Pharmacological tolerance to alpha 1-adrenergic receptor antagonism mediated by terazosin in humans

Chronic administration of alpha 1-receptor antagonists is associated with loss of clinical efficacy, especially in congestive heart failure, although the mechanism is uncertain. To evaluate changes in venous alpha 1-adrenoceptor responsiveness during chronic alpha 1-adrenoceptor blockade, dose-response curves to phenylephrine and angiotensin II were constructed in 10 healthy subjects before, during, and after administration of terazosin 1 mg orally for 28 d. Terazosin initially shifted the dose-response curve of phenylephrine to the right, with a significant increase in ED50 for phenylephrine from a control value of 102 to 759 ng/min on day 1 of terazosin (P < 0.001). However, by day 28, the dose-response curve had shifted back towards baseline with an ED50 of 112 ng/min. After discontinuing terazosin, the ED50 for phenylephrine remained near the baseline value, indicating no evidence of supersensitivity to phenylephrine. There was no change in responsiveness to angiotensin II during the course of treatment with terazosin. Plasma terazosin concentrations were stable throughout the period of drug administration. The mean Kd of terazosin was estimated as 11 +/- 15 nM in the first few days of treatment. This study demonstrates that pharmacological tolerance to the alpha 1-adrenoceptor blocking action of terazosin occurs in man and may be responsible for loss in efficacy with chronic therapy.

Desensitization of nitrate-induced venodilation: reversal with oral N-acetylcysteine in humans

The objective of this study was to determine whether the dorsal hand vein could be used as a model to study tolerance to oral nitrates, and whether oral N-acetylcysteine (NAC) could reverse tolerance if present. Dose-response curves to nitroglycerin were constructed for 11 normotensive volunteers before and during treatment with a sustained-release formulation of isosorbide dinitrate, 80 mg, three times daily for 7 days and followed by concurrent treatment with NAC at a mean dose of 150 mg/kg/day, in divided doses, for 2 days. In separate studies, dose-response curves were constructed for seven normotensive volunteers before and after treatment with oral NAC at the same dose for 2 days. Nitroglycerin's Emax was significantly attenuated from 115 +/- 36 to 77 +/- 22% after treatment with isosorbide dinitrate alone (p < 0.009). Concurrent treatment with NAC reversed this decrease, as nitroglycerin's Emax of 108 +/- 26% during coadministration of isosorbide dinitrate and NAC was not different from its Emax in the control period. There was also no difference in the dose of phenylephrine required to cause 80% of maximal venoconstriction throughout the study. These studies demonstrate that smooth muscle tolerance to nitrates can be demonstrated in medium-sized veins in humans. In addition, high-dose oral NAC can reverse existing tolerance to oral nitrates in human veins. These results indicate that the dorsal hand vein compliance technique is a good model for the clinical investigation of tolerance to nitrates in humans.

Efficacy of preprocedural rinsing with an antiseptic in reducing viable bacteria in dental aerosols

This double-blind, controlled, cross-over, clinical study evaluated the effect of preprocedural rinsing with an antiseptic mouthrinse on the level of recoverable viable bacteria in an aerosol generated during a typical dental procedure. Eighteen subjects participated. Following 24 hours of abstention from all oral hygiene procedures, subjects received a 10-minute ultrasonic scaling of a randomly selected one-half of their mouth which served as the unrinsed control. They were then randomly assigned either antiseptic mouthwash or a control rinse and rinsed with 20 ml for 30 seconds, after which the remaining half mouth (experimental side) was scaled ultrasonically for 10 minutes. During each 10-minute scaling period aerosolized bacteria were collected on a sterile filter using a modified vacuum air-sampling device. Microbes captured on the sterile filter were quantitated by overlaying the filters onto trypticase soy agar, incubating the filters aerobically at 37 degrees C for 24 to 72 hours, and counting the resulting colony forming units (CFU). Preliminary experiments had confirmed that neither the collection method nor residual antiseptic mouthwash in the aerosol adversely affected the number of viable bacteria recovered from the filter. Rinsing with the antiseptic mouthwash produced a 94.1% reduction in recoverable CFUs compared to the non-rinsed control, while the control rinse produced a 33.9% reduction. The difference between the mouthwash and control was statistically significant (P < .001). This study indicates that preprocedural rinsing with an antiseptic mouthwash can significantly reduce the microbial content of aerosols generated during ultrasonic scaling and may have potential in-office use as part of an infection control regimen.

An assessment of the pharmacokinetics and pharmacodynamics of single doses of amlodipine in elderly normotensives

This study characterizes the single dose pharmacokinetic characteristics of the dihydropyridine calcium antagonist drug amlodipine in a group of 16 elderly subjects, aged 65 to 86 years (8 M:8 F). The most notable pharmacokinetic features were a prolonged terminal elimination half life of 48 +/- 16 hours and a delayed tmax of 7.3 +/- 1.3 hours. Consistent with the time to achieve peak plasma drug concentrations, there was a modest but significant reduction in blood pressure at 6-8 hours after dosing. Comparison of these results with those of published data for young subjects indicate not only a greater degree of intersubject variability but also a longer half life in the elderly, suggestive of reduced drug clearance, which may lead to higher plasma drug concentrations particularly at steady state.

