Does intention-to-treat analysis answer all questions in long-term mortality trials? Considerations on the basis of the ANZ trial.

AIMS: Intention-to-treat (ITT) analyses are the gold standard in endpoint analyses of randomized clinical trials. Valuable information, however, may be lost in this approach as the actual time on trial medication is not accounted for in patients who withdraw early. Since compliance per se can be a prognostic factor and the actual treatment time is a variable likely to influence clinical outcome, this information should be added to an ITT analysis concept. Thus, the aim is to elucidate the influence of actual treatment time on the results of ITT analysis using available data from a well-conducted, large-scale clinical trial. METHODS AND RESULTS: The ANZ trial, a carvedilol study in heart failure, is characterized by a considerable number of early withdrawals in the carvedilol group. Using the ANZ trial database, the percentage of withdrawals was calculated as well as the number of days on treatment. Fourteen out of 21 deaths (67%) in the carvedilol group occurred after discontinuation of carvedilol. At the time of death, 14 out of 29 (48%) patients in the placebo group had withdrawn from treatment. Mean time of patients on medication who withdrew and died later were 301 days for placebo, but only 204 days for carvedilol. We performed a conventional ITT analysis, and an ITT-based Cox-proportional hazards model (modified ITT) in which the actual time on trial medication was entered into the model as an explanatory variable. The risk ratio in conventional ITT analysis was 0.71 (95% confidence interval (CI) 0.41 to 1.24, p = 0.228) and 0.50 (95% CI 0.28-0.90, p < 0.001 ) in modified ITT analysis. CONCLUSIONS: Incorporation of the actual treatment time substantially influences the result of this exemplary ITT analysis. The resulting risk ratio is clearly in accordance with clinical implications and in close agreement with those of other beta-blocker trials in heart failure. Entering the actual treatment time into a Cox-proportional hazards model as an explanatory variable is reasonable if not necessary from a clinical point of view and thus may strengthen the validity of ITT analysis.

[The effect of carvedilol on contrast echocardiography in comparison to metoprolol in conscious dogs]. / Wirkungen von Carvedilol auf das Kontrastmittel-Echokardiogramm im Vergleich zu Metoprolol bei wachen Hunden.

This animal study was to demonstrate the effect of the betablockers carvedilol (CAS 72956-09-3) and metoprolol (CAS 37350-58-6), respectively, on myocardial perfusion which was quantified by the use of contrast echocardiography. Each of four experimental schemes were applied consecutively to each of six dogs. They were pretreated with oral administration of either carvedilol (2 mg/kg b. wt.) or with metoprolol (4 mg/kg b. wt.), or received no premedication. 2 h later the contrast agent BY963 (0.03 ml/kg)--a new transpulmonary contrast agent for sonography, based on phopspholipid stabilized microbubbles--was injected intravenously three times at intervals of 2.5 min 5 min in advance and 7.5, 10, 20, and 30 min following the first injection 60 digitized echocardiography images were recorded during a time period of each 2.9 s. From these images average grey-scale values at predetermined points of time were derived. Time-intensity curves of the region of interest of the interventricular septum were computed. Changes in intensity were calculated by baseline subtraction. Myocardial opacification was observed with all injections of the contrast agent in each dog. The effects were marked and no non-responder was observed. There was no return to baseline grey-scale values within the observation period (30 min). Pretreatment with carvedilol was followed by a more pronounced contrast intensity than was with metoprolol. All administrations were well tolerated. No changes in ECG were observed. Heart rate decrease was marked on metoprolol. Blood pressure dropped to a greater extent on carvedilol compared to metoprolol.

Local drug delivery via transvascular injection.

