Side effects occurring during administration of epoprostenol (prostacyclin, PGI2), in man

Nanomedicine-mediated therapeutic approaches for pulmonary arterial hypertension

Nanomedicine has emerged as a field in which there are opportunities to improve the diagnosis, treatment and prevention of incurable diseases. Pulmonary arterial hypertension (PAH) is known as a severe and fatal disease affecting children and adults. Conventional treatments have not produced optimal effectiveness in treating this condition. Several reasons for this include drug instability, poor solubility of the drug and a shortened duration of pharmacological action. The present review focuses on new approaches for delivering anti-PAH drugs using nanotechnology with the aim of overcoming these shortcomings and increasing their efficacy. Solid-lipid nanoparticles, liposomes, metal-organic frameworks and polymeric nanoparticles have demonstrated advantages for the potential treatment of PAH, including increased drug bioavailability, drug solubility and accumulation in the lungs.

Treatment of pulmonary hypertension in patients with Hereditary Hemorrhagic Telangiectasia - A case series and systematic review

RATIONALE

Pulmonary Arterial Hypertension (PAH), a rare complication of HHT is associated with poor outcome. There are no trials to date that have investigated whether pulmonary vasodilator therapy improves hemodynamics or survival in this disease.

OBJECTIVE

To determine whether pulmonary vasodilator therapy improves survival, exercise capacity, or hemodynamics in HHT patients with pre-capillary PH.

METHODS

We performed a before-and-after observational study on a multicenter cohort of subjects with HHT-PAH who received intravenous prostanoid therapy. We then conducted a systematic review, searching Medline and EMBASE through December 2019. Studies that enrolled HHT-PAH subjects and reported treatment outcomes were selected. PROSPERO #158179.

RESULTS

Twenty-one articles were selected. Studies were before-and-after observational studies, case reports, and case series. Among all subjects with HHT-PAH, both mPAP (65 ± 19 pre-treatment vs 51 ± 16 mmHg post-treatment p = 0.04) and PVR (12 ± 6 pre-treatment vs 8 ± 4 WU post-treatment p = 0.01) improved with treatment. The mPAP improved with either oral (57 ± 17 pre-treatment versus 44 ± 13 mmHg post-treatment, p = 0.03) or intravenous (80 ± 15 pre-treatment versus 64 ± 16 mmHg post-treatment, p = 0.017) therapy. PVR also improved with either oral (10 ± 4 pre-treatment versus 6 ± 3 WU post-treatment, p = 0.004) or intravenous (17 ± 5 pre-treatment versus 10 ± 4 WU post-treatment, p = 0.04) therapy. Survival among HHT-PAH patients who received oral or intravenous therapy was not different (p = 0.2). Unadjusted survival among HHT-PAH patients was longer than that of IPAH patients (p = 0.008). There was no difference in side effects among HHT-PAH patient who received oral or intravenous therapy (p = 0.1).

CONCLUSION

Pulmonary vasodilator therapy is effective in improving hemodynamics of subjects with HHT-PAH and was not associated with increased risk of side effects.

International Union of Basic and Clinical Pharmacology. CIX. Differences and Similarities between Human and Rodent Prostaglandin E2 Receptors (EP1-4) and Prostacyclin Receptor (IP): Specific Roles in Pathophysiologic Conditions

Prostaglandins are derived from arachidonic acid metabolism through cyclooxygenase activities. Among prostaglandins (PGs), prostacyclin (PGI2) and PGE2 are strongly involved in the regulation of homeostasis and main physiologic functions. In addition, the synthesis of these two prostaglandins is significantly increased during inflammation. PGI2 and PGE2 exert their biologic actions by binding to their respective receptors, namely prostacyclin receptor (IP) and prostaglandin E2 receptor (EP) 1-4, which belong to the family of G-protein-coupled receptors. IP and EP1-4 receptors are widely distributed in the body and thus play various physiologic and pathophysiologic roles. In this review, we discuss the recent advances in studies using pharmacological approaches, genetically modified animals, and genome-wide association studies regarding the roles of IP and EP1-4 receptors in the immune, cardiovascular, nervous, gastrointestinal, respiratory, genitourinary, and musculoskeletal systems. In particular, we highlight similarities and differences between human and rodents in terms of the specific roles of IP and EP1-4 receptors and their downstream signaling pathways, functions, and activities for each biologic system. We also highlight the potential novel therapeutic benefit of targeting IP and EP1-4 receptors in several diseases based on the scientific advances, animal models, and human studies. SIGNIFICANCE STATEMENT: In this review, we present an update of the pathophysiologic role of the prostacyclin receptor, prostaglandin E2 receptor (EP) 1, EP2, EP3, and EP4 receptors when activated by the two main prostaglandins, namely prostacyclin and prostaglandin E2, produced during inflammatory conditions in human and rodents. In addition, this comparison of the published results in each tissue and/or pathology should facilitate the choice of the most appropriate model for the future studies.

Inhalation of repurposed drugs to treat pulmonary hypertension

Pulmonary arterial hypertension (PAH) is a rare, but severe and life-threatening disease characterized by vasoconstriction and remodeling of the pulmonary arterioles, leading to progressive increase in pulmonary vascular resistance and ultimately to right-heart failure. In the last two decades, significant progress in treatment of PAH has been made, with currently 12 drugs approved for targeted therapy. Among these, the stable prostacyclin analogues iloprost and treprostinil have been repurposed for inhalation. The paper highlights the development of the two drugs emphasizing the rationale and advantages of the inhalative approach. Despite substantial advances in the specific, mainly vasodilatory PAH therapy, disease progression is mostly inevitable and mortality remains unacceptably high. Thus, introduction of new drugs targeting the cancer-like remodeling of the diseased pulmonary arteries is urgently needed. Inhalation offers pulmonary selectivity and will hopefully pioneer the repurposing of novel highly potent drugs for effective aerosol therapy of PAH.

Specific Therapy in Severe Fetal Intrauterine Growth Retardation: Failure of Prostacyclin

Two case histories of severe, early onset intrauterine growth retardation are presented. Intravenous prostacyclin was administered in an attempt to promote fetal growth and thus prolong the pregnancy, but was unsuccessful and resulted in intrauterine death in each case. The possible reasons for the failure of this treatment and alternative therapeutic options are discussed.

Liposomal-delivery of phosphodiesterase 5 inhibitors augments UT-15C-stimulated ATP release from human erythrocytes

The use of liposomes to affect targeted delivery of pharmaceutical agents to specific sites may result in the reduction of side effects and an increase in drug efficacy. Since liposomes are delivered intravascularly, erythrocytes, which constitute almost half of the volume of blood, are ideal targets for liposomal drug delivery.

In vivo, erythrocytes serve not only in the role of oxygen transport but also as participants in the regulation of vascular diameter through the regulated release of the potent vasodilator, adenosine triphosphate (ATP). Unfortunately, erythrocytes of humans with pulmonary arterial hypertension (PAH) do not release ATP in response to the physiological stimulus of exposure to increases in mechanical deformation as would occur when these cells traverse the pulmonary circulation. This defect in erythrocyte physiology has been suggested to contribute to pulmonary hypertension in these individuals.

In contrast to deformation, both healthy human and PAH erythrocytes do release ATP in response to incubation with prostacyclin analogs via a well-characterized signaling pathway. Importantly, inhibitors of phosphodiesterase 5 (PDE5) have been shown to significantly increase prostacyclin analog-induced ATP release from human erythrocytes.

