| Class | Vasopressor |
|---|---|
| Chemistry |
Phenylethylamine |
| Routes of administration |
IV, s/c, IM |
| Absorption |
Good oral bioavailability (enough for oral administration to be feasible) |
| Solubility |
pKa 8.79; excellent water solubility |
| Distribution |
VOD = 4L/kg; 45% protein bound. Distributes into catecholamine storage vesicles, where it persists for days. |
| Metabolism |
Not metabolised, it seems (not susceptible to COMT or MAO) |
| Elimination |
Eliminated slowly over hours/days. Distribution half-life is rapid(minutes). |
| Time course of action |
Effect lasts 20-60 minutes |
| Target receptor |
Directly acts on alpha-1 and beta-1 receptors, but this is not the main mechanism of effect |
| Mechanism of action |
By acting as a false neurotransmitter, metaraminol displaces noradrenaline from storage vesicles in noradrenergic synapses, therefore increasing the synaptic and systemic noradrenaline concenttration. Its main effects are therefore the same as the effects of noradrenaline. |
| Clinical effects |
Increased peripheral resistance, increased afterload, increased blood pressure; redistribution of blood flow from splanchnic circulation and skeletal muscle. Compensatory decrease in heart rate and cardiac output. |
| Literature reference |
PubChem |
| CICM details of understanding | Level 2 |
| Mentioned around Deranged Physiology | |
| Related SAQs |
Question 18 from the second paper of 2019 |