BACKGROUND: In this experimental series we tested drug distribution and systemic leakage using local drug delivery with a new transvascular injection system. METHODS: Porcine femoral and carotid arteries (n = 56) underwent local drug application with a new 5 French (Fr) over-the-wire needle-injection catheter system (NIC) using three needles. A radioactive indicator [C14-Carvedilol, 2.0 milliliter (ml); 0.03 milligram (mg)] was injected in two carotid and two femoral vessels in parallel. Serial blood withdrawal was performed thereafter. After randomization to different explantation times, the vessels, perivascular tissue, liver and spleen were removed [0.5, 1, 1.5, 3 and 4 hours after injection, respectively]. Radioactivity was determined in a scintillation counter or with autoradiography. The indicator amount was calculated in relation to total drug amount (100%). RESULTS: Use of the NIC caused vessel texture alteration in non-diseased porcine vessels, seen as vessel wall penetration and perivascular edema. After single injection the maximum of the indicator was found in perivascular tissue 0.5 hours at the application site (carotid perivascular tissue: 7.48%; femoral perivascular tissue: 2.56%). Thereafter, radioactivity in the artery increased and perivascular content declined. The maximum in femoral arteries (1 hour; 1.96%) occurred earlier and was significantly lower compared to carotid arteries (2 hours; 7.75%). Four hours post-injection, 1.4% of total drug amount was detectable in the carotid arteries and 0.6% was detected in the femoral arteries. Systemic content was measured after C14-Carvedilol application with a maximum in serum of 28% (10 minutes), liver 30% (0.5 hour) and spleen 0.6% (0.5 hour). After 3 hours, still 5% of the indicator was still measureable in the serum and liver and less than 0.1% was measurable in the spleen. LDD with the NIC system is dependent on the vascular anatomy. The data indicate redistribution from perivascular to vascular space thus allowing a prolonged vascular and perivascular drug delivery. The amount deliverable is lower than expected due to substantial systemic drug contamination with this catheter.

Effects of naftopidil on some urodynamic parameters and arterial blood pressure in comparison with prazosin in conscious rats.

Naftopidil, an alpha 1-adrenergic antagonist, was orally tested in comparison with prazosin, in a rat cystomanometric model to evaluate the effect on the bladder volume capacity (BVC), the micturition pressure (MP) and the mean arterial blood pressure (MAP), contemporaneously recorded to evaluate the selectivity of action. Naftopidil induced a clearcut increase of BVC and a decrease of MP without lowering MAP at 6.25 mg kg-1 p.o.. Prazosin was inactive on BVC, decreased MP and induced a significant decrease of MAP at 1.56 mg kg-1 p.o. Naftopidil could offer an advantage when compared with prazosin.

Effect of 17beta-estradiol-bisphosphonate conjugates, potential bone-seeking estrogen pro-drugs, on 17beta-estradiol serum kinetics and bone mass in rats.

In order to target 17beta-estradiol directly at bone we synthesized three 17beta-estradiol-bisphosphonate conjugates (E2-BPs) with different esterase-sensitive linkers between both molecular moieties. The systemic administration of these compounds should result primarily in local estrogenic effects on bone with no or negligible systemic hormonal effects. Only if a considerable margin exists between the doses required for inhibition of bone loss and those for systemic hormonal effects can such a pro-drug be considered acceptable for patients refusing systemic estrogen replacement therapy for several reasons. The conjugates were tested in vitro for their 17beta-estradiol release in rat serum and in vivo for their local and systemic effects in rats: in vitro, the conjugates expressed cleavage resistance, low cleavage (4.8%), or high cleavage (33.1%) within 48 hours of incubation. The conjugate with the low-cleavage doubled 17beta-estradiol serum half-life (3.78 hours) whereas the high-cleavage conjugate resulted in approximately four times higher serum half-life (8.36 hours) when compared with free 17beta-estradiol. In ovariectomized rats, bone loss was optimally prevented by 50 nmol/kg/day of 17beta-estradiol when administered S. C. over a period of 5 weeks, and protection against uterine atrophy was achieved at doses as low as 5 nmol/kg/day. The cleavage-resistant conjugate was ineffective in preserving bone and uterus in doses ranging from 5 to 150 nmol/kg/day. The other two E2-BPs revealed a dose-dependent inhibition of bone loss which was paralleled by the respective uterus weight with a dose range of 1.5-150 nmol/kg/day being fully effective in a range similar to 17beta-estradiol alone. The higher sensitivity of the uterus versus bone to protective estrogenic effects (1:10) was abolished by the conjugates. We conclude that E2-BPs containing esterase-sensitive linkers failed to act as bone-seeking pro-drugs expressing primarily local effects on bone without systemic effects.

