Describe the physiological basis of the effects seen in the serotonin syndrome (80% marks). List the classes of drugs that may cause the serotonin syndrome (20% marks).
For a good answer candidates were expected to mention the role of serotonin (5
hydroxytryptamine) is an important neurotransmitter, a local hormone in the GIT and
involved in platelet reactions. It is formed from tryptophan and metabolised by MAO
(thus the potential effect of a combination SSRI with MAO inhibitor, or concurrent
use of several serotonin affecting drugs). Typically the serotonin syndrome is a
predictable effect of increased CNS levels of serotonin with a consequence of hyper
reflexia, tremor, clonus, skeletal muscle contraction and hyperthermia (but in
serotonin syndrome these effects are probably CNS mediated), hypertension, and
The expected list of drugs included the SSRI’s themselves, combination of SSRI’s
and MAOI’s, antidepressants (2nd generation [e.g Venlafaxine]) ,Tramadol (blocks
serotonin re-uptake), pethidine, fentanyl, ondansetron, sumatriptan (5-HT1 agonist).
References: Basic and Clinical Pharmacology, Katsung pg 264 – 269