Here we investigate the hypothesis that targeted delivery of PDE5 inhibitors to human erythrocytes, using a liposomal delivery system, potentiates prostacyclin analog- induced ATP release. The findings are consistent with the hypothesis that directed delivery of this class of drugs to erythrocytes could be a new and important method to augment prostacyclin analog-induced ATP release from these cells. Such an approach could significantly limit side effects of both classes of drugs without compromising their therapeutic effectiveness in diseases such as PAH.

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PDE5 inhibitors can be successfully delivered to human erythrocytes via liposomes.

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This results in augmented PGI₂ analog-mediated ATP release.

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Liposomal binding to erythrocytes is rapid without affecting erythrocyte rheology.

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This is a novel method to augment PGI₂ analog-induced ATP release from erythrocytes.

A Case of Trapezium Avascular Necrosis Treated Conservatively

INTRODUCTION

Avascular necrosis (AVN) of the bones of the wrist most commonly involves the lunate followed by the proximal pole of the scaphoid and the capitate. Trapezium avascular necrosis is extremely rare with only two cases reported in the literature, both of which were treated surgically. In this article, we report a unique case of trapezium avascular necrosis treated conservatively.

CASE PRESENTATION

A 38-year-old man complaining of a 4-month history of mild pain on the base of his right thumb. MRI scan was performed. The clinical presentation and the imaging findings indicated avascular osteonecrosis of the trapezium. The patient was treated with immobilization of the wrist joint for a period of six weeks. Three months later, the patient was free of symptoms and the MRI scan revealed a normal trapezium.

CONCLUSION

AVN of trapezium is extremely rare. Our case shows that immobilization of an early stage avascular necrosis of the trapezium might be a treatment option.

Misoprostol modulates cytokine expression through a cAMP pathway: Potential therapeutic implication for liver disease

Dysregulated cytokine metabolism plays a critical role in the pathogenesis of many forms of liver disease, including alcoholic and non-alcoholic liver disease. In this study we examined the efficacy of Misoprostol in modulating LPS-inducible TNFα and IL-10 expression in healthy human subjects and evaluated molecular mechanisms for Misoprostol modulation of cytokines in vitro. Healthy subjects were given 14day courses of Misoprostol at doses of 100, 200, and 300μg four times a day, in random order. Baseline and LPS-inducible cytokine levels were examined ex vivo in whole blood at the beginning and the end of the study. Additionally, in vitro studies were performed using primary human PBMCs and the murine macrophage cell line, RAW 264.7, to investigate underlying mechanisms of misoprostol on cytokine production. Administration of Misoprostol reduced LPS inducible TNF production by 29%, while increasing IL-10 production by 79% in human subjects with no significant dose effect on ex vivo cytokine activity; In vitro, the effect of Misoprostol was largely mediated by increased cAMP levels and consequent changes in CRE and NFκB activity, which are critical for regulating IL-10 and TNF expression. Additionally, chromatin immunoprecipitation (ChIP) studies demonstrated that Misoprostol treatment led to changes in transcription factor and RNA Polymerase II binding, resulting in changes in mRNA levels. In summary, Misoprostol was effective at beneficially modulating TNF and IL-10 levels both in vivo and in vitro; these studies suggest a potential rationale for Misoprostol use in ALD, NASH and other liver diseases where inflammation plays an etiologic role.

Synergistic effects of prostacyclin analogs and phosphodiesterase inhibitors on cyclic adenosine 3',5' monophosphate accumulation and adenosine 3'5' triphosphate release from human erythrocytes

Prostacyclin (PGI2) and phosphodiesterase 5 (PDE5) inhibitors are potent vasodilators that are used alone and in combination for the treatment of pulmonary arterial hypertension (PAH). Although these vasodilators are known to stimulate relaxation of vascular smooth muscle directly, other cells in circulation, including erythrocytes, express prostacyclin receptor (IPR) and contain PDE5. The binding of PGI2 analogs to the erythrocyte IPR results in activation of a signaling pathway that increases cyclic adenosine 3',5' monophosphate (cAMP), a requirement for adenosine 3'5' triphosphate (ATP) release. Within this pathway, cAMP levels are regulated by phosphodiesterase 3 (PDE3), a PDE that is inhibited by cGMP, a cyclic nucleotide regulated by the activity of PDE5. Since inhibition of PDE3 enhances ATP release in response to PGI2 analogs, we investigated if the selective PDE5 inhibitors, zaprinast (ZAP) and tadalafil (TAD), would similarly increase cAMP and ATP release from human erythrocytes in response to the same stimulus. We determined that pretreatment of erythrocytes with one of two chemically dissimilar PDE5 inhibitors (ZAP or TAD, 10 µM) potentiated increases in cAMP and ATP release in response to incubation of human erythrocytes with the PGI2 analog, UT-15C (100 nM). These results suggest that a heretofore unrecognized synergism exists between IPR agonists and PDE5 inhibitors that could provide a new rationale for the co-administration of these agents as vasodilators in humans with PAH.

Asymptomatic Bradycardia Possibly Associated With Travoprost Therapy

Travoprost (Travatan®), a prostaglandin ophthalmic solution, is a second-line therapy for open-angle glaucoma, according to the Clinical Practice Guideline of the American Optometric Association. Recently, travoprost has been used as a first-line therapy in many patients because of its effectiveness and a once-daily dosing. It lowers the intraocular pressure by enhancing the aqueous humor outflow. Based on the product information, adverse effects such as ocular hyperemia, eye pain, pruritus, and bradycardia have been associated with travoprost therapy. Significant bradycardia is defined as heart rate or pulse of less than 60 beats per minute. We report on an 87-year-old man who experienced asymptomatic bradycardia while using travoprost ophthalmic solution. The pulse in our patient ranged from 42 to 50 beats per minute while receiving travoprost therapy during his hospitalization. Travoprost ophthalmic solution was discontinued because it was thought to be the likely cause of significant sinus bradycardia in our patient. After travoprost discontinuation, the average pulse of the patient was 66 beats per minute. Based on Naranjo’s Scoring System (an objective tool) for assessing the likelihood of drug-induced adverse effects, the score of 3 was obtained, which indicated a “possible” adverse effect. To our knowledge, this is the first case report about significant bradycardia possibly associated with travoprost therapy.

Safety and tolerability of bosentan in adults with Eisenmenger physiology

BACKGROUND

Bosentan, a dual-endothelin receptor antagonist, is an established treatment for pulmonary arterial hypertension. We hypothesized that bosentan is safe and well tolerated in patients with Eisenmenger physiology.

METHODS

In this pilot open-label study, we primarily examined safety and tolerability of oral bosentan. Patients were recruited from our adult congenital heart clinic following informed consent. Baseline and 3-month assessment included WHO functional class, resting oxygen saturations, 6-min walk test, transthoracic echocardiography and respiratory mass spectrometry. Patient clinical status and liver enzymes were closely monitored throughout.

RESULTS

All 10 study patients (42+/-4 years; eight female) tolerated bosentan well. No major adverse events or significant liver enzyme elevations were observed. All but one patient felt better; none felt worse. Four patients experienced transient leg oedema. Resting oxygen saturations (83+/-5 versus 80+/-5%; P=0.011) and the distance travelled in the 6-min walk test (348+/-112 versus 249+/-117 m; P=0.004) increased relative to baseline. Changes in echocardiographic parameters (maximum aortic forward flow velocity 1.3+/-0.1 versus 1.1+/-0.2 ms, P=0.013; pulmonary arterial acceleration time 66+/-10 versus 58+/-12 m/s, P=0.02) and pulmonary blood flow (3.45+/-1.2 versus 2.58+/-1.0 L/min, P=0.008) suggested improved pulmonary haemodynamics by study end. Other echocardiographic changes suggested improved right ventricular systolic function (septal amplitude 1.0 versus 1.1 cm, P=0.048; systolic tissue Doppler velocity 4.8 versus 2.3 cm s(-1), P=0.002) by study end.