Desensitization of beta-adrenoceptor- and prostaglandin E1 receptor-mediated human vascular smooth muscle relaxation

Regulation of beta-adrenoceptors in animal tissues and human cell cultures has been extensively described; on the other hand, relatively little is known about regulation of beta-adrenoceptors in human tissues in vivo. Both beta-adrenoceptors and the prostaglandin E1 (PGE1) receptors stimulate vasodilation. We wondered if prolonged infusion of isoproterenol or PGE1 would cause desensitization of smooth muscle relaxation and used the dorsal hand-vein compliance technique to investigate this question. After constructing a dose-response curve to either the beta-agonist isoproterenol or to PGE1 in a phenylephrine preconstricted vein, isoproterenol (271 ng/min), PGE1 (956 pg/min), or saline was infused for 4 h in separate experiments. There was no change in the ED50 or Emax for either isoproterenol or PGE1 after saline infusion. After a 4-h infusion of isoproterenol, the maximal vasodilator response to isoproterenol was significantly (p less than 0.01) attenuated from 61 +/- 33% to 19 +/- 10%, while the ED50 significantly increased (p less than 0.01) from a geometric mean of 37 to 197 ng/min. After infusion of isoproterenol, the mean maximum PGE1-induced venorelaxation of 129 +/- 29% was modestly but significantly (p less than 0.05) blunted to 96 +/- 35%, while the ED50 of PGE1 increased significantly (p less than 0.01) from a geometric mean of 81 to 398 pg/min. A 4-h infusion of PGE1 significantly (p less than 0.01) attenuated the maximum response to PGE1 from 73 +/- 35 to 28 +/- 16%. The maximal vasodilatory response to isoproterenol was also significantly blunted (p less than 0.05) from 62 +/- 35 to 42 +/- 41%, with no change in ED50.(ABSTRACT TRUNCATED AT 250 WORDS)

Vascular reactivity to phenylephrine and angiotensin II: comparison of direct venous and systemic vascular responses

The objective of this study was to determine the relationship between peripheral venous responsiveness (use of the dorsal hand vein compliance technique) and systemic vascular responsiveness (measurement of blood pressure changes) to phenylephrine and angiotensin II in humans. There was a significant correlation (r = 0.70, p less than 0.02) between the dose causing a 20 mm increase in mean arterial pressure and the dose producing half-maximal response in the hand vein (log ED50) for phenylephrine but not for angiotensin II. There was no correlation between the systemic responses to angiotensin II and phenylephrine, but there was a significant correlation (r = 0.70, p less than 0.02) between the log ED50 measurements for phenylephrine and angiotensin II in the hand vein experiments. These findings suggest that systemic and hand vein responsiveness to phenylephrine are similar. Consequently, in evaluating alpha-adrenergic receptor mediated responses, the dorsal hand vein compliance approach offers a satisfactory alternative to the use of systemic hemodynamic changes.

A simple purification method of squeezed krill for obtaining high levels of hydrolytic enzymes

The raw material originating from freshly caught Antarctic krill (E. superba) was processed by centrifugation and then immediately frozen. This squeezed fluid adjusted to pH 7 was subjected to spontaneous autolysis by storing at different temperatures (20-45 degrees C) and times (10-48 h). The autolyzed material resulted in 3 distinct phases after high speed centrifugation. The intermediate phase (water-phase) was collected and concentrated by membrane filtration. The high-molecular-weight substances (greater than 10,000 Daltons) were further purified by ion-exchange chromatography and eluted by a salt gradient. In this matter a bulk enzymatic material from krill can be efficiently obtained for further purification of different hydrolytic enzymes (peptide hydrolases/carbohydrases).

Proposal of Afipia gen. nov., with Afipia felis sp. nov. (formerly the cat scratch disease bacillus), Afipia clevelandensis sp. nov. (formerly the Cleveland Clinic Foundation strain), Afipia broomeae sp. nov., and three unnamed genospecies

On the basis of phenotypic characterization and DNA relatedness determinations, the genus Afipia gen. nov., which contains six species, is described. The type species is Afipia felis sp. nov. (the cat scratch disease bacillus). Afipia clevelandensis sp. nov., Afipia broomeae sp. nov., and three unnamed not associated with cat-borne disease. All but one strain (Afipia genospecies 3) were isolated from human wound and respiratory sources. All Afipia species are gram-negative, oxidase-positive, nonfermentative rods in the alpha-2 subgroup of the class Proteobacteria. They are motile by means of a single flagellum. They grow on buffered charcoal-yeast extract agar and nutrient broth, but rarely on MacConkey agar, at 25 and 30 degrees C. They are urease positive; but they are negative in reactions for hemolysis, indole production, H2S production (triple sugar iron agar), gelatin hydrolysis, esculin hydrolysis, and peptonization of litmus milk. They do not produce acid oxidatively from D-glucose, lactose, maltose, or sucrose. The major cell wall fatty acids are 11-methyloctadec-12-enoic (CBr19:1), cis-octadec-11-enoic (C18:1omega7c), and generally, 9,10-methylenehexadecanote and 11,12-methyleneoctadecanoate; and there are only trace amounts of hydroxy acids. The guanineplus-cytosine content is 61.5 to 69 mol%. A. felis is positive for nitrate reduction and is delayed positive for acid production from D-xylose, but it is catalase negative. A. clevelandensis is negative in all of these tests. A. broomeae is weakly positive for catalase production and acid production from D-xylose, but it is negative for nitrate reduction.