Influence of heparin and systemic lysis on coronary blood flow after reperfusion induced by the novel recombinant plasminogen activator BM 06.022 in a canine model of coronary thrombosis.

OBJECTIVES: We sought to evaluate whether anticoagulation by an intravenous heparin infusion prevents deterioration of coronary blood flow restored by the novel recombinant plasminogen activator BM 06.022, and to compare the effects of profound fibrinogenolysis with those of an intravenous bolus injection of heparin. BACKGROUND: Recent clinical studies indicate that heparin appears to be effective in reducing reocclusion when combined with recombinant tissue-type plasminogen activator (rt-PA), but that heparin is associated with an increased bleeding incidence. Therefore, the need for heparin has to be critically evaluated in the development of BM 06.022. METHODS: BM 06.022 is an unglycosylated variant of human tissue-type plasminogen activator. Thrombus formation in anesthetized open chest dogs was induced by electrical injury. Left circumflex coronary artery blood flow was monitored for 4 h using an electromagnetic flow probe. Twenty dogs were randomized to receive intravenous heparin (100 IU/kg bolus plus 100 IU/kg per h) in group B or saline solution in group A before an intravenous bolus injection of 200 kU/kg (= 0.34 mg/kg) BM 06.022 1 h after thrombus formation. Another 14 dogs were randomized to receive a single intravenous bolus injection of 200 IU/kg heparin plus 200 kU/kg BM 06.022 in group D or saline solution plus 1,000 kU/kg BM 06.022 in group C. RESULTS: In the absence of a systemic lytic state, heparin infusion prolonged (p < 0.05) the cumulative patency time (sum of time intervals during which the coronary artery was patent) to 204.3 +/- 7.4 min (group B) compared with 34.6 +/- 10.8 min with saline solution (group A), and increased (p < 0.05) the area under the curve for coronary blood flow versus time (AUCFlow) to 34.0 +/- 3.4 ml.h.min-1 compared with 7.7 +/- 4.6 ml.h.min-1. Profound fibrinogenolysis after administration of 1,000 kU/kg BM 06.022 (group C) and a single intravenous heparin injection (group D) did not differ in their effects on the cumulative patency time (182 +/- 30.3 vs. 177.5 +/- 25.4 min) and AUCFlow (36.0 +/- 10.3 vs. 30.5 +/- 4.8 ml.h.min-1), but these values were improved (p < 0.05) compared with those obtained after administration of saline solution plus 200 kU/kg BM 06.022 (group A). CONCLUSIONS: In the absence of a systemic lytic state, intravenous heparin is required as an adjunct to BM 06.022 to maintain coronary blood flow in dogs.

Norepinephrine-induced changes in rat heart function, metabolism, and weight are antagonized by carvedilol.

One aim of our study was to characterize in intact rats the pharmacologic effects of carvedilol. After 3 days of continuous intravenous (i.v.) infusion of carvedilol (0.5 mg/kg/h), the positive chronotropic and inotropic effects of i.v. bolus injections of isoproterenol (0.1, 0.3, and 1 microgram/kg) and phenylephrine (3, 10, and 30 micrograms/kg), respectively, were measured and compared with those obtained in rats that received a continuous i.v. infusion of 0.9% NaCl, prazosin (0.1 mg/kg/h), and propranolol (0.5 mg/kg/h). The chronotropic response to isoproterenol was less blunted in carvedilol-treated animals than in propranolol-treated animals. The pressure response to phenylephrine was attenuated only moderately. Thus, carvedilol had beta-receptor blocking actions on intact rat heart that were similar to but not as pronounced as those of propranolol. Because it reduced diastolic aortic pressure (DAP) and left ventricular systolic pressure (LVSP), it also had a moderate vasodilating effect. Carvedilol (continuous i.v. infusion of 0.25 and 0.5 mg/kg/h) antagonized the effects of norepinephrine (NE, i.v. infusion of 0.2 mg/kg/h for 3 days) on heart function and heart weight in a dose-dependent manner. It also attenuated markedly the norepinephrine (NE)-induced increase in the activity of cardiac glucose-6-phosphate dehydrogenase (G-6-PD), the first and rate-limiting enzyme of the oxidative pentose phosphate pathway (PPP), although a 37% stimulation persisted.

