| Class | Anorectic |
|---|---|
| Chemistry |
Indolalkylamine alkaloid, resembling reserpine |
| Routes of administration |
oral |
| Absorption |
Highly variable bioavailability, 7 to 87%, likely due to a individual polymorphism in first pass enzymes |
| Solubility |
pKa = 14.3, good water solubility; enough lipid solubility to cross the blood-brain barrier |
| Distribution |
VOD= 2.6L/kg, 97% protein-bound |
| Metabolism |
Rapidly metabolised by hepatic CYP450 enzymes to inactive hydroxylated metabolites |
| Elimination |
Minimal free drug is eliminated in the urine |
| Time course of action |
Half-life 0.5-2 hours |
| Target receptor |
Central alpha-2 receptors, where it acts as an antagonist |
| Mechanism of action |
By antagonising the presynaptic apha-2 receptors, yohimbine increases the synaptic release of noradrenaline and dopamine. This has an adrenaline-like effect peripherally, and an amphetamine-like effect centrally, including increased arousal and wakefulness (i.e. an opposite effect to drugs like clonidine and dexmedetomidine). |
| Clinical effects |
Increased alertness as well as nausea, vomiting, abdominal cramps, hypertension, tachycardia, exacerbation of motor tics, lower seizure threshold. Increased blood flow to muscle, regionally, as well as improved erectile function in males. |
| Literature reference |
Nasimudeen et al (2022) |
| CICM details of understanding | Not specifically listed in the CICM syllabus |
| Mentioned around Deranged Physiology | |
| Related SAQs |