Phototherapy of seasonal affective disorder in an adolescent female

Seasonal affective disorder and its response to phototherapy has not been extensively studied in children and adolescents. In this case study, a 16-year-old girl with a 3-year history of seasonal affective disorder sought treatment. An A-B-A'-B study design demonstrates the remission of symptoms with phototherapy.

Use of red blood cells older than five days for neonatal transfusion

Sick neonates often require periodic small volume transfusions (10 mL/kg) to replace blood drawn for laboratory monitoring during their hospital stay. We use red blood cells (RBCs), stored as CPDA-1 whole blood, up to their expiration date, and are unaware of any clinical problems with this practice. We proceeded to confirm our clinical impression by reviewing the hospital records of 22 transfused neonates who received a median of 2.5 RBC transfusions (range 1 to 11) with a volume of 16 mL (range 5 to 38) each, and total volume of 60 mL (range 16 to 152). The RBCs were stored a median of 7 days (range 2 to 27). Following transfusion, there was an increase (P less than .05) in hemoglobin (mean 2.8 +/- 1.6 gm/dL [SD]) and hematocrit (9.0% +/- 4.7%). The bilirubin also rose (0.6 +/- 1.5 mg/dL, P less than .05), but this was not considered clinically significant. No significant change occurred in pH or bicarbonate. Paradoxically, RBCs over 10 days of age resulted in a fall in potassium (-0.9 +/- 0.8 mEq/L, P less than .01), but not below 3.4 mEq/L. We could find no evidence by clinical observation or laboratory indexes that small volume transfusion of RBCs more than 5 days old was deleterious to the newborns studied. By using RBCs up to their expiration date, the number of donor exposures and the potential risk of transfusion-transmitted diseases can be decreased.

Primary immune response to blood group antigens in burned children

Delayed hemolytic transfusion reactions (DHTRs) are generally attributed to an anamnestic immune response. Case reports of DHTRs due to a primary immune response are rare. Transfusion reactions occurring in patients on the pediatric burn unit from 1981 to September 1988 were reviewed, and additional information was obtained for patients for whom a DHTR was documented. Of 62 transfusion reactions, 11 were classified as a primary immune response (DHTR), with either a positive antibody screen, a positive direct antiglobulin test (DAT), or both. None of the 11 patients included in the study had been previously tranfused or pregnant. The average number of units transfused prior to antibody identification was 19. The average time elapsed between the first transfusion and antibody identification was 3.6 weeks. Anti-K and anti-E were the most frequently identified. Three patients had a decrease in hemoglobin (average 1.5 g/dL) and hematocrit at the time that a positive DAT was detected. Such changes could not be demonstrated for the remaining eight patients. The conclusion was that a DHTR may he caused by a primary immune response in burned children more often than expected, but DHTR signs and symptoms are often not apparent due to the complications of burn trauma.

Effects of methylphenidate on early adolescent growth

Thirty-one hyperactive adolescents treated with methylphenidate for at least 6 months demonstrated no significant deviation from expected height and weight growth velocities. In contrast to findings in prepubertal children, these results suggest that early adolescent growth is insensitive to methylphenidate.

Protection against membrane-mediated cytotoxicity by calcium and zinc

Injection of S. aureus alpha toxin or ultraviolet-inactivated Sendai virus into the mammary gland of lactating mice leads to cytopathic changes in the alveolar cells compatible with a breakdown of their permeability barrier. Simultaneous administration of Ca2+ or Zn2+ prevents such changes, as it does when added to alveolar cells in vitro. It is concluded that increased levels of Zn2+ (and under certain conditions of Ca2+) may exert a protective role that is clinically significant.

Familial defective apolipoprotein B-100: detection in the United Kingdom and Scandinavia, and clinical characteristics of ten cases

Familial defective apolipoprotein B-100 (FDB) is a recently identified, dominantly inherited genetic disorder, which leads to increased serum concentration of low density lipoprotein (LDL) cholesterol with reduced affinity for the LDL receptor. This disorder is associated with a G to A mutation in exon 26 of the apolipoprotein B (apo B) gene which creates a substitution of glutamine for arginine in the codon for amino acid 3500. We have searched for this mutation in 374 unrelated individuals with hyperlipidaemia from the United Kingdom, and in 371 unrelated individuals with a primary clinical diagnosis of atherosclerosis from the United Kingdom and Scandinavia. Ten individuals, 9 from the U.K. and 1 from Denmark, were identified. The frequency of the mutation was 3% in individuals classified clinically as having familial hypercholesterolaemia (FH) and 3% in individuals with type IIa hyperlipidaemia without FH, and was not found in patients with types IIb and III hyperlipidaemia. The mutation was rare in individuals with a primary clinical diagnosis of atherosclerosis. Plasma lipid levels and clinical characteristics of the ten patients identified in the present study are similar to those reported for heterozygous FH. Thus, in our study, FDB is associated with moderate to severe hypercholesterolaemia, and appears to be a serious disorder causing premature cardiovascular disease. Individuals with this mutation can be identified unambiguously using routine molecular screening techniques.

