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Iloprost
General information
Iloprost is an analogue of prostacyclin (PGI 2 ), the pharmacodynamic properties of which it mimics, namely inhibition of platelet aggregation, vasodilatation, and cytoprotection. Iloprost has greater chemical stability than prostacyclin, which facilitates its clinical use [ ].
Iloprost is mainly used in patients with chronic critical leg ischemia due to atherosclerosis or Buerger’s disease. Episodic digital ischemia in patients with systemic sclerosis or related disorders is another use. The most frequently observed adverse reactions, facial flushing and headache, are caused by profound vasodilatation.
Most clinical experience with iloprost has been gained in patients with critical leg ischemia. An intermittent intravenous infusion of up to 2 nanograms/kg/minute for 2–4 weeks reduced rest pain and improved ulcer healing in roughly half of the patients with critical leg ischemia, including diabetics. Compared with placebo, the improvement obtained with iloprost was significant in most but not all individual clinical trials. In addition, a meta-analysis showed a 15% reduction in major amputation rate compared with placebo [ ].
Drug studies
Observational studies
The use of iloprost has been proposed in patients with systemic sclerosis, a disease that is often characterized by pulmonary hypertension and Raynaud’s phenomenon. Three patients with systemic sclerosis who were treated with iloprost developed acute thrombotic events [ ]. In one case, intestinal infarction occurred 1 day after infusion of iloprost. In another patient the left kidney was not perfused 22 days after the last infusion of iloprost because of thrombosis of the left renal artery. The last patient, 9 months after the start of treatment with iloprost, and 5 days after the last infusion, had an anterolateral myocardial infarction. The authors commented that their observations did not allow them to conclude that there is a direct relation between infusion of iloprost and thrombotic events. However, they said that this possibility should be considered, and they suggested that risk factors for thromboembolism should be carefully evaluated in each patient with systemic sclerosis who is receiving iloprost.
Inhalation of aerosolized iloprost is being tested in patients with severe primary or secondary pulmonary hypertension refractory to conventional therapy. The aim is to produce predominantly pulmonary vasodilatation without significant systemic effects. In an uncontrolled series of 19 patients, the most common adverse effects of inhaled iloprost were coughing, nausea, edema, and thoracic pain [ ]. In most patients, these effects were transient and rarely required a change in therapy.
Comparative studies
In a randomized, controlled study of cyclic iloprost or nifedipine in 46 patients with systemic sclerosis, the predictable adverse effects of iloprost (headache, nausea and vomiting, and diarrhea) were common but quickly resolved after the end of the infusion [ ]. They rarely required a temporary dose reduction. Hypotension occurred less often than with nifedipine.
The effects of PGE 1 and iloprost on microcirculation have been investigated in a randomized crossover study in 36 patients with peripheral arterial occlusive disease stage III and IV according to Fontaine [ ]. They received PGE 1 and iloprost by single 3-hour intravenous infusions on two different days at doses recommended by the manufacturers or as have been used in previous studies (PGE 1 : first hour 20 micrograms, next 2 hours 30 micrograms each; iloprost: first hour 0.5 ng/kg/minute, next 2 hours 1.0 ng/kg/minute). Adverse effects occurred in 19% (PGE 1 ) and 31% (iloprost). Dosage reduction was required in three patients receiving iloprost (hypotension, nausea, irritation of the infused vein), and in none in those receiving PGE 1 .
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