CONCLUSIONS

Bosentan was safe and well tolerated in adults with Eisenmenger physiology both at initiation and after 3 months of oral therapy. Clinical status of patients and pulmonary haemodynamics appeared to improve, and this warrants further investigation.

Pharmacokinetics and Steady-State Bioequivalence of Treprostinil Sodium (Remodulin®) Administered by the Intravenous and Subcutaneous Route to Normal Volunteers

Treprostinil sodium is a chemically stable analogue of prostacyclin administered as a chronic, continuous subcutaneous infusion for the treatment of pulmonary arterial hypertension (PAH). There has been significant clinical interest in determining the feasibility of delivering treprostinil by intravenous infusion. Therefore, a bioequivalence and comparative pharmacokinetics study of the two routes of administration was conducted in normal volunteers. A randomized, two-period, crossover study design was employed. Each subject was dosed at 10 ng/kg/min for 72 hours by each route, with the infusions separated by a 4-day wash-out period. In the 51 subjects who received at least 24 hours of treprostinil administered subcutaneously and intravenously, the steady-state ratios of the geometric means (i.v./s.c.) and 90% confidence intervals for AUCss and Cmaxss were 92.9% (89.8-96.1%) and 106% (99.4-113%), respectively. Secondary pharmacokinetic assessments confirmed the comparability of the two routes of administration at steady state, and also demonstrated that the elimination half-life of treprostinil was 4.4 and 4.6 hours following intravenous and subcutaneous administration, respectively. Based on these findings it was concluded that intravenously and subcutaneously administered treprostinil are bioequivalent at steady state.

Eisenmenger's Syndrome

In general, most authors advocate nonintervention in Eisenmenger's syndrome, but an awareness of potential palliative measures to avoid destabilizing a delicately balanced physiology is needed as well. This approach has failed to alter long-term outcome, however. Survival for patients with Eisenmenger's syndrome has not improved substantially in the past several decades. Quality of life is universally altered by the presence of cyanosis, exercise intolerance, and the comorbid conditions associated with erythrocytosis. We therefore believe that the use of novel alternatives, as they become available, is warranted and that these alternatives are likely to be best evaluated in multicenter collaborative trials. The approach to the patient with pulmonary vascular obstructive disease (PVOD) should begin with maximization of palliative therapy and should, as compliance and teaching are ensured, proceed to the use of therapies designed to reverse the underlying proliferative changes in the pulmonary vasculature. Frequent checking of potential supplemental oxygen responsiveness and use of inhaled oxygen as needed to maximize systemic arterial saturation should be considered, although evidence of the value of home oxygen use is currently lacking. We favor systemic anticoagulation to a target international normalized ratio of 2.0 to 2.5. There are currently no published data supporting this practice in patients with PVOD, but we believe that as in patients with primary pulmonary hypertension, benefit is likely to outweigh risk. In the setting of a meticulous outpatient anticoagulation service, we have witnessed acceptably low bleeding event rates. A controlled clinical trial is warranted. Selective pulmonary vasodilators and antiproliferative agents hold significant promise in altering the natural history of PVOD associated with intracardiac shunting. The risk of paradoxic embolism and the theoretical worsening of right- to-left shunting compound the already high risk of systemically administered therapies; neither, to date, has been limiting in our patients. Studies of infused or newer subcutaneous and inhaled formulations are under way, and preliminary experience suggests real benefit--improved hemodynamics, improved exercise tolerance, and increased systemic arterial saturation--in this group of patients. Lung transplantation still trades a disease for another set of problems associated with long-term immunosuppression and chronic graft rejection in patients with previous sternotomy and thoracotomy and with a high acute surgical risk. Population studies of mortality and morbidity in patients with PVOD associated with congenital heart disease who receive transplants do not seem to suggest significant improvement with this therapy. In the future, the management of Eisenmenger's syndrome will probably include a multipharmacologic approach that targets several factors in the inflammatory cascade leading to vascular proliferation, perhaps offered in concert with novel surgical or transcatheter strategies designed to limit intracardiac shunting and, if desired, provide complete repair of intracardiac defects.

Attenuation of ischemic liver injury by prostaglandin E1 analogue, misoprostol, and prostaglandin I2 analogue, OP-41483

BACKGROUND

Prostaglandin has been reported to have protective effects against liver injury. Use of this agent in clinical settings, however, is limited because of drug-related side effects. This study investigated whether misoprostol, prostaglandin E1 analogue, and OP-41483, prostaglandin I2 analogue, which have fewer adverse effects with a longer half-life, attenuate ischemic liver damage.

STUDY DESIGN

Thirty beagle dogs underwent 2 hours of hepatic vascular exclusion using venovenous bypass. Misoprostol was administered intravenously for 30 minutes before ischemia and for 3 hours after reperfusion. OP-41483 was administered intraportally for 30 minutes before ischemia (2 microg/kg/min) and for 3 hours after reperfusion (0.5 microg/kg/min). Animals were divided into five groups: untreated control group (n=10); high-dose misoprostol (total 100 microg/kg) group (MP-H, n=5); middle-dose misoprostol (50 microg/kg) group (MP-M, n=5); low-dose misoprostol (25 microg/kg) group (MP-L, n=5); and OP-41483 group (OP, n=5). Animal survival, hepatic tissue blood flow (HTBF), liver function, and histology were analyzed.

RESULTS

Two-week animal survival rates were 30% in control, 60% in MP-H, 100% in MP-M, 80% in MP-L, and 100% in OP. The treatments with prostaglandin analogues improved HTBF, and attenuated liver enzyme release, adenine nucleotrides degradation, and histologic abnormalities. In contrast to the MP-H animals that exhibited unstable cardiovascular systems, the MP-M, MP-L, and OP animals experienced only transient hypotension.

CONCLUSIONS

These results indicate that misoprostol and OP-41483 prevent ischemic liver damage, although careful dose adjustment of misoprostol is required to obtain the best protection with minimal side effects.

Failure of epoprostenol (prostacyclin, PGI2) to inhibit platelet aggregation and to prevent restenosis after coronary angioplasty: results of a randomised placebo controlled trial

OBJECTIVE

To study the effect of epoprostenol (prostacyclin, PGI2) given before, during, and for 36 h after coronary angioplasty on restenosis at six months and to evaluate the transcardiac gradient of platelet aggregation before and after percutaneous transluminal coronary angioplasty (PTCA) in treated and placebo groups.

DESIGN

Double blind placebo controlled randomised study.

PATIENTS

135 patients with successful coronary angioplasty.

METHODS

Intravenous infusion of PGI2 (4 ng/kg/ml) or buffer was started before balloon angioplasty and continued for 36 hours. Platelet aggregation was measured in blood from the aorta and coronary sinus before and after PTCA in each group. Routine follow up was at six months with repeat angiography and there was quantitative assessment of all angiograms (those undertaken within the follow up period and at routine follow up). PRESENTATION OF RESULTS: Restenosis rates in treated and placebo groups determined according to the National Heart, Lung and Blood Institute definition IV. Comparison at follow up between the effect of treatment on mean absolute luminal diameter and mean absolute follow up diameter in the placebo group. Comparison of acute gain and late loss between groups.

