Introduction
Hyoscine is a non-selective muscarinic acetylcholine receptor antagonist
that binds to a group of muscarinic receptors (M1-M5) that modulates the
release of acetylcholine or dopamine indirectly. M1-like muscarinic
receptors (M1, M3, M5) and M2-like muscarinic receptors (M2, M4)
activate and inhibit G-protein-mediated second messenger transduction,
respectively.1,2 Hyoscine blockade of the M2
muscarinic auto-receptor in the axon terminal is thought to raise
acetylcholine levels in the substantia nigra (SN) and ventral tegmental
area