Differential fibrinolytic properties of the recombinant plasminogen activator BM 06.022 in human plasma and blood clot systems in vitro.

The effects of the unglycosylated recombinant plasminogen activator BM 06.022, consisting of the kringle 2 and protease domains of tissue-type plasminogen activator (t-PA), on clot lysis were evaluated in an in vitro system. Fresh and aged 125I-labelled human platelet-poor (PPP) and platelet-rich plasma (PRP) and whole blood clots were immersed in human plasma. Clot lysis was quantitated by measurement of released 125I. Fresh PPP clots were time- and concentration-dependently lysed by BM 06.022, alteplase, melanoma t-PA (mt-PA), and urokinase. Fifty per cent clot lysis at 4 h required 3.2-, 6.4- and 15.2-fold higher nM concentrations of mt-PA, BM 06.022, and urokinase respectively compared with alteplase. Maximal lysis (Emax) at 4 h was similar (84.1-87.6%) for BM 06.022, alteplase, and mt-PA, but lower (65.3 +/- 0.6%) for urokinase. Emax for BM 06.022 was lower (P < 0.05) than for alteplase for fresh and aged PRP and whole blood clot lysis. These data suggest that in vitro BM 06.022 achieved, compared with alteplase, the same maximal efficacy in fresh PPP-clot lysis despite a lower potency, but was less effective in lysing aged and fresh PRP and whole blood clots.

Rapid reversal of canine thromboembolic pulmonary hypertension by bolus injection of the novel recombinant plasminogen activator BM 06.022.

We used a canine model of embolic pulmonary hypertension induced by intravenous (i.v.) injection of autologous thrombi to evaluate whether the novel recombinant plasminogen activator (r-PA) BM 06.022 reversed pulmonary hypertension. The effects of BM 06.022 after bolus injection were compared with those of vehicle, alteplase, urokinase, and anistreplase in 6 dogs per group. Thirty minutes after initiation of treatment, the decrease in pulmonary artery pressure (PAP) caused by a bolus of 200 kU/kg (0.35 mg/kg) BM 06.022 was greater (p < 0.05) than that caused by a 2-h infusion of 1.33 mg/kg alteplase or of 40,000 U/kg urokinase and that caused by a bolus of 0.4 U/kg anistreplase but not that caused by a 15-min infusion of 1 mg/kg alteplase. At 3 h, all thrombolytic agents had reduced PAP equally. The greatest measured plasma concentration of BM 06.022 was higher (p < 0.05) than that of 2-h infused alteplase (4,498 +/- 716 vs. 519 +/- 119 IU/ml). We conclude that because of its bolus-pharmacokinetics, BM 06.022 more rapidly reversed thromboembolic pulmonary hypertension than did 2-h infusion of alteplase or urokinase or a bolus of anistreplase.

Influence of hepatic and renal failure on pharmacokinetic properties of the novel recombinant plasminogen activator BM 06.022 in rats.

BM 06.022 is a novel recombinant, unglycosylated plasminogen activator comprising only the kringle 2 and protease domains of human tissue-type plasminogen activator (t-PA), and it has a longer half-life than t-PA. Because t-PA is mainly cleared by the liver, rat models of hepatic and renal insufficiency were used to identify the main catabolic organ of BM 06.022, compared with alteplase (recombinant t-PA). Hepatic insufficiency in rats was chemically induced by pretreatment with carbon tetrachloride for 1 day; renal insufficiency was achieved by acute bilateral, surgical nephrectomy. Plasma concentration of functionally active BM 06.022 or alteplase was measured by an indirect spectrophotometric assay. Intravenous administration of 200 kU/kg of BM 06.022 or alteplase over 15 sec to rats with hepatic failure or olive oil pretreatment as control did not significantly alter the total plasma clearance (CL) of BM 06.022 vs. control (4.9 +/- 0.5 vs. 5.7 +/- 0.5 ml.min-1 x kg-1, NS) in contrast to alteplase (32.1 +/- 6.5 vs. 82.3 +/- 12.9 ml.min-1 x kg-1, p < 0.05). Renal insufficiency increased the CL of BM 06.022 vs. sham surgery (3.1 +/- 0.4 vs. 6.3 +/- 0.5 ml.min-1 x kg-1, p < 0.05) in contrast to alteplase (33.2 +/- 5.2 vs. 37.2 +/- 7.2 ml.min-1 x kg-1, NS). In vitro incubation of 2000 U/ml BM 06.022 or alteplase in citrate blood and plasma demonstrated a decrease of the plasma concentration with a shorter (p < 0.001) half-life for BM 06.022 than for alteplase in blood (71.9 +/- 3.1 vs. 130 +/- 3.3 min) and in plasma (62.9 +/- 1.2 vs. 129.9 +/- 5.3 min).(ABSTRACT TRUNCATED AT 250 WORDS)