RESULTS

Of 125 patients available for assessment 23 were re-admitted because of angina within the follow up period. Quantitative angiography showed restenosis in 15 (10 in the PGI2 group and five in the placebo group). Of 105 patients evaluated at six month angiography there was restenosis in nine more in the PGI2 group and 18 more in the placebo group. Total restenosis rates (for patients) were 29.2% for PGI2 and 38.3% for placebo (NS). The mean absolute gain in luminal diameter was 1.84 (0.76) mm in the PGI2 group and 1.58 (0.56) mm in the placebo group (p = 0.04); the late loss in the PGI2 group was also greater (0.65 (0.94) mm vs 0.62 (0.89) mm (NS) and there was no significant difference in final luminal diameter at follow up between the two groups (1.83 (0.88) mm v 1.59 (0.60) mm). The transcardiac gradient of quantitative platelet aggregation increased after PTCA in both groups, indicating that PGI2 in this dose did not affect angioplasty-induced platelet activation. Mean (SD) platelet activation indices in the PGI2 group were pre PTCA aorta 8.4 (4.1) v coronary sinus 8.8 (4.0) (p = 0.001) and post PTCA aorta 8.9(3.0) v coronary sinus 12.9 (5.7) (p = 0.001). In the placebo group the values were pre PTCA aorta 7.6 (3.3) v coronary sinus 7.4 (3.6) (p = 0.001) and post PTCA aorta 7.6(2.8) v coronary sinus 11.2(4.3) (p = 0.001).

CONCLUSION

The dose of PGI2 given was designed to limit side effects and as a short-term infusion did not significantly decrease the six month restenosis rate after PTCA. The sample size, which was determined by the original protocol and chosen because of the potency of the agent being tested, would have detected only a 50% reduction in restenosis rate. There was, however, no effect in the treated patients on the increased platelet aggregation seen in placebo group as a result of angioplasty. Angioplasty is a powerful stimulus to blood factor activation. Powerful agents that prevent local platelet adhesion and aggregation are likely to be required to reduce restenosis.

Comparison of the effects of adenosine and nifedipine in pulmonary hypertension

The hemodynamic effects of intravenously administered adenosine, a potent vasodilator, were examined in 15 patients with pulmonary hypertension. All patients were given adenosine, 50 micrograms/kg per min, increased by 50 micrograms/kg per min at 2 min intervals to a maximum of 500 micrograms/kg per min or until the development of untoward side effects. The patients were then given oral nifedipine, 20 mg every hour, until a greater than or equal to 20% decrease in pulmonary vascular resistance or systemic hypotension occurred. The administration of maximal doses of adenosine, 256 +/- 46 micrograms/kg per min, produced a 2.4% reduction in pulmonary artery pressure (p = NS), a 37% decrease in pulmonary vascular resistance (p less than 0.001) and a 57% increase in cardiac index (p less than 0.001). The administration of maximally effective doses of nifedipine (91 +/- 36 mg) produced a 15% reduction in the mean pulmonary artery pressure (p less than 0.05), a 24% decrease in pulmonary vascular resistance (p less than 0.01) and an 8% increase in cardiac index (p = NS). There was a significant correlation (r = 0.714, p = 0.01) between the reduction in pulmonary vascular resistance that resulted from adenosine administration and that achieved with the administration of nifedipine. Six patients had substantial reductions in pulmonary vascular resistance with adenosine but not with nifedipine. Thus, adenosine is an effective vasodilator in patients with pulmonary hypertension and can be used for safe and rapid assessment of vasodilator reserve in these patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Primate vascular responses to octimibate, a non-prostanoid agonist at the prostacyclin receptor

1. Octimibate is a potent inhibitor of human platelet aggregation, and appears to act (at least in part) through the prostacyclin receptor, as described in the preceding paper. Here, the vascular effects, both in vitro and in vivo, of octimibate have been compared to those of the stable prostacyclin (PGI2) mimetic, iloprost. Since octimibate shows extensive species variation and is potent at inhibiting platelet aggregation in primates, all of the experiments reported here have been carried out with primate tissue or in vivo in cynomolgus monkeys. 2. Activation of adenylyl cyclase in human lung membranes appears to involve stimulation of the vascular PGI2 receptor. Octimibate, as well as iloprost, stimulates adenylyl cyclase in this preparation. The EC50 values for iloprost and octimibate are 50 nM and 340 nM respectively. These values are similar to those seen with human platelet membranes. As with platelets, the maximal activation achievable with octimibate is 60% of that seen with iloprost. This result suggests that octimibate is a partial agonist for stimulation of adenylyl cyclase. 3. Iloprost (10-100 nM) relaxes human coronary and mesenteric artery precontracted with KCl, and also relaxes cynomolgus monkey aorta precontracted with phenylephrine. Octimibate appears to be a partial agonist for relaxation of human coronary artery precontracted with KCl; the intrinsic activity of octimibate (10 microM) is 0.15 compared to iloprost, and octimibate surmountably antagonizes the relaxant effects of iloprost with a Kp of 200 nM. Octimibate (up to 10 microM) evokes only weak relaxation of human mesenteric artery (precontracted with KCl) and cynomolgus monkey aorta (precontracted with phenylephrine). 4. The effects of iloprost and octimibate were compared in vivo in cynomolgus monkeys. In addition to inhibiting ex vivo platelet aggregation, both compounds cause hypotension with little effect on heart rate. The dose-response curves for inhibition of ex vivo platelet aggregation and a fall in mean arterial blood pressure were compared. The dose-separation (i.e., the relative differences in effective concentrations) for the two responses is similar with both iloprost and octimibate. 5. Since the pern; beral resistance vessels are intimately involved in regulation of systemic arterial blood pressure, the effects of both agents were tested on human peripheral resistance vessels (150-400pm diameter) in vitro. These vessels are relaxed by both iloprost and octimibate following precontraction with KCI. The IC50 value for iloprost is 44nM, and 1.7 microM octimibate evokes 50% of the maximal relaxation obtained with iloprost. Thus, the relative potencies of the two compounds in relaxing human subcutaneous resistance vessels are similar to their relative potencies in inhibiting platelet responses. This result correlates with the lack of platelet versus vascular selectivity seen with the in vivo monkey studies. 6. These results suggest that octimibate, a partial agonist at the prostacyclin receptor, is unable to discriminate between platelet and vascular prostacyclin receptors in primates.

The effect of ciprostene in patients with peripheral vascular disease (PVD) characterized by ischemic ulcers. The Ciprostene Study Group

This randomized, double-blind study investigated the effect of ciprostene, a stable epoprostenol (prostacyclin) analog in patients with peripheral vascular disease (PVD) characterized by ischemic ulcers. A total of 211 patients (106 ciprostene, 105 placebo) received IV infusions of ciprostene (120 ng/kg/min in 8-hour daily infusions for 7 days) or placebo. The two groups were comparable with regard to demographic data. Only 45% of the patients receiving ciprostene and 55% of the placebo patients completed the trial. The groups were similar in frequency of amputations, vascular surgery, and development of new ulcers. Among those who completed the trials an insignificantly higher percentage of patients receiving ciprostene had all ulcers heal completely. The reduction of ulcer size by at least 50% was higher in the ciprostene-treated group at month 4 (P = .005). Both ciprostene and placebo reduced the severity of a patient's rest pain. There was no difference in the ankle brachial index between the groups. Ciprostene induced a higher incidence of headache, nausea, and flushing during infusion when compared with the placebo group. The results confirmed inherent problems with studies in PVD, namely, scarcity of patients with ischemic ulcers, inclusion of severely ill patients leading to a high dropout rate, and a high placebo effect. Good tolerance and safety of ciprostene was documented in this patient population, and the therapeutic benefit was limited to partial reduction of ulcer size. Selection of patients with less advanced disease and a longer infusion of ciprostene may improve the clinical benefit of this agent.

