Pulmonary Vasodilators

Property	Nitric Oxide	Iloprost	Sildenafil
Class	Inorganic gas	Synthetic eicosanoid with prostacyclin activity
Uses	ARDS, RVF, PHTN	PHTN	PHTN, erectile dysfunction
Presentation	Aluminium cylinders with 100/800ppm NO/N₂	Synthetic analogue of epoprostenol
Route of Administration	Inhaled	Inhaled	PO
Dosing	1-40ppm, via inspiratory limb of ventilator		20mg TDS
Absorption			40% PO bioavailability
Distribution	Avidly bound to Hb		95% protein bound, V_D of 100L
Metabolism	Metabolised to methaemoglobin and nitrite prior to reaching systemic circulation - t_1/2 of < 5s		Hepatic by CYP450
Elimination			Faecal
Mechanism of Action	Stimulates cGMP which reduces intracellular Ca²⁺	Stimulates cAMP which reduces intracellular Ca²⁺ and smooth muscle growth	Inhibits cGMP
Resp	Inhibits HPV, improves V/Q matching
CVS	↓ vascular resistance, ↓ PVR in ventilated alveoli and improving V/Q matching. ↑ Capillary permeability.	↓ BP with compensatory ↑ HR	↓ PVR
CNS	↑ CBF
Haeme	Inhibits platelet aggregation. MetHb	Inhibits platelet aggregation
Other	Rebound pulmonary HTN on abrupt cessation

References

Peck TE, Hill SA. Pharmacology for Anaesthesia and Intensive Care. 4th Ed. Cambridge University Press. 2014.
Smith S, Scarth E, Sasada M. Drugs in Anaesthesia and Intensive Care. 4th Ed. Oxford University Press. 2011.

Last updated 2020-11-10