An AvaII polymorphism in the haptoglobin alpha gene (HPA)

Images

Biochemical and biological profile of a new enzyme preparation from Antarctic krill (E. superba) suitable for debridement of ulcerative lesions

A protease extract from Antarctic krill (E. superba) intended as a new enzymatic debrider for necrotic ulcers has been characterized by sodium dodecyl sulphate polyacrylamide gradient gel electrophoresis and fast protein liquid chromatography. The predominant enzymes in the preparation represent trypsin-like activity associated with three serine proteinases. In addition two carboxypeptidases A and B are present as cooperative enzymes for a more complete breakdown of complex proteinaceous substrates. Biological studies on a well-defined substrate (fibrin) originating from leg ulcers, demonstrated more effective degradation by krill enzymes than bovine trypsin, a common component in marketed enzymatic debriders. These findings support previously in vitro/in vivo studies in an animal model (rat) using excised rat skin as "necrotic" tissue.

Comparative field evaluation of the fluorescent-antibody test, virus isolation from tissue culture, and enzyme immunodiagnosis for rapid laboratory diagnosis of rabies

The rabies tissue culture infection test (RTCIT) and rapid rabies enzyme immunodiagnosis (RREID) were compared to the fluorescent-antibody test (FAT) with field specimens. At the French National Reference Center for Rabies, 15,248 specimens were analyzed by FAT and RTCIT, and 2,290 of those specimens were also tested by RREID; 818 other specimens were tested by FAT and RREID in 12 laboratories located in Africa, Asia, and Latin America. The sensitivities and specificities of RREID and RTCIT were comparable. This study showed that both tests can be used as backup procedures to confirm FAT. RREID is also strongly recommended for epidemiological studies and for laboratories which are not equipped for performing FAT.

Monoclonal antibodies to Mokola virus for identification of rabies and rabies-related viruses

Rabies and rabies-related virus strains were studied by using a panel of monoclonal antibodies directed against either nucleocapsid proteins or cell surface antigens of Mokola virus (Mok-3). Each strain was used in parallel to infect cultured cells and mice. Then, the patterns of reactivity of the different monoclonal antibodies were determined by the immunofluorescent-antibody staining procedure. On cells, the monoclonal antibodies differentiated fixed rabies virus strains (serotype 1) from rabies-related virus strains. The seven fixed strains (CVS, PV4, PM, Flury LEP and HEP, ERA, and SAD) reacted identically. The previous serotype groupings (serotype 2, Lagos-bat virus; serotype 3, Mokola virus; serotype 4, Duvenhage virus) established with anti-rabies monoclonal antibodies were confirmed, except for that of Lagos-bat Kindia, which appeared to be related to the African subtype of the Duvenhage serotype (Duv-2). Within the Mokola (Mok-1, -2, -3, and -5 and Umhlanga) and the Lagos-bat (Lag-1 and -2, Zimbabwe, Pinetown, and Dakar) serotypes, each strain appeared to be distinct. The African subtype of the Duvenhage serotype reacted differently from the European subtype. Within the Duvenhage serotype, subtypes Duv-4, -5, and -6 and Denmark reacted identically, while subtypes Duv-1, -2, and -3 and German Democratic Republic appeared to be distinct. The monoclonal antibodies specific for the cell surface antigens were also used in neutralization tests with all the strains. Two of them neutralized the infectivity of Mokola virus.

Ebastine: the effect of a new antihistamine on psychomotor performance and autonomic responses in healthy subjects

1. Ebastine, through its carboxylic acid metabolite has antihistamine (H1-receptor) activity in man. 2. We have examined in a single blind placebo controlled study the effects of 10 mg and 50 mg of ebastine on cardiovascular, autonomic and psychomotor function in healthy subjects. 3. Ebastine had no effect on blood pressure or heart rate and there was no evidence of any anticholinergic activity on circulatory reflexes or salivation. 4. Ebastine did not impair psychomotor performance as assessed by critical flicker fusion at either dose. 5. Ebastine 10 mg had no effect on sedation measured by visual analogue scale or direct questioning, however ebastine 50 mg did cause a modest increase in indices of sedation. 6. Ebastine did not have detectable sedative properties at the 10 mg dose where long-lasting antihistamine effects can be demonstrated.

The pharmacokinetics, antihistamine and concentration-effect relationship of ebastine in healthy subjects

1. The kinetics and effects of ebastine 10 and 50 mg were studied after oral dosing in healthy subjects. 2. The parent drug was extensively metabolised during the first pass to its carboxylic acid derivative, carebastine. 3. The pharmacokinetics of carebastine were linear over the dose range studied and the terminal elimination half-life was 10.6 +/- 2.6 and 12.5 +/- 1.9 h respectively after 10 and 50 mg of ebastine. 4. Antihistamine (H1-receptor) activity was examined with intradermal histamine (2 micrograms). Oral ebastine reduced the histamine wheal area for up to 24 h and also reduced subjective local pain. 5. Antihistamine activity correlated well with plasma levels of carebastine in individual subjects. 6. Ebastine appears to have potential as an antihistamine for once a day dosing.

