| Class | Pulmonary vasodilator |
|---|---|
| Chemistry |
Pyrazinopyridoindole |
| Routes of administration |
Oral |
| Absorption |
Appears to have a high oral bioavailability |
| Solubility |
Acidic drug, pKa ~ 3.5 |
| Distribution |
very large VOD: 64 L/kg; highly protein bound (94%) |
| Metabolism |
Hepatic clearance is the main mode; metabolised by CYP 3A4 into a totally inactive metabolite |
| Elimination |
Half-life is 17.5 hrs |
| Time course of action |
Effects are maximal ~ 2 hours following oral administration |
| Target receptor |
Phosphodiesterase 5 |
| Mechanism of action |
Increases cyclic GMP by inhibiting phosphodiesterase 5, which is responsible for cGMP catabolism. Selective for vascular smooth muscle. |
| Clinical effects |
Pulmonary vasodilation, systemic vasodilation with hypotension, reflex tachycardia in reponse to this; priapism; headache |
| Literature reference |
TGA product information for Cialis, by Eli Lily |
| CICM details of understanding | Not specifically listed in the CICM syllabus |
| Mentioned around Deranged Physiology | |
| Related SAQs |