Primary pulmonary hypertension: diagnosis, medical and surgical treatment

Primary pulmonary hypertension continues to present both diagnostic and therapeutic challenges to the physician, reflecting the lack of understanding about the basic mechanism of the disease. The natural history of the condition has been described only recently, and this has allowed a reasonably accurate prognosis for the individual patient to be determined. New treatments have been found effective, including heart-lung transplantation, which can now offer improved survival. Long-term intravenous infusion of prostacyclin has a place in the treatment of severely affected patients awaiting heart-lung transplantation. However, the major impact of prostacyclin has been, perhaps, to concentrate research upon the role of the endothelial cell in the development of this disorder, in particular the potential role of an impairment of release of the recently described endothelium-derived relaxing factor in certain forms of pulmonary hypertension. We have attempted in this review to focus on the problems of diagnosis and treatment together with current developments in the understanding of primary pulmonary hypertension.

Effect of short-term prostacyclin administration on restenosis after percutaneous transluminal coronary angioplasty

The effect of short-term prostacyclin (PGI2) administration on the incidence of restenosis after coronary angioplasty was studied in a prospective single-blind randomized trial of 286 patients. Of the 270 patients in whom dilation was successful, 134 received prostacyclin and 136 received placebo. Intracoronary prostacyclin was administered before and after dilation and then intravenously for 48 h. The control group received intracoronary placebo infusions before and after dilation. All patients received aspirin and dipyridamole before and after angioplasty, at least until follow-up angiography. Follow-up angiograms were obtained in 93% of patients in whom angioplasty was successful. Restenosis of one or more lesions was present in 34 patients (27%) who were given prostacyclin compared with 40 patients (32%) in the control group (p = NS). Acute vessel closure and ventricular tachyarrhythmias were more common in the control group than in the patients who received prostacyclin (acute vessel closure occurred in 14 [10.3%] of 136 versus 4 [3.0%] of 134, respectively, p less than 0.01; ventricular tachyarrhythmias occurred in 5 [3.4%] of 147 versus 0 of 139 respectively, p less than 0.05). Short-term administration of prostacyclin did not significantly lower the risk of restenosis after coronary angioplasty.

Ciprostene in patients with peripheral vascular disease (PVD). An open-label, tolerance trial

Epoprostenol (Prostacyclin) has been studied with various success in patients with peripheral vascular disease (PVD). We investigated the tolerance of a new, stable prostacyclin derivative ciprostene (9-beta-methyl carbacyclin) in 9 PVD patients. The drug was infused intravenously for 8 hours a day, once a week for 4 consecutive weeks, at a dose of 120 ng/kg/min. There were 6 men and 3 women with a mean age of 63 years (42-78). The PVD was verified by arteriography (9 patients) and by clinical findings. Patient #9 was lost to follow up after the first infusion and, consequently, was excluded from further evaluation. In patient #5 with a history of arrhythmias, the last ciprostene infusion had to be discontinued at 4.5 hours due to arrhythmias but his data were included into the evaluation. The cardiac disturbances were not judged to be ciprostene-related. Patients were followed monthly for 3 months after last infusion. Ciprostene was well tolerated although it produced adverse medical events (AMEs); most of them were rated as mild. The most frequent were those typical of prostacyclin: headache, facial flushing and warmth, body warmth, jaw pain and sleepiness. No consistent changes in blood pressure and heart rate were observed. One patient who initially had 9 ischemic ulcers underwent transmetatarsal amputation at month 4. The absolute and relative claudication time was measured by treadmill. As compared to baseline, the absolute claudication time increased significantly at week 2 and 4 of the infusion period and also at the end of month 3, but not at the end of month 4.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of a new prostacyclin analogue on anastomosis of ischemic colon in dogs

The effect of a new prostacyclin analogue OP-41483 on ischemic colonic anastomosis was investigated in dogs. Colonic ischemia was produced by devascularization of the marginal vessels in the left colon and graded into three degrees by measuring colonic blood flow with a hydrogen gas clearance method. The agent was administered intravenously after devascularization using a continuous infusion pump. The parameters studied were colonic blood flow in the submucosal layer, rate of anastomotic leakage, beta-glucuronidase activity and protein content of the colonic mucosa, and histologic changes. After administration of the agent, blood flow increased significantly and beta-glucuronidase activity at the anastomotic site was well preserved at a relatively high level in spite of ischemic change. The anastomotic leakage rate was significantly decreased. The present study proved that administration of this new prostacyclin analogue minimizes ischemic damage, and may be of considerable importance in ischemic colonic anastomoses.

Epoprostenol (prostacyclin) in unstable angina

The purpose of this randomized, double-blind multicenter trial was to investigate the potential therapeutic effect of epoprostenol (prostacyclin, PGI2) in patients with unstable angina, as compared with placebo, and to investigate the safety of this agent. Of the 184 patients enrolled, 28 did not fit the study criteria; of the remaining 156 patients, 30 received prostacyclin in an open-label fashion. In the double-blind portion of the study, 63 patients each received prostacyclin or placebo. The drug or its vehicle was infused intravenously up to 5 ng/kg/min dose for 72 hours with a tapering off period for the last 12 hours. Both treatment groups from the double-blind portion were comparable in regard to the demographic data, length of infusion, and total dose received. There were no significant differences between the placebo and prostacyclin group in the following clinical endpoints: levels of cardiac enzymes throughout hospitalization period (with the exception of lower SGOT level in the prostacyclin group at day 2), and severity of angina (throughout the study), and at the end of the study (day 30). The number of patients who had congestive heart failure, new myocardial infarction, balloon pump insertion, coronary artery bypass grafting, or percutaneous coronary angioplasty was similar in both groups. Similar results in regard to the efficacy endpoints were also apparent in the prostacyclin group that was treated under open-label fashion. There was also no difference in the New York Heart Association (NYHA) functional status at the end of the double-blind study.(ABSTRACT TRUNCATED AT 250 WORDS)

Hemodynamic effects of prostacyclin infusions in healthy volunteers

The selective hemodynamic effects of an intravenous infusion of prostacyclin on skin and on forearm blood flow during increasing doses up to 6 ng.kg.-1 min.-1 were evaluated in 12 healthy volunteers. The highest dose raised total skin blood flow (p = 0.0001) as measured by laser Doppler with a concomitant rise in finger skin temperature (p = 0.02). Capillary perfusion as measured by transcutaneous oxygen monitoring remained relatively unaffected (p = 0.25). Cold-induced vasoconstriction and the recovery thereafter were not influenced. Diastolic blood pressure tended to decrease (p = 0.06), but there was no change in systolic blood pressure, forearm blood flow, and calculated forearm vascular resistance. The authors conclude that prostacyclin may have dissimilar vasoactive potencies in different vascular beds as shown by a pronounced increase in total skin blood flow, owing to vasodilation of shunt vessels, simultaneously with an insignificant change in nutritional skin blood flow and forearm muscle blood flow.

Treatment of primary pulmonary hypertension intravenous epoprostenol (prostacyclin)

Ten patients with severe primary pulmonary hypertension and pronounced disability who were unresponsive to oral vasodilators were treated with intravenous epoprostenol (prostacyclin). All had been referred for heart and lung transplantation. Short term administration of epoprostenol (mean dose 5.5 ng/kg/min) increased the mean cardiac index from 1.8 to 2.2 1/min/m2, improved pulmonary artery oxygen saturation from 48% to 57%, and increased calculated tissue oxygen delivery from 10 to 11.8 ml/kg/min. The mean pulmonary vascular resistance fell by 18% while mean systemic artery pressure fell by 32%. Pulmonary artery pressure rose in only two patients. Continued intravenous infusion of epoprostenol for 1-25 months was associated with subjective and clinical improvement. Exercise tolerance improved as measured by an increase in the maximum rate of oxygen consumption during progressive exercise testing. In those six patients who were able to exercise before treatment it rose from a mean of 7 to 15 ml/kg/min. Those who had been unable to exercise before treatment achieved comparable rates of oxygen consumption after treatment. Two patients died on treatment, three have undergone heart-lung transplantation, and in five the treatment is continuing. Complications included episodes of septicaemia and ascites. In this uncontrolled study of patients with severe pulmonary hypertension epoprostenol seemed to offer a means of optimally dosing the patients with a vasodilator to reduce pulmonary vascular resistance and thus increasing cardiac output and oxygen tissue delivery. There was no evidence to suggest that this treatment influenced the progress of the disease.