Relationship between plasma prazosin concentration and alpha-antagonism in humans: comparison of conventional and rate-controlled (Oros) formulations

A single-dose comparative evaluation in young normotensive men of the plasma concentrations and alpha-adrenoceptor antagonism after conventional prazosin and a new slow-release formulation (Oros) is described. Whereas conventional prazosin (2 mg) produced a maximum reduction in erect blood pressure at 3 hours (80/46 mm Hg compared with 110/65 mm Hg with placebo), the lowest blood pressure of 94/48 mm Hg with Oros prazosin (5.5 mg) was not observed until 8 hours after administration. Twenty-four hours after Oros prazosin, prazosin was still detectable in plasma and erect blood pressure was reduced to 107/58 mm Hg compared with 110/71 mm Hg after placebo. alpha 1-Antagonism (assessed by the pressor responses to intravenous phenylephrine) was maximal, with a 4.8-fold shift in dose-response 24 hours after Oros prazosin, and persisted at least until 30 hours after administration, with a 2.3-fold shift. There were significant correlations between alpha 1-antagonism and plasma prazosin concentrations for both Oros and conventional prazosin. The slopes of these relationships were significantly different, but this is thought to be consistent with the differences in the rates of drug release from the two formulations. Overall this study provides further evidence in humans that the duration and extent of the alpha 1-antagonism and the blood pressure response reflect the plasma prazosin concentrations. Additionally these data suggest the potential suitability of this type of a slow-release formulation for single daily administration.

Immunological relationships between rabies virus and rabies-related viruses studied with monoclonal antibodies to Mokola virus

Specific monoclonal antibodies (mAb) were prepared against a rabies-related lyssavirus, Mokola virus. A strain isolated in the Central African Republic, Mok-3, was used as immunogen. After 3 fusions more than 90 hybridoma cultures secreting mAb were identified. According to their different patterns of reactivity against rabies and rabies-related viruses, 61 ascites fluids were obtained. The antibody class was IgM for 2 of them and IgG for 59. They were specific for one of the 4 major viral proteins, as determined by immunofluorescence, neutralization and immunoblotting tests. Their patterns of reactivity were determined against 6 different strains of rabies-related viruses: Lagos-bat virus from Nigeria (Lag-1) and the Central African Republic (Lag-2), Duvenhage virus from the Republic of South Africa (Duv-1) and Federal Republic of Germany (Duv-3), Mokola virus from Nigeria (Mok-1) and Cameroon (Mok-2) and a fixed strain of rabies virus, the challenge virus strain (CVS). According to their reactivities with these strains and the pattern of fluorescence, the mAb were classified into 11 different groups with intracytoplasmic fluorescence and 7 groups with cell surface fluorescence. A differential diagnosis of these lyssaviruses is possible in tissue culture using some of these mAb.

Pharmacokinetic and pharmacodynamic modelling of the alpha adrenoceptor antagonist doxazosin

1. The pharmacokinetic and pharmacodynamic profiles of intravenous and oral doxazosin were investigated in 6 normotensive volunteers. 2. The pharmacokinetics of i.v. and oral doxazosin were fitted simultaneously and independently. The parameters derived were in good agreement with a mean elimination half-life of 539 +/- 75 min, bioavailability of 0.65 +/- 0.11 and clearance of 140 +/- 26 ml/min. 3. Pharmacokinetic-pharmacodynamic modelling indicated that the sensitivities to oral and i.v. doxazosin in individual subjects were in good agreement. 4. Based on these findings it is unlikely that doxazosin metabolites contribute significantly to the pharmacodynamic profile of doxazosin.

Privatising residential care for elderly people: the geography of developments in Devon, England

The growth in numbers of very elderly people is becoming a trend in many Western societies. Often, these people may come to require some kind of assisted living environment. In Britain during the 1980s the overwhelming growth of residential accommodation has been in the private rather than the public sector. This has links with a number of other trends in health care and other sectors of the economy which are moving towards privatisation. The reasons for this are discussed and a case study of the county of Devon introduced. A survey of about one-quarter of all 450 homes in the county in mid-1984 revealed that they had important characteristics as small businesses. Countywide, a marked concentration of private residential homes has developed in some coastal 'holiday' locations. However, there have recently been changes in this pattern and growth of numbers of homes in some main towns also. There have been certain adverse reactions to the growth of homes and in a few areas, planning authorities have attempted to prevent the development of local concentrations of homes. This has been related to other policies elsewhere to prevent the concentration and ghettoisation of service-dependent groups. The nature and results of such planning policies are briefly considered. The paper addresses the overall questions of the type of care we wish to provide for our elderly people and whether privatisation of this aspect of health and welfare services is justified. This poses an important area of research for medical geographers interested in service delivery and aspects of equity in health care provision.

A pragmatic approach to the pressor dose-response as an index of vascular reactivity and adrenoceptor function in man

In clinical pharmacological studies, where it is not possible to describe the full dose-response curve, the construction of dose-response relationships ideally depends upon achieving a reproducible and readily measurable response for each dose administered. This study investigates in normotensive males the technique of dose-response analysis for the blood pressure and heart rate increases with constant infusions of incremental doses of vasoactive drugs, particularly catecholamines. Steady state responses could be adequately obtained using 5 min infusion periods (at each dose level) for noradrenaline and alpha-methyl noradrenaline. At least 7 min was required for phenylephrine and 8 min for isoprenaline. There was an approximate correlation between the time to achieve the steady state response and the half-life of the offset of the agonist effect. For interindividual comparisons it is desirable to compare steady state responses and so the time at each dose level will vary according to which agonist is being used. For intraindividual comparisons it may not be essential that steady state responses are achieved. For example, assessment of the effect of prazosin on the responses to phenylephrine, by calculation of dose ratios, indicated that 5 min dose intervals were adequate.