Naftopidil, a new adrenoceptor blocking agent with Ca(2+)-antagonistic properties: interaction with adrenoceptors.

The interaction of naftopidil with adrenoceptors was studied in comparison to standard drugs. Naftopidil binds specifically to alpha 1-adrenoceptors. The Ki values are 58.3 nM for naftopidil, 0.43 nM for prazosin, and 197 nM for urapidil. The affinities of naftopidil to alpha 2- and beta-adrenoceptor sites are very low (> 6,000 and > 2,500 nM). Naftopidil relaxes aortic strips precontracted with norepinephrine concentration-dependently, and it shifts the concentration-response curve of norepinephrine in a parallel manner to the right. The pA2 values are 7.10 for naftopidil, 8.85 for prazosin, and 6.25 for urapidil. In pithed rats, naftopidil shifted the dose-response curve of methoxamine at equipotent hypotensive doses to the same extent to the right as does prazosin, but both drugs barely affected (in contrast to phentolamine) the response to norepinephrine. In concentrations that are about 10 times higher than those required for alpha 1-adrenoceptor blockade, naftopidil relaxes (in contrast to prazosin) aortic strips depolarized with K+, and it shifts Ca2+ concentration-response curves to the right (pA2 value of 5.90), thus suggesting Ca(2+)-channel-blocking activity. Both alpha-adrenoceptor and Ca(2+)-blocking activities are exerted to nearly the same extent by both stereoisomers. Naftipidil does not affect the response to isoprenaline-induced effects, indicating that the compound does not possess beta-blocking properties.

Hirudin and sulotroban improve coronary blood flow after reperfusion induced by the novel recombinant plasminogen activator BM 06.022 in a canine model of coronary artery thrombosis.

Thrombus formation in anesthetized, open-chest dogs was induced by electrical injury to the intimal surface of the left circumflex coronary artery. One-hour postocclusion, administration of vehicle to heparinized dogs (n = 12) did not induce reperfusion despite concomitant treatment with acetylsalicylic acid (ASA), sulotroban, or saline. Intravenous bolus injection of 140 kU/kg (= 0.24 mg/kg) of the unglycosylated t-PA variant BM 06.022 induced reperfusion in 4 out of 6 dogs, followed by flow deterioration. Pretreatment with i.v. ASA did not improve coronary blood flow (CBF). Conjunctive treatment with the thromboxane A2-receptor antagonist, sulotroban, (10 mg/kg i.v. bolus, followed by 10 mg/kg/h) or with recombinant hirudin, a specific thrombin inhibitor, (1 mg/kg/h) 30 min prior to i.v. injection of BM 06.022, prolonged (p < 0.01) the cumulative patency time (sum of time-intervals in which the coronary artery was patent) to 147.4 +/- 9.2 min in 4 out of 6 reperfused dogs and 129.9 +/- 12.3 min in 7 out of 8 dogs, respectively, compared to the saline plus BM 06.022 treatment (47.5 +/- 13.1 min) in 4 out of 6 dogs. The terminal CBF was higher (p < 0.01) after sulotroban plus BM 06.022 (7.0 +/- 1.7 ml/min) and hirudin plus BM 06.022 (6.3 +/- 1.5 ml/min) than after saline plus BM 06.022 (0.8 ml/min). These findings demonstrate that drugs with antithromboxane or antithrombin activity may improve CBF after reperfusion.