Effect of prostacyclin (PGI2) on water and solute transport in the human jejunum

Prostacyclin is an arachidonic acid metabolite, synthesised throughout the gastrointestinal tract, which has different effects on water and electrolyte transport across a variety of mammalian gastrointestinal epithelia. Using a perfusion technique in the human jejunum of 11 healthy subjects in vivo, the effect of intravenous prostacyclin, 4 ng/kg/min, on jejunal water and solute transport from a glucose electrolyte solution was investigated. In the prostacyclin group (n = 5), prostacyclin was infused intravenously from 70-150 minutes, and buffer administered iv from 0-70 and 150-210 minutes. In the buffer group (n = 6), iv buffer was administered from 0-210 minutes. In the prostacyclin group, net jejunal absorption of water was inhibited from 90-120 min (p less than 0.05), 150-180 min (p less than 0.01) and 180-210 min (p less than 0.01), of sodium was inhibited from 90-120 min (p less than 0.05), 120-150 min (p less than 0.05), 150-180 min (p less than 0.01) and 180-210 min (p less than 0.01), and of chloride was inhibited from 90-120 min (p less than 0.05), 120-150 min (p less than 0.005), 150-180 min (p less than 0.01) and 180-210 min (p less than 0.01). Prostacyclin had no effect on net movement of glucose, potassium or bicarbonate. These results are consistent with a role for prostacyclin in the endogenous humoral regulation of water and electrolyte transport in the human jejunum.

Tolerance and pharmacology of ciprostene, a stable epoprostenol (prostacyclin) analogue in humans

Safety, tolerance, and pharmacology of 9-beta-methylcarbacyclin calcium (ciprostene calcium) was investigated in healthy male volunteers. This stable prostacyclin analogue was infused intravenously into groups of 12, 11, and three volunteers for three, six, and eight hours, respectively, in doses up to 480 ng/kg/min. Based on the tolerance data obtained, a single-blind, placebo-controlled study was conducted. Seven subjects were infused for 8 hr/d for three days with ciprostene at a maximum dose of 160 ng/kg/min and seven subjects received placebo. One subject from each group did not complete the infusion schedule, and they were not included in the final analysis. During infusion of ciprostene, consistent changes in blood pressure and heart rate did not occur. Most frequent adverse drug reactions consisted of headache, restlessness, nausea, perspiration, flushing, and jaw pain. As compared with placebo, ADP-induced platelet aggregation was inhibited during the infusion period (P = .048). Significant (P = .04) elevations of platelet cyclic AMP were observed in subjects during infusion of ciprostene. Pre- versus postinfusion routine laboratory evaluations, fibrinogen concentration, antiplasmin activity, and plasminogen and template bleeding times remained unchanged. Placebo- and drug-treated subjects had a daily postinfusion shortening of euglobulin clot lysis time (ECLT). The preinfusion minus postinfusion ECLT for ciprostene subjects on days 2 and 3 (133 and 118 min, respectively) compared with placebo (239 and 217 min) suggest a trend to increased fibrinolytic activity. Based on the outcome of this trial, it is estimated that ciprostene is about 15 times less potent than prostacyclin.(ABSTRACT TRUNCATED AT 250 WORDS)

The use of oxygen and prostacyclin as pulmonary vasodilators in congenital heart disease

We have obtained dose-response curves for the effects of prostacyclin on the pulmonary and systemic circulations of 10 patients with pulmonary hypertension secondary to congenital heart disease. With the subjects breathing air, prostacyclin caused statistically significant, pulmonary and systemic vasodilation. When the patients breathed 100% oxygen, pulmonary blood flow rose and pulmonary vascular resistance fell with no significant change in pulmonary artery pressure. Prostacyclin had a small additional vasodilator effect, but this did not reach statistical significance. Prostacyclin may be of some use in the assessment of the reversibility of an elevated pulmonary vascular resistance when surgery for the underlying congenital heart defect is being contemplated.

The cardiovascular and platelet actions of 9 beta-methyl carbacyclin (ciprostene), a chemically stable analogue of prostacyclin, in the dog and monkey

9 beta-Methyl carbacyclin (9 beta Me; ciprostene) is a synthetic, chemically stable analogue of prostacyclin (PGI2; epoprostenol). The platelet anti-aggregating and cardiovascular effects of 9 beta Me have been compared to PGI2 in anaesthetized monkeys and dogs. In addition, their haemodynamic effects have been compared in open-chest anaesthetized dogs and conscious dogs. Intravenous infusion of 9 beta Me and PGI2 to the anaesthetized monkey resulted in a dose-dependent hypotension, tachycardia and inhibition of ex vivo ADP-induced platelet aggregation. 9 beta Me was 72 times less active than PGI2 both as a hypotensive and anti-aggregating agent. Intravenous infusion of 9 beta Me and PGI2 to the anaesthetized beagle dog resulted in a qualitatively similar haemodynamic profile. Thus both substances induced a dose-dependent hypotension accompanied initially by a slightly increased heart rate, a dose-dependent increase in cardiac output, stroke volume and an increased peak LV dP/dt. At the higher doses studied, the initial increases in the parameters measured were succeeded by dose-dependent falls. 9 beta Me was 76 times less active than PGI2 as a hypotensive agent. In the anaesthetized greyhound, a dose-dependent anti-aggregating and hypotensive effect was seen with either drug, with 9 beta Me being 23 and 40 times less active than PGI2, respectively. Intravenous infusion of 9 beta Me and PGI2 to the conscious beagle dog induced a dose-dependent hypotension and a variable effect on heart rate. 9 beta Me was 33 times less active than PGI2 as an hypotensive agent. The duration of the hypotensive response induced by 9PMe was not significantly different from that induced by PGI2 in either monkey or beagle dog.

Prostacyclin and thromboxane in gynecology and obstetrics

The gynecologic and obstetric implications of the smooth muscle-relaxing, antiaggregatory prostacyclin and its endogenous antagonist, thromboxane A2, are reviewed. In addition to the vascular wall and circulating platelets, which are primary sources for prostacyclin and thromboxane A2, respectively, reproductive tissues produce great amounts of these prostanoids, evidently for the regulation of the vascular tone and/or vascular platelet interaction. Several gynecologic and obstetric disorders are characterized by abnormalities in prostacyclin and/or thromboxane A2. In primary menorrhagia the uterine release of prostacyclin is increased, and consequently menstrual blood loss can be reduced with various prostaglandin synthesis inhibitors. Prostacyclin relaxes the nonpregnant myometrium in vitro and may also do so in vivo, although intravenous infusion of prostacyclin has no effect upon the uterine contractility in nonpregnant or pregnant subjects. Patients with pelvic endometriosis may have increased levels of prostacyclin and thromboxane A2 metabolites in the peritoneal fluid. The prostacyclin/thromboxane A2 balance shifts to thromboxane A2 dominance in patients with gynecologic cancer. During pregnancy the production of prostacyclin and thromboxane A2 increases in the mother and fetoplacental tissue. Preeclampsia and other chronic placental insufficiency syndromes are accompanied by prostacyclin deficiency in the mother and in fetomaternal tissues and by an overproduction of thromboxane A2, at least in the placenta. These changes may account for the vasoconstriction and platelet hyperactivity, which are pathognomonic for hypertensive pregnancies. By directing the prostacyclin/thromboxane A2 balance to prostacyclin dominance (by dietary manipulation, administration of prostacyclin and/or its analogues, drugs with prostacyclin-stimulating and/or thromboxane A2-inhibiting action), it may be possible to prevent and/or treat hypertensive pregnancy complications in the future.