Clinical pharmacology of selective alpha blockers. Hemodynamics and effects on lipid levels

Selective alpha 1 antagonists decrease blood pressure by reducing elevated peripheral resistance and preserving normal cardiac reflexes. They have also been reported to usually decrease total cholesterol and low-density lipoprotein cholesterol levels, and, in some studies, to increase high-density lipoprotein cholesterol levels. Prazosin, a quinazoline derivative, is well tolerated and is not associated with chronic toxicity. Prazosin has been successfully used in the treatment of hypertension for more than 10 years. Its short plasma half-life requires twice-daily dosing. Although the hypotensive response to an initial dose of prazosin is usually greater than to subsequent doses during long-term therapy, the initial response is an accurate predictor of the hypotensive response in patients during long-term therapy. The vasodilatory action of prazosin is largely due to its blockade of vascular postjunctional alpha 1 receptors. The mechanism involved in its effect on lipid levels is currently under investigation and is an important consideration since hypercholesterolemia, as well as hypertension, is an independent risk factor for stroke and coronary heart disease. Reduction of blood pressure with conventional agents, such as beta blockers or diuretics, has not had the expected impact on coronary heart disease. However, since alpha 1 blockers may influence both hemodynamics and lipids, they warrant evaluation as first-line treatment of hypertension to confirm that they also have an effect on coronary heart disease.

The cardiovascular effects of trimazosin and prazosin in the rabbit

The cardiovascular effects of trimazosin, a quinazoline derivative similar in structure to prazosin, were investigated and compared with prazosin in the rabbit. Radioligand binding to cerebral membranes showed that trimazosin has roughly 100-fold less affinity for the alpha 1-adrenoceptor. This was further supported by its lower pA2 derived from phenylephrine contractile responses in isolated thoracic aorta preparations. Trimazosin is less extensively distributed and has a lower clearance from whole blood than prazosin although their whole blood elimination half-lives are comparable. In addition, although it is a less potent alpha 1-adrenoceptor antagonist in vivo, its peripheral vascular depressor effect tends to be greater than prazosin. Trimazosin at the dose used and under the conditions of study did not reverse the peripheral pressor effect of angiotensin II or B-HT920 but at higher concentrations, unlike prazosin, it relaxed the K+ contracted thoracic aorta. In addition, following pharmacological autonomic blockade and treatment with prazosin in vivo, trimazosin caused a further depressor response. A similar though shorter lasting non-alpha 1-receptor mediated action was also observed with prazosin. 1-Hydroxytrimazosin (CP23445), the major metabolite of trimazosin in man, showed little affinity for either the alpha 1- or alpha 2-adrenoceptor from radioligand binding studies. In addition to alpha 1-adrenoceptor antagonism, trimazosin may exert an additional direct vasodilator effect in rabbits.

[Role of ketotifen in the immunotherapy of atopic asthmatics]

The place of KETOTIFEN in the immunotherapy for atopic asthmatic patients (confirmed by cutaneous test and RAST) has been determined by a study conducted on 48 patients divided into two randomly selected parallel groups. Group one received 2 mg/d. Ketotifen treatment together with a desensitization. Group two: only had a specific hyposensitization treatment. The study was contacted over a period of 18 weeks and showed that the number of local reaction in group one was half as numerous as in group two. In conclusion, KETOTIFEN may be practised an immunotherapy to house dust and acarians, without any difficulties, and with a fast progression.

The pharmacokinetics of doxazosin in elderly normotensives

The pharmacokinetics of doxazosin were studied in 12 normotensive elderly volunteers aged 62-89 years. There was marked inter-individual variability in all the parameters derived but the disposition of doxazosin was similar in both sexes. These results were compared to those of a group of young normotensive volunteers aged 23-39 years studied previously under comparable conditions. The volume of distribution increased significantly with age although the bioavailability and clearance were not significantly different in the two groups. These results suggest that age is unlikely to influence the disposition of doxazosin to a clinically significant extent.

Proteases of Antarctic krill--a new system for effective enzymatic debridement of necrotic ulcerations

The Antarctic krill (Euphausia superba) possesses an "over-dimensioned' digestive system, which is of vital importance for the survival of this euphaucean shrimp in the extreme marine environment. The isolated enzymes contain a well-balanced mixture of both endo- and exopeptidases, assuring fast and complete breakdown of proteinaceous material. These unique properties have now been shown to be extremely valuable for the effective removal of necrotic debris, fibrin or blood crusts in vitro. Therefore the krill enzymes should be considered as an important resource in the future management of necrotic wounds.

Racial differences in drug responses--a comparative study of trimazosin and alpha 1-adrenoceptor responses in normotensive Caucasians and West Africans

The possible racial differences in alpha 1-adrenoceptor responsiveness and the blood pressure and heart rate responses following alpha 1-adrenoceptor antagonism with trimazosin have been investigated in matched groups of six Caucasians and six Nigerians. There were no significant differences between the racial groups in the blood pressure and heart rate responses to oral (200 mg) and intravenous (100 mg) trimazosin. alpha 1-adrenoceptor responsiveness was similar in both groups after placebo and following both active treatments. There were only minor pharmacokinetic differences with the Caucasians having a larger volume of distribution, and a longer terminal elimination half-life for the metabolite, 1-hydroxy-trimazosin. These results suggest a similarity in peripheral vascular alpha 1-adrenoceptor mechanisms and show no major significant racial differences in the pharmacokinetics and pharmacodynamics of trimazosin.