Pharmacokinetic and thrombolytic properties of unglycosylated recombinant tissue-type plasminogen activator (BM 06.021) produced in Escherichia coli.

Recombinant tissue-type plasminogen activator (rt-PA) was produced in Escherichia coli cells in order to obtain an unglycosylated rt-PA (BM 06.021) with increased thrombolytic potency due to altered pharmacokinetic properties. The pharmacokinetics were studied in rabbits upon intravenous infusion of 200 kU/kg over 30 min. The thrombolytic dose-response effects were evaluated in a rabbit model with 125I-labeled venous thrombi upon intravenous infusion over 4 h. The thrombolytic effects after intravenous bolus injection of 200 kU/kg BM 06.021 were investigated in a canine model of coronary artery thrombosis. All studies were performed comparing BM 06.021 with glycosylated rt-PA (alteplase). BM 06.021 demonstrated a longer (p less than 0.05) half-life (5.6 +/- 2.6 vs. 2.1 +/- 0.3 min) and a lower (p less than 0.05) clearance rate (7.5 +/- 0.8 vs. 22.2 +/- 3.1 ml.min-1.kg-1) than alteplase in rabbits upon intravenous infusion. The dose-response curve of BM 06.021 for thrombolysis in a rabbit model of jugular vein thrombosis was located to the left of that for alteplase with a 2.1-fold lower effective dose of 50% thrombolysis (ED50) of BM 06.021 (207 vs. 436 kU/kg). Intravenous bolus injection of 200 kU/kg BM 06.021 induced the same reperfusion rate (4/6) as intravenous infusion of 800 kU/kg alteplase over 90 min in a canine model of coronary artery thrombosis. The residual thrombus wet weight did not significantly differ between BM 06.021 and alteplase (5.7 +/- 1.8 vs. 6.3 +/- 1.1 mg). The results indicate that unglycosylated rt-PA (BM 06.021) has a higher in vivo thrombolytic potency than glycosylated rt-PA (alteplase).(ABSTRACT TRUNCATED AT 250 WORDS)

Double bolus administration of the novel recombinant plasminogen activator BM 06.022 improves coronary blood flow after reperfusion in a canine model of coronary thrombosis.

Reocclusion of coronary arteries is a major problem after successful thrombolysis in patients with acute myocardial infarction. We evaluated in a canine model of coronary thrombosis which is known to elicit reocclusion, whether an increased single i.v. bolus dose or two boli of the novel t-PA variant BM 06.022 improved coronary blood flow after reperfusion compared to i.v. injection of a standard single dose of BM 06.022. Double bolus administration, but not an increased single bolus dose of BM 06.022 significantly increased the maximum achieved coronary blood flow, prolonged the cumulative patency time, maintained blood flow at the end of the experiments, and reduced residual thrombus wet weight. Thus, double bolus administration improves coronary blood flow after reperfusion in the dog.

Evaluation of thrombolytic and systemic effects of the novel recombinant plasminogen activator BM 06.022 compared with alteplase, anistreplase, streptokinase and urokinase in a canine model of coronary artery thrombosis.

The thrombolytic and systemic effects of BM 06.022 were evaluated and compared with those of alteplase, anistreplase, streptokinase and urokinase in a canine model of coronary artery thrombosis. BM 06.022 consists of the kringle-2 and protease domains of human tissue plasminogen activator (t-PA) and is unglycosylated because of its expression in Escherichia coli cells. Thrombus formation in anesthetized open chest dogs was induced by electrical injury to the intimal surface of the left circumflex coronary artery at a high level site of obstruction. In heparinized dogs, none of six vehicle-treated animals exhibited reperfusion. Reperfusion was achieved in four of six dogs at 18.3 +/- 6 min after intravenous bolus injection of 140 kU/kg (0.24 mg/kg) of BM 06.022, whereas four of six dogs exhibited reperfusion later (p less than 0.05) at 76.5 +/- 16.1 min during infusion of 1.33 mg/kg of alteplase (0.13 mg/kg as initial bolus injection, followed by 0.66 mg/kg over 1 h and 0.53 mg/kg over 2 h). Significantly later (p less than 0.05) reperfusion than that achieved with BM 06.022 was achieved in five of six dogs at 57.8 +/- 12.1 min after intravenous injection of 0.4 U/kg of anistreplase. Streptokinase (21,000 IU/kg over 60 min) and urokinase (20,000 IU/kg as an intravenous bolus injection, followed by 20,000 IU/kg over 89 min) each induced reperfusion in three of six dogs but at 67 +/- 12 and 84.3 +/- 17.1 min (p less than 0.05 vs. BM 06.022), respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Pharmacological profile of beta-adrenoceptor blockers with vasodilating properties, especially carvedilol--rationale for clinical use.

