[Pharmacology of the pulmonary circulation]

Drugs with pharmacological activity limited to the pulmonary circulation are not at present available. Serotonin antagonists, specific thromboxane A2 inhibitors and prostacyclin may offer new possibilities for the treatment of certain forms of pulmonary arterial hypertension (PAH), but their clinical efficacy remains to be evaluated. Vasodilators simultaneously influence the pulmonary and systemic vascular resistances, and their overall hemodynamic effects in patients with PAH are therefore unpredictable. Therapeutic trials with such drugs should be closely monitored to avoid serious adverse reactions. Oral administration of beta-adrenergic agents, such as salbutamol or terbutaline, is preferable to digoxin in the treatment of patients with right ventricular failure due to chronic obstructive bronchitis. Right ventricular failure following massive pulmonary embolism may be aggravated by reduced blood flow through the right coronary artery. Increase of aortic perfusion pressure (e.g. noradrenaline) should be considered as a therapeutic measure in patients with arterial hypotension.