Side effects of prostacyclin in patients with angina pectoris and coronary artery disease

Although the exposure of human subjects to prostacyclin (PGI2) infusion has been broad, no systematic approaches have been made in order to investigate the dose-related side effects in patients with angina pectoris and coronary artery disease (CAD). We studied 25 patients with typical chest pain and overt CAD. All patients underwent a cycloergometer stress testing (25 W increments at 2-min intervals). PGI2 was infused in scalar doses up to 10 ng/kg/min. During the infusion 25 patients (100%) had facial flushing, 7 (28%) moderate headache and one (4%) had nausea. In addition, 4 patients experienced the typical chest pain and had significant (greater than or equal to 0.1 mV) ST segment depression at 8.10 ng/kg/min infusion rates. These patients had lower tolerance to exercise (6.7 +/- 1.7 vs. 8.8 +/- 1.9 min; p less than 0.05) and coronary artery lesions more severe than those observed in patients without drug-induced angina pectoris. Our data therefore indicate that PGI2 at therapeutic doses may induce myocardial ischemia in patients with angina pectoris, low tolerance to exercise and severe CAD. In patients with mild to moderate degree of CAD, PGI2 was found to be well tolerated. These findings suggest that patients with angina pectoris and low tolerance to exercise should be excluded from clinical studies directed at elucidating the effectiveness of PGI2 in cardiovascular disorders.

Effects of a stable prostaglandin analogue, L-644,122, in healthy and hypertensive men

L-644,122 is a chemically stable vasodilator prostaglandin analogue. It is a selective renal vasodilator in dogs. The object of the present study was to determine whether it increases effective renal plasma flow (ERPF) in man. L-644,122 was administered intravenously to 4 healthy volunteers and by mouth to 4 mild hypertensives. It did not increase ERPF. Instead it acted as a non-specific vasodilator, lowering diastolic blood pressure and increasing heart rate. An unexpected increase in glomerular filtration rate (19% greater than placebo) after low dose intravenous L-644,122 merits further study.

Effect of a hydantoin prostaglandin analogue, BW245C, during oral dosing in man

Following an open pilot study, the effects of repeated oral doses of BW245C, a hydantoin prostaglandin analogue, were studied in man. Six healthy volunteers received 150 micrograms BW245C or placebo 6-hourly for 5 days according to a double blind randomised balanced design with 7 days interval between treatments. Measurements of headache, facial flushing, heart rate, blood pressure, systolic time intervals, ECG, platelet aggregation responses to ADP and of subjective effects were made before and 1 and 3 h after the first dose of BW245C/placebo on days 1, 3 and 5 of dosing. BW245C produced significantly (p less than 0.05) higher headache scores than placebo on days 3 and 5; facial flushing, nasal stuffiness and abdominal discomfort were more frequent on BW245C than placebo. Heart rate, derived from the ECG, was significantly (p less than 0.05) higher and pre-ejection period significantly (p less than 0.05) shorter on BW245C at 1 h after dosing on each day. Left ventricular ejection time index, QS2 index, PR interval, QRS duration and T wave height were unchanged. Heart rate, counted at the radial pulse, and systolic and diastolic blood pressure, all measured lying and standing, were similar for BW245C and placebo. Platelet aggregation responses were not significantly different between the two treatments. The results indicate that repeated oral doses of BW245C, sufficient to cause moderately uncomfortable subjective effects, do not inhibit platelet aggregation.

Effects of intravenous infusions of prostaglandin D2 in man

Prostaglandin D2 (PGD2) was infused intravenously into normal male volunteers. Seven subjects received infusions of 16, 32, 64 ng/kg/min and six of these a further dose of 128 ng/kg/min. Each individual's maximum dose was limited by discomfort caused by intense facial flushing and nasal congestion. At these doses there was no significant effect on systolic or diastolic blood pressure nor on spirometric measurements. There was a small but statistically significant tachycardia at 64 and 128 ng/kg/min. Collagen- and adenosine diphosphate (ADP)-induced platelet aggregation ex vivo was not affected at any of the infusion rates. Infused PGD2 is unlikely to be a useful antithrombotic agent.

A chemically stable analogue, 9 beta-methyl carbacyclin, with similar effects to epoprostenol (prostacyclin, PGI2) in man

The effects of 9 beta-methyl carbacyclin, a chemically stable analogue of epoprostenol (prostacyclin, PGI2) were studied, in comparison with epoprostenol, both in vitro and in vivo in man. In vitro 9 beta-methyl carbacyclin and epoprostenol inhibited platelet aggregation induced by ADP, collagen, the endoperoxide analogue U46619 and arachidonic acid. The potency of 9 beta-methyl carbacyclin relative to epoprostenol was comparable in ADP and collagen-aggregated platelet rich plasma (PRP), 9 beta-methyl carbacyclin being 0.01 times as active as epoprostenol. The anti-aggregatory potencies of the two compounds were comparable in PRP and whole blood. The phosphodiesterase inhibitor isobutyl methyl xanthine enhanced the anti-aggregatory activity of both compounds in vitro. 9 beta-methyl carbacyclin and epoprostenol elevated platelet cyclic AMP, 9 beta-methyl carbacyclin being 0.04 times as active as epoprostenol. In a placebo controlled trial both drugs produces significant headache and facial flushing when compared with placebo. Nasal stuffiness, abdominal discomfort and nausea were reported on all three treatments. Both drugs caused significant and comparable increase in heart rate and decrease in pre-ejection (PEP) and PEP/left ventricular ejection time (LVET) ratio compared with placebo. Systolic and diastolic blood pressure, LVET and QS2 index were unchanged. Platelet aggregation responses to ADP were significantly inhibited by all three doses of both drugs compared with placebo. Bleeding time was significantly longer during epoprostenol infusion than either placebo or 9 beta-methyl carbacyclin infusion. Neither drug had significant effect, compared with placebo, on kaolin activated clotting time in PPP, PRP or in PRP in the presence of heparin, prothrombin time, partial thromboplastin time, thrombin clotting time, fibrinogen, fibrinogen degradation products or euglobulin clot lysis time. The pharmacodynamic effects and duration of action of 9 beta-methyl carbacyclin and of epoprostenol are similar; 9 beta-methyl carbacyclin is approximately 100 times less potent than epoprostenol in man.