Clinical pharmacology and therapeutic role of prazosin and related alpha-adrenoceptor antagonists

Prazosin is a quinazoline derivative, which lowers blood pressure by selective alpha-1-receptor antagonism. It has been found that, for similar decreases in blood pressure, prazosin causes less reflex tachycardia than non-selective alpha blockers or direct vasodilators, and that it is as efficacious as other conventional antihypertensive agents (alpha-methyldopa, hydralazine, beta blockers, etc.) in controlling severe hypertension. Prazosin causes a dose-related decrease in blood pressure in humans; twice-daily dosing is sufficient for 24-hour blood pressure control. Prazosin in combination with other drugs has also been shown to control blood pressure effectively, and it has been associated with relatively few side effects. Other agents with selective alpha-1-receptor-blocking activity are under investigation: these include doxazosin, trimazosin, terazosin, and alfuzosin.

Clinical pharmacological studies with doxazosin

The clinical pharmacology of doxazosin is reviewed from studies in normotensive young (21-39 years) and elderly (62-89 years) subjects following oral (2 mg) and intravenous (1 mg) administration. In young subjects the mean bioavailability was 65% and the mean terminal elimination half-lives were 9.5 and 10.5 h following acute intravenous and oral administration respectively. These parameters were similar in the elderly with bioavailability of 69% and half-lives of 8.8 and 11.9 h. The apparent volume of distribution and clearance were significantly higher in elderly (1.7 1 kg-1 and 140 ml min-1) than in young subjects (1.01 kg-1 and 83 ml min-1). In both groups blood pressure reductions were most marked in the standing position and the maximum effect did not occur until 5-6 h, even after intravenous administration. The blood pressure reduction produced by doxazosin was associated in the young with a significant increase in heart rate to 108 beats min-1 (placebo, 82 beats min-1) but this increase was significantly attenuated in the elderly at 91 beats min-1 (placebo, 77 beats min-1). Pressor response studies in the young subjects confirmed the alpha 1-adrenoceptor antagonist activity of doxazosin with significant rightward shifts of the dose-response curves for the selective alpha 1-adrenoceptor agonist phenylephrine. Using the technique of concentration-effect analysis, both the degree of alpha 1-adrenoceptor antagonism and the hypotensive effect can be correlated with the concentration of doxazosin in the 'effect compartment'.(ABSTRACT TRUNCATED AT 250 WORDS)

The pharmacokinetics of bucindolol and its major metabolite in essential hypertension

The pharmacokinetics of bucindolol and its major metabolite, 5-hydroxybucindolol, have been studied in eight patients with mild/moderate hypertension. The mean terminal elimination half-life of bucindolol following acute oral dosing was 8.0 +/- 4.5 h, while the elimination half-life of the metabolite was 0.15 +/- 0.13 h. Because of the large intraindividual variation in the pharmacokinetics of the drug and metabolite, no significant differences in the kinetics following acute or chronic dosing were seen. There was very wide interindividual variability in the pharmacokinetics of bucindolol and 5-hydroxybucindolol, and large interindividual differences in the metabolic profiles as assessed by the areas under drug and metabolite concentration-time curves. This latter observation might be associated with a genetic polymorphism of drug metabolism.

Pharmacokinetic and pharmacodynamic studies with two alpha-adrenoceptor antagonists, doxazosin and prazosin in the rabbit

The cardiovascular effects of doxazosin, a quinazoline derivative related to prasozin were investigated and compared to prazosin in the rabbit. Radioligand binding studies using rabbit cerebral membranes showed that both doxazosin and prazosin were roughly equipotent at displacing [3H]-prazosin from specific binding sites. However, the lower pA2 value for doxazosin at alpha 1-adrenoceptors in isolated thoracic aorta preparations suggests a lower potency compared to prazosin. The dose-related pressor effects of intravenous phenylephrine were used to assess vascular alpha 1-adrenoceptor antagonism in vivo. There was a close agreement between alpha 1-adrenoceptor antagonist potency and maximum hypotensive effects with both doxazosin and prazosin. The alpha 1-adrenoceptor antagonist effects of doxazosin were more prolonged than those of prazosin. Studies using either radioligand binding or pressor responses to B-HT 920 showed that doxazosin did not show any significant affinity for the alpha 2-adrenoceptor. Similarly, no direct vasodilator effects were observed either in animals administered angiotensin II or in isolated thoracic aorta spiral strip preparations contracted with potassium. Doxazosin has a longer terminal elimination half-life than prazosin. The pharmacokinetics of doxazosin were linear over the dose range examined. Following pharmacological 'autonomic blockade' and treatment with prazosin, doxazosin did not cause any further fall in blood pressure. These observations suggest that doxazosin, like prazosin, appears to exert its hypotensive action through alpha 1-adrenoceptor antagonism. The prolonged fall in blood pressure and well sustained alpha 1-adrenoceptor antagonism after doxazosin raise the possibility of an active metabolite which also has alpha 1-adrenoceptor blocking properties.