The rationale for the combined use of beta-adrenoceptor antagonists and vasodilators is to improve the efficacy of the antihypertensive therapy and to reduce the incidence of side effects. If suitable coagents are selected and used at appropriate doses, the disadvantages of each separate component (compromised blood flow to individual organs, increase in total peripheral resistance, unfavorable lipid profile for beta-blockers; stimulation of counter-regulatory mechanisms, retention of water and electrolytes for vasodilators) can be balanced. In addition, the favorable effects of each (reduction in cardiovascular morbidity and mortality for beta-blockers, and favorable hemodynamic profile for vasodilators) may be used to advantage. Such a treatment rationale can be accomplished by a free combination or by using a dual-acting drug. From the practical point of view, the latter may be preferable. The basic requirement for such a drug is that the two effects are evoked in the same dose range. Carvedilol is a dual-acting drug designed to produce beta-blockade and vasodilation in the same dose range. The vasodilation is mediated predominantly by specific alpha 1-adrenoceptor blockade; at markedly higher concentrations additional vasodilating actions can be observed. These effects resemble those of Ca(2+)-antagonistic properties. However, they do not contribute to the acute blood-pressure-lowering activity, but may be responsible for the increased blood flow to some organs. At beta-blocking doses, carvedilol reduces the total peripheral resistance, and blood flow to the kidneys is preserved. Cardioprotection has been demonstrated in a variety of experimental investigations.

Vasodilatory action of carvedilol.

Carvedilol is a dual-acting drug designed to produce two complementary effects: beta-blockade and vasodilation. These effects are induced in the same dose range, a prerequisite for utilizing both properties in an appropriate manner. The vasodilation is mediated predominantly by specific alpha 1-adrenoceptor blockade. At markedly higher concentrations, additional vasodilating actions besides alpha 1-blockade can be observed. These effects resemble those of Ca(2+)-antagonistic properties. However, they do not contribute to the acute blood pressure-lowering activity of carvedilol but may be responsible for the increased blood flow to specific organs. At beta-blocking doses, carvedilol reduces the regional and systemic vascular resistance in various experimental models, healthy volunteers, and in patients with cardiovascular diseases such as hypertension, coronary artery disease, and heart failure. The profile of carvedilol thus insures beneficial treatment of hemodynamic disorders characterized by increased sympathetic tone and increased vascular resistance.

Coronary thrombolytic properties of a novel recombinant plasminogen activator (BM 06.022) in a canine model.

We studied the thrombolytic dose-response relationship of a recombinant plasminogen activator (rPA) (BM 06.022) compared with alteplase in a canine model of coronary artery thrombosis. BM 06.022 consists of the kringle 2 and protease domains of human tissue PA (tPA) and lacks oligosaccharide side chains because of its expression in Escherichia coli. Thrombus formation in anesthetized, open-chest dogs was induced by electrical injury to the intimal surface of the left circumflex coronary artery in the presence of a critical stenosis. Intravenous bolus injection of BM 06.022 (50, 100, 140, and 200 kU/kg) or of alteplase (200, 800, 1,130, and 1,600 kU/kg) 30 min after coronary occlusion to six heparinized dogs per group achieved a dose-dependent increase in reperfusion rate and decrease in residual thrombus wet weight. Vehicle-treated dogs did not reperfuse. Semilogarithmic regression analysis showed that the effective dose that produced 50% reperfusion of BM 06.022 (83 kU/kg) was 11.6-fold lower than that of alteplase (951 kU/kg). Comparison with infusion experiments showed that intravenous bolus injection of 140 kU/kg of BM 06.022 was equieffective to a 90-min infusion of 800 kU/kg (= 1 mg/kg) of alteplase as a standard treatment regarding reperfusion rate (66%) and time to reperfusion (15 +/- 6 vs. 18 +/- 8 min). Pharmacokinetic analysis for functionally active BM 06.022 or alteplase in plasma revealed a total plasma clearance of 4.1-6.6 ml/min/kg for BM 06.022 and of 12.6-42.3 ml/min/kg for alteplase.(ABSTRACT TRUNCATED AT 250 WORDS)

