Sitaxentan (TBC11251, trade name Thelin) is a potent and selective Endothelin A receptor antagonist. Sitaxentan was under development by Encysive Pharmaceuticals (now Pfizer) for use in the treatment of pulmonary hypertension, congestive heart failure and asthma. It was launched in the major markets of the European Union (EU) under name Thelin for the treatment of pulmonary arterial hypertension. In December 2010, Pfizer discontinued clinical trials of sitaxentan worldwide and initiated voluntary product withdrawal from markets where it is approved due to life-threatening idiosyncratic risk of liver injury.

Clorprenaline is a β2-adrenergic receptor agonist. As a bronchodilator it has been used for the treatment of bronchial asthma, bronchitis and other respiratory diseases. It is a potential new lean meat-boosting feed additive because it can promote animal muscular mass growth and decrease fat accumulation.

A potent, selective and orally active receptor antagonist of leukotriene D4, verlukast (MK-571), was discovered and developed from a styrylquinoline lead structure based on a hypothetical model of the leukotriene D4 receptor. MK-571 blocks the action of LTD4 in animals and man, and is effective in a number of animal models of antigen-induced bronchoconstriction at plasma concentration at or below 2 ug/mL. MK-571 also blocks antigen-induced asthmatic responses in man. MK-571 is a potent and selective leukotriene D4 (LTD4) antagonist and ABCC multidrug resistance protein 1(MRP1) inhibitor. The cysteinyl leukotrienes (CysLTs), LTC4, LTD4, and LTE4, mediate their actions through two distinct G-protein coupled receptors. LTD4 is the preferred ligand for the CysLT1 receptor, whereas LTC4 and LTD4 bind with approximately equal affinity to the CysLT2 receptor. MK-571 is a selective, orally active CysLT1 receptor antagonist. It blocks the binding of LTD4, but not LTC4, to human and guinea pig lung membranes with Ki values of 0.22 nM and 2.1 nM, respectively. MK-571 effectively blocks LTD4 activation of recombinant human and mouse CysLT1 receptors but is ineffective at blocking LTC4 or LTD4 activation of the recombinant human or murine CysLT2 receptors.

The anticholinergic agent Flutropium is a classic competitive antagonist of acetylcholine. In in vitro experiments it is more effective than atropine. A poor enteral absorption is to be expected; this can be concluded from the low relative effectiveness after oral administration. After local administration as an aerosol it is superior to atropine with regard to both effectiveness and duration of action. It is used in Japan to treat asthma and chronic obstructive pulmonary disease. Flutropium can be described as a preparation which is free of side effects.

Vapiprost is a potent dicyclopentadiene thromboxane receptor antagonist that was being developed by Glaxo Wellcome in Japan. Vapiprost has been shown to be a potent and specific thromboxane (Tx)A2 receptor blocking drug in vitro using platelets and both vascular and airways smooth muscle preparations from different species. The drug is active in various experimental models of thrombosis. The potential clinical applications for a thromboxane receptor blocking drug include the treatment of thrombotic events and occlusive vascular disease. Phase III trials were underway in Japan for the treatment of deep vein thrombosis, which later were discontinued.

DIMEFLINE is a pneumokinetic and respiratory stimulant. It has been used for the treatment of respiratory insufficiency. The mechanism of action is unknown.

Hexoprenaline is a selective beta2-adrenoreceptor agonist indicated for use in the treatment of bronchospasm associated with obstructive airways diseases, including asthma, bronchitis and emphysema. In many countries the drug is used as tocolytic agent (under the trade name gynipral).

Oxitropium bromide (trade names Oxivent, Tersigan) is a bronchodilator indicated for asthma and chronic obstructive pulmonary disease. Oxitropium’s bronchodilation effect is similar to that of ipratropium bromide, but oxitropium is longer-lasting. The usual dose is 200 ug, 2–3 times daily. It blocks the muscarinic cholinergic receptors which mediate smooth muscle contraction in the airways. The manufacturer claims that regular use of oxitropium (200μg twice or three times daily) reduces the incidence of symptoms, including the need for night-time bronchodilators, and improves lung function in some patients; it is not intended for immediate symptom relief. Although widely used for many years (alone or in combination with short-acting beta agonists) for both maintenance treatment of stable disease and exacerbation of airway obstruction, Boehringer Ingelheim announced the discontinuation of Oxivent formulations at May 2004.

Acefylline is a stimulant drug of the xanthine chemical class. It acts as an adenosine receptor antagonist. Acephylline piperazine is a theophylline derivative with a direct bronchodilator action. It has the advantages over theophylline in being far less toxic and producing minimal gastric irritation. It is indicated for the treatment of asthma, emphysema, acute and chronic bronchitis associated with bronchospasm.Acefylline relaxes smooth muscles, relieves bronchospasm & has a stimulant effect on respiration. It stimulates the myocardium & central nervous system, decreases peripheral resistance & venous pressure & causes diuresis. The mechanism of action is still not clear, inhibition of phosphodiesterase with a resulting increase in intracellular cyclic AMP does occur, but not apparently at concentrations normally used for clinical effect. Other proposed mechanisms of action include adenosine receptor antagonism, prostaglandin antagonism & effects on intracellular calcium. Sodium phenobarbital is a non-selective central nervous system depressant that is primarily used as sedative-hypnotic.

Oxilofrine is a sympathomimetic used to treat hypotensive states, with cardiac stimulatory effects similar to those of ephedrine. It has never been approved for use in the USA as a prescription drug or as a dietary supplement. Oxilofrine has been found (1) to act predominantly as a beta1 agonist increasing the speed and force of heart muscle contraction (inotropic effects), specifically, increasing left ventricular ejection fraction and stroke volume; (2) to increase blood pressure; (3) to have variable effects on heart rate; and (4) to potentially increase oxygen uptake by the lungs.