Clinical pharmacokinetics of prazosin--1985

Prazosin is a selective alpha 1-adrenoceptor antagonist which is useful alone or in combination for the treatment of hypertension and heart failure. Unlike many other antihypertensive drugs, the action of prazosin appears to be closely related to its concentration in plasma or whole blood. Prazosin is variably absorbed, is subject to first-pass metabolism, and is eliminated almost entirely as metabolites of much lower hypotensive activity than the parent drug. Prazosin is highly bound to plasma and tissue proteins. The influences of renal, hepatic and cardiac disease on the disposition of prazosin are reviewed, as are the effects of pregnancy and ageing. The optimum use of prazosin in clinical practice depends on an understanding of the pharmacokinetic properties of the drug.

The effect of cimetidine on the pharmacokinetics, pharmacodynamics and alpha 1-adrenoceptor responsiveness of trimazosin in man

The effect of cimetidine treatment on the pharmacokinetics and pharmacodynamics of single doses of trimazosin was studied in 6 normotensive volunteers. Co-administration of cimetidine did not significantly affect the overall magnitude of the hypotensive effect of trimazosin. However, the time profile of the blood pressure response was significantly modified particularly with attenuation of the delayed component. Co-administration of cimetidine did not alter alpha 1-adrenoceptor antagonism by trimazosin. There was no significant change in the clearance and volume of distribution of trimazosin but there was a significant reduction in the area under the concentration-time curve for the metabolite, 1-hydroxy-trimazosin. The reduction in the AUC of 1-hydroxy-trimazosin corresponds in time with the attenuation of the delayed hypotensive response. This is consistent with the suggestion that the delayed hypotensive response is related to an active metabolite, probably 1-hydroxytrimazosin.

The alpha adrenoceptor antagonist properties of idazoxan in normal subjects

The imidazoline derivative idazoxan, which has been shown to be a potent, selective alpha 2-adrenoceptor antagonist, was injected intravenously to eight men with normotension. There was a transient small increase in blood pressure and a decrease in heart rate within 20 min of injection, with a slight increase in plasma norepinephrine levels. These effects are consistent with antagonism of prejunctional alpha 2-adrenoceptors. In response to infusions of the relatively selective alpha 2-adrenoceptor agonist alpha-methylnorepinephrine, the pressor dose-response curve shifted to the right with idazoxan. These data provide evidence for receptors with alpha 2-adrenoceptor characteristics on resistance vessels in man. In vitro platelet aggregation studies provide further evidence of selective alpha 2-adrenoceptor antagonism by idazoxan, with greater potency and affinity than alpha-yohimbine. These observations are consistent with both pre- and postjunctional peripheral alpha 2-adrenoceptors in man and provide further support that idazoxan is a selective alpha 2-adrenoceptor antagonist.

False aneurysm of a left ventricular stab wound for left vent during extracorporeal circulation--case report

The left ventricular apical stab wound had been used for instrumentation and venting since 1923. Despite the frequent use of this myotomy, only a few complications and even fewer operative corrections have been reported. One of these complications is a false aneurysm, its reported etiology being infection or suture failure. In this case we describe a case of left ventricular false aneurysm formation most likely due to suddenly increased intrathoracic pressure, 6 months after coronary artery bypass grafting. Evidence for likely causes, such as infection, suture failure or poor myocardial quality, was not found. As etiology we suspect an acute elevation of ventricular pressure superimposed upon poorly regenerated myocardium.

Trimazosin in normotensive subjects

Oral and intravenous trimazosin, a quinazoline derivative, resulted in a significant reduction in blood pressure of normal subjects, particularly when the subjects rose from a supine position to standing. This hypotensive effect was maximal between 4 and 6 hr after dosing and was accompanied by a significant increase in heart rate. The responses to intravenous infusions of phenylephrine indicated that trimazosin had significant, selective, peripheral alpha 1-antagonist properties. Kinetic analysis showed oral bioavailability of 63%, a clearance rate of 66 ml/min, and a terminal elimination t1/2 of approximately 3 hr. The correlation between drug levels and hypotensive effect was significantly improved by inclusion of the concentrations of trimazosin's major metabolite, 1-hydroxy-trimazosin (CP 23445), particularly for the period of maximum effect. Our data show that acute administration of trimazosin is associated with a fall in blood pressure, an increase in heart rate, and a significant degree of alpha 1-antagonism and that the overall hypotensive effect may in part be mediated by an active metabolite. It seems 1-hydroxy-trimazosin is a likely candidate for this role, but it is not clear whether this metabolite also has significant alpha-adrenoceptor antagonist properties.

[Intrarenal localized renorenal collaterals in dogs after ligation of the principal arterial branch]

In 7 kidneys of 6 dogs one of the main stem of the renal artery was ligated. The development of the renorenal collaterals could be followed in 5, as two dogs died after the operation. In all cases intrarenal collaterals could be demonstrated, even in the postoperative dead dogs. The vessels responsible for the collateral circulation are performed interarterial anastomoses, belonging to the extra-glomerular arterial system. From the results of these and former experimental studies it can be concluded, that the renal artery of the dog when entering the renal sinus cannot be regarded as an anatomic, but at most as a functional end artery.

The incidence of tinea versicolor in central Sweden

In a survey of 3302 people in an area of central Sweden, tinea versicolor was diagnosed in 0.5% of males and 0.3% of females; all those infected were adults. Tinea versicolor is much less common in Sweden than in the tropics.