the cefuroxime ester was enhanced postprandially. This may be rationalized in terms of delayed gastric emptying and gastrointestinal transit which allows more complete dissolution or prolonged residence at the most favourable site of absorption in the intestine.(ABSTRACT TRUNCATED AT 250 WORDS)

The effects of two combinations of a beta-blocker and a diuretic on diuresis in normal subjects

Combinations of a beta-blocker and a diuretic often produce a greater fall in blood pressure than does either drug alone. Furthermore, beta-blockers prevent an increase in plasma renin activity, thereby attenuating diuretic-induced potassium excretion and also the reduction in hypotensive response to the diuretic. This study was designed to compare the effects of the two fixed-dose combinations atenolol 100 mg plus chlorthalidone 25 mg (Tenoretic; ICI) and sotalol 320 mg plus hydrochlorothiazide 50 mg (Sotazide; B-M) on the pattern of diuresis and the biochemical composition of the urine in normal subjects. These preparations differ mainly in that the plasma half-lives of chlorthalidone and hydrochlorothiazide are 60 hours and 6 hours respectively; the former therefore accumulates when given once daily while the latter does not. These two preparations were found to have similar effects on the pattern of diuresis and the biochemical values. It is therefore concluded that the relationship between the serum chlorthalidone level and the fall in serum potassium level is in keeping with the flat dose-response curves for the thiazide and phthalimide diuretics.

Should young adults with sore throat be treated with antibiotics?

The diagnosis of streptococcal sore throat on clinical grounds remains a problem. In this study the clinical prediction in a group of young adults corresponded with laboratory findings indicative of a streptococcal (group A or non-A) infection in 23% of cases. The culture of throat swabs was of little value, as the only group A culture-positive patient did not show an antibody response, indicating a carrier state. In 5 cases a streptococcal infection was diagnosed on rising antibody titres only, as culture remained negative. The value of rising antibody titres as a diagnostic tool is also questioned, since they occurred more frequently in the healthy controls than in the sore-throat group. Antibiotic treatment for sore throat was rarely supported by laboratory findings in the young adult population studied.

The effects of labetalol and oxprenolol on blood lipids

Since a high risk of coronary heart disease is associated with high serum total cholesterol levels and low high-density lipoprotein (HDL) cholesterol levels, the effects of labetalol (Trandate; Allen & Hanburys) and oxprenolol (Trasicor; Ciba-Geigy) on blood lipids were studied. Eight normal volunteers, mean age 25,8 years, were involved in a randomized cross-over trial; all received each of the drugs for a 3-week period, separated by a wash-out period of 1 week. Both labetalol and oxprenolol reduced total serum cholesterol levels; these changes are statistically highly significant; Since the drugs had no significant effect on HDL cholesterol levels, the ratio of total cholesterol to HDL cholesterol was significantly decreased. Changes in triglyceride levels after both labetalol and oxprenolol administration were slight and did not reach statistical significance. The alpha-blockade caused by labetalol does no materially affect changes in blood lipid values brought about by beta-blockade. This study does not support previous reports, which have directed attention towards the possibility that, owing to alterations in lipid transport, adrenergic blocking agents might accelerate atherogenesis.