Effects of single oral dose administration of a hydantoin prostaglandin analogue BW 245C in man

Following an open pilot study, BW 245C , a hydantoin prostaglandin analogue, was given by mouth in an aqueous solution to six healthy volunteers. The subjects received BW 245C 50 and 150 micrograms and placebo on separate occasions according to a double blind randomised design. Heart rate, blood pressure and, using visual analogue scales, facial flushing, abdominal discomfort and headache, were measured before dosing, at 15 minute intervals after dosing for 2 hours and at 30 minute intervals for a further 2 hours. Platelet aggregation responses to ADP and to collagen were measured before dosing and at 15 minutes, 45 minutes, 2 hours and 4 hours after dosing. Cutaneous bleeding time was measured before and 45 minutes after dosing. 150 micrograms BW 245C produced significant (p less than 0.05) facial flushing over the period from 15 to 120 minutes after dosing. Heart rate increased slightly but significantly (p less than 0.05) in response to both doses of 245C only at 75 minutes after dosing. Systolic and diastolic blood pressures were unchanged by either dose of BW 245C . Platelet aggregation responses to ADP were significantly (p less than 0.05) inhibited only at 120 minutes after 150 micrograms BW 245C . Aggregation responses to collagen were significantly (p less than 0.05) inhibited 45 and 120 minutes after 150 micrograms BW 245C and also at 120 minutes after 50 micrograms BW 245C . Bleeding time was unchanged in response to either dose of BW 245C . There was no change in headache or abdominal discomfort scores following either dose of BW 245C . Nausea was reported after 7 out of 12 administrations of BW245C but not after placebo. Nasal congestion was experienced by two subjects receiving 150 micrograms BW 245C and muscle tension and stiffness, especially of the jaw muscles, was also reported following administration of BW 245C but not of placebo. BW 245C is active when given by mouth and has similar pharmacodynamic effects to prostacyclin in man.

Effect of indomethacin on cerebral blood flow, carbon dioxide reactivity and the response to epoprostenol (prostacyclin) infusion in man

Cerebral blood flow (CBF) has been measured using a non-invasive Xenon133 clearance technique in six normal subjects after 2 days pretreatment with oral indomethacin at a dose of 100 mg/day. The results were compared with placebo given in a double blind balanced cross-over design. Indomethacin was found to result in a reduction in resting CBF of about 25% but the reactivity of the cerebrovascular circulation to carbon dioxide was preserved at normal levels. Infusions of epoprostenol (prostacyclin, PGI2) at a dose of 5 ng/kg/min resulted in a reduction of CBF of about 10% after placebo but no significant change in CBF after indomethacin. The results suggest that prostaglandins are involved in the maintenance of cerebrovascular tone but not in the mechanism of cerebral vasodilation accompanying hypercapnia. The combination of indomethacin and PGI2 has been proposed as a treatment of cerebral artery spasm and the findings suggest that the combination therapy would not be accompanied by undesirable intracerebral steal.

Positive inotropic effect of a stable analogue of PGI2 and of PGI2 on isolated guinea pig atria. Mechanism of action

Fluoroprostacyclin (10,10-difluoro-13,14-dehydroprostacyclin) a stable analogue of PGI2, induced an increase of contractile tension and a positive chronotropic effect on spontaneously beating guinea-pig atria. The increase in contractile tension was proportional to the dose (10(-8) to 2.5 X 10(-7) M) and never exceeded 40% of absolute initial controls. The chronotropic positive effect was low (12 +/- 4%) and not dose-dependent. The positive inotropic effect was also evident on electrically driven atria and was greater at the slower rates of stimulation. Atria from guinea pigs pretreated with reserpine were still sensitive to fluoroprostacyclin, although to a lower degree. The use of appropriate agonists and antagonists excluded the possibility that beta and alpha receptors are involved in the positive inotropic effect of fluoroprostacyclin. PGI2 showed the same behavior as fluoro-PGI2. Prostacyclins were able to reverse the decrease of contractility induced by verapamil, nifedipine, tetrodotoxin and xylocaine. But the reversal by PGI2 was no longer evident when the atrial contractility was completely abolished by the presence of these drugs in high concentrations. The inotropic effect of prostacyclins was more evident when Ca2+ was reduced in the medium. These results demonstrate that the cardiostimulant effect of prostacyclins is not simply adrenergic in origin. A direct effect on ion movements, mainly dependent on Ca2+ transmembranes fluxes, may be largely responsible for their positive inotropic effect.

The effects of continuous infusions of prostacyclin-Na (epoprostenol-sodium) on platelet counts, ADP-induced aggregation, and cyclic AMP levels in normal volunteers

Six male volunteers received either 0 (buffer), 2.5 or 5.0 ng/kg/min PGI2 X Na for 72 hrs. Various platelet parameters were monitored for an additional 72 hrs. Each morning, for seven consecutive days, and +1 and +6 hrs after the termination of the infusion, blood was drawn and platelet rich plasma (PRP) was prepared. The PRP was immediately exposed to 100 ng/ml PGI2 X Na, and the subsequent increase in platelet cyclic AMP was measured by radioimmunoassay. Aggregation in response to 2 or 4 microM ADP was measured simultaneously. Three volunteers returned for a second 72 hr infusion of 5.0 ng/kg/min PGI2 X Na. After 72 hrs, the infusion rate was gradually "tapered off" over a 12 hr period at which time the infusion was terminated. The sensitivity of the PRP to ADP-induced aggregation was recorded before, during, and after the "tapering off" regimen. Platelet counts were not altered by any of the infusions. The responsiveness of the platelet adenylate cyclase to exogenous PGI2 X Na was inversely related to the concentration of PGI2 X Na infused. Desensitization occurred and was more severe after 72 hrs of infusion than after either 24 or 48 hrs. For example, after 72 hrs at 5.0 ng/kg, platelets lost approximately 50% of their responsiveness to PGI2. ADP-induced aggregation was not significantly inhibited ex vivo by the infusion of 2.5 ng/kg/min PGI2. During the infusion of 5.0 ng/kg/min PGI2, ADP-induced aggregation was inhibited at 24 and 48 hrs, but by 72 hrs, the platelets began to respond to ADP more like control cells even though the PGI2 X Na infusion was continuing. When the infusion was abruptly terminated a hyperaggregable response (rebound) to exogenous ADP was observed. In subjects where the 5.0 ng/kg/min infusion was gradually "tapered off" over a 12 hr period, there was no evidence of platelet hyperaggregability at the time points studied.

Cardiovascular and platelet effects in man of BW 245C, a stable mimic of epoprostenol (PGI2)

1 BW 245C is a stable hydantoin prostaglandin analogue with a biological action similar to epoprostenol (PGI2). 2 Intravenous BW 245C (1,2 and 4 ng kg-1 min-1) produced a progressive increase in heart rate and pulse pressure in four healthy male volunteers. 3 These changes in heart rate and pulse pressure were accompanied by reduced ex vivo platelet aggregation to submaximal concentrations of ADP. 4 In man, BW 245C has a profile of action and potency similar to PGI2. However, it has a longer duration of action than PGI2.

Treatment of ischaemic stroke with prostacyclin

Ten patients with ischaemic stroke were treated with prostacyclin (2.5-5.0 ng/kg/min i.v. in 6 h courses 4-10 times during 1-2.5 days). In all patients a dramatic regression of hemiplegia, or hemiparesis, or aphasia occurred in the first few hours of prostacyclin infusion. Four to eight weeks later 6 patients left the clinic without neurological deficit; 3 patients had minor residual hemiparesis in upper limbs. In one patient, the occlusion of the contralateral carotid artery led to his death. It is considered that an antagonism may exist between endogenous cerebral prostanoids and prostacyclin and may have been responsible for the beneficial effects of prostacyclin therapy.

Effect of epoprostenol (prostacyclin, PGI2) on cerebral blood flow in man

Cerebral blood flow has been measured using the non-invasive Xenon133 clearance technique in eight normal subjects during an infusion of epoprostenol (prostacyclin, PGI2) at a dose of 5 ng/kg/min. The results were compared with a control infusion of saline given in a balanced order. PGI2 was found to result in a reduction in cerebral blood flow of about 8%. PGI2 also caused a small drop in diastolic blood pressure and it is proposed that the fall in cerebral blood flow may have been the result of disturbed autoregulation. The findings suggest that the therapeutic use of PGI2 in patients with cerebral artery spasm would not be accompanied by undesirable intracerebral steal.