Potential therapeutic mechanisms of stable prostacyclin (PGI2)-mimetics in severe peripheral vascular disease.

In 2 randomized, double-blind studies, 109 diabetic patients with trophic lesions and 101 non-diabetics suffering from peripheral vascular disease (PVD) stage IV (Fontaine) received daily 6-hour i.v. infusions of iloprost (less than or equal to 2ng/kg/min) or of placebo over 28 days. Iloprost treatment was superior to placebo, showing ulcer healing in more than 60% of patients compared to less than 25% in the control group. The beneficial effects were sustained during a 1 year follow-up period. Platelet activation, adhesion, aggregation and release reaction on atherosclerotic lesions, impaired microvascular perfusion, loss of microvascular barrier function, increased white blood cell - vessel wall interaction and hemorheological disturbances are all believed to play a role in PVD. Stable PGI2-mimetics inhibit platelet activation by all endogenous mediators as well as platelet release of mitogenic factors (PDGF).

Clinical effects of intravenous iloprost in patients with intermittent claudication.

In a randomized patient-blind study iloprost or hydroxy-ethyl starch 200/0.5 were given i.v. 5 h daily for 2 weeks to 24 patients suffering from severe intermittent claudication due to peripheral vascular disease. An increase in pain-free walking distance of more than 50% occurred in 6 of 11 patients after the iloprost infusions and in 7 of 12 patients after HES treatment. No significant effects on haemodynamic or clinical chemistry tests were observed.

Pharmacokinetics and pharmacodynamics of radio-labeled iloprost in elderly volunteers.

The plasma levels and excretion of tritium-labeled iloprost in healthy elderly male and female volunteers have been measured after i.v. infusion of 2 ng X kg-1 X min-1 for 4 h and oral administration of 0.1 and 0.48 microgram/kg. During infusion, a steady-state of labeled compounds in the plasma was not achieved. Total radioactivity declined from a mean of 408 pg equiv/ml in three phases, with half-lives of 24 min, 1.7 h and 5.0 h, respectively. A steady-state of unchanged iloprost was reached rapidly with a peak of 81 pg/ml. Plasma levels declined biphasically with half-lives of 6 min and 31 min. Total clearance was 24 ml X min-1 X kg-1. Maximum concentrations of labeled substances after oral administration were 307 and 1,051 pg equiv/ml after 29 and 39 min, respectively. The peak of unchanged iloprost (116 pg/ml) was observed 7.5 min after an oral dose of 0.48 microgram/kg. Bioavailability was 16%. Iloprost was totally metabolized and the metabolites were mainly excreted in urine. The main biotransformation products in plasma and urine were tentatively identified by cochromatography as dinor- and tetranoriloprost and their glucuronides. ADP-induced platelet aggregation was reduced by 60% during the i.v. infusion and 15 min after oral administration of 0.48 microgram/kg. Heart rate and blood pressure were virtually unaffected. Common side-effects were facial flush, headache and nausea.

Pharmacokinetics and pharmacodynamics of the prostacyclin analogue iloprost in man.

Plasma levels of the prostacyclin analogue, iloprost, were measured by antibody/GC/MS in healthy male volunteers given 1 and 3 ng/kg per min i.v. for 45 min, and 1 microgram/kg p.o. Following i.v. infusion, the steady-state plasma levels of iloprost were strictly dose-dependent (46 +/- 8 pg/ml and 135 +/- 24 pg/ml). The disposition was biphasic with half-lives of 3-4 min and 0.5 h. After oral administration, absorption of the drug was extremely rapid, the maximum plasma level of 251 +/- 32 pg/ml being achieved after 10 +/- 6 min. The bioavailability was 16 +/- 4%. Platelet aggregation induced by 2 microM ADP was reduced by 53% and 68% at the end of the two different infusions, and by 68% 15 min after p.o. administration. The ex-vivo inhibition of platelet aggregation by iloprost was not affected by preceding drug treatment. The cAMP content of platelets was increased by a factor of 2.5 at the end of the infusions and to a lesser extent 15 min after oral dosing. A slight increase in heart rate occurred during the infusion and within 30 min after oral administration; blood pressure was virtually unaffected. Except for transient side-effects (facial flush and headache) no adverse reactions were observed.

[Treatment of Raynaud's phenomenon in scleroderma with a new stable prostacyclin derivative]. / Behandlung des Raynaud-Phänomens bei Sklerodermie-Patienten mit einem neuen stabilen Prostacyclin-Derivat.

In a single-blind trial 25 patients with progressive scleroderma and Raynaud's phenomenon intravenous infusions of iloprost, a prostacyclin derivative (carbaprostacyclin), were given daily for five hours during a six-day hospital stay, after a comparable initial single placebo infusion. Duration, frequency and intensity of Raynaud symptoms improved in more than 75% of the patients. This improvement was objectified by telethermometry which demonstrated acral hyperthermia and significantly briefer rewarming after standardized cooling of the hands. In addition, there was more rapid healing of ulcerations and necroses of the digital pulp. A significant inhibition of ADP- and collagen-dependent platelet aggregation was demonstrated during the iloprost infusion. Side effects, such as headache, nausea and tiredness occurred only transitorily during the infusion, were individually highly variable, and then only at higher concentrations. A dosage of 2 ng/kg X min was tolerated by all patients.

Pharmacological effects of iloprost (ZK 36 374), a stable prostacyclin analogue, in man.

Iloprost, a stable analogue of carbaprostacyclin, was infused for 72 h to 9 patients with advanced obliterative arterial disease. Total peripheral and pulmonary vascular resistances and blood pressure were decreased. Cardiac output was elevated with no marked extra cardiac load. The glomerular filtration rate was increased and tubular reabsorption of sodium and water reduced. Consequently, urine excretion increased. The renin-angiotensin system was not activated but excretion of renal kallikrein was augmented. Several patients showed clinical improvement. The drug was well tolerated except for gastrointestinal side-effects with the dose of 4 ng X kg-1 X min-1 or more.