Thrombolysis with an Escherichia coli-produced recombinant plasminogen activator (BM 06.022) in the rabbit model of jugular vein thrombosis.

The recombinant plasminogen activator BM 06.022 consists of the kringle 2 and the protease domains of human t-PA and is unglycosylated because of the expression in Escherichia coli. The thrombolytic and pharmacokinetic properties as well as the hemostasis effects of BM 06.022 were investigated in the rabbit model of jugular vein thrombosis. The thrombi were 125I-fibrin labeled. Intravenous bolus injection of 50, 100, 200, and 400 kU/kg BM 06.022 or 400, 800, and 1600 kU/kg alteplase over 15 s to six rabbits/dose produced a dose-dependent increase of thrombolysis determined 2 h post injection. The dose-response curve of BM 06.022 was located left compared with that of alteplase. The effective dose of 50% thrombolysis (ED50) obtained by half-logarithmic regression analysis was 163 kU/kg (= 0.28 mg/kg) for BM 06.022 and 871 kU/kg (= 1.09 mg/kg) for alteplase. At equipotent doses (50% thrombolysis), the residual concentration of fibrinogen was 74.2% and 76.5%, that of plasminogen 66.7% and 69.4%, and that of alpha 2-antiplasmin 47.3% and 46% for BM 06.022 and alteplase, respectively. Pharmacokinetic analysis for plasma activity at a dose of 400 kU/kg revealed a half-life of 18.9 +/- 1.5 min for BM 06.022, whereas alteplase was distributed with a half-life of 2.1 +/- 0.1 min, accounting for 86.7 +/- 1.9% of the total AUC, followed by a beta-phase with a half-life of 13.8 +/- 0.9 min. Plasma clearance of BM 06.022 was 4.7 +/- 0.7 ml min-1 kg-1 compared with 20 +/- 1.2 ml min-1 kg-1 for alteplase.(ABSTRACT TRUNCATED AT 250 WORDS)

Pharmacokinetic properties of an Escherichia-coli-produced recombinant plasminogen activator (BM 06.022) in rabbits.

The recombinant plasminogen activator BM 06.022 consists of the kringle 2 and the protease domains of human t-PA and is unglycosylated because of its expression in Escherichia coli. The pharmacokinetic properties of BM 06.022 following intravenous injection over 1 min were characterized in anesthetized male New Zealand white rabbits. BM 06.022 was injected at doses of 50, 100, 200, and 400 kU/kg bw (n = 5-6/dose). Activity concentrations in plasma were determined using an indirect spectrophotometric assay. The maximum plasma concentration and the area under the plasma concentration vs. time curve (AUC0-00) of BM 06.022 increased linearly with dose. The systemic clearance ranged from 2.5 to 3.0 ml.min-1.kg-1 and did not show dose-dependency, in contrast to alteplase which was studied at doses of 200, 400, 800, and 1600 kU/kg. A direct comparison of clearance rates of BM 06.022 and alteplase at doses of 200 and 400 kU/kg each revealed a 8.5-fold slower clearance rate of BM 06.022. The majority (18/23) of rabbits with BM 06.022 injection showed a pharmacokinetic profile which was best characterized by a one-compartment model in contrast to alteplase (10/23). The dose-groups of BM 06.022 showed an average dominant half-life ranging from 11.6 to 15.4 min, which was about five-times longer than the dominant half-life values of alteplase (2.3 to 4.5 min). Assuming a two-compartment model in the remaining animals, the initial alpha-phase of BM 06.022 accounted for 40.1 +/- 13.2% (n = 5) of the total AUC, whereas the alpha-phase of alteplase accounted for 82.7 +/- 3% (n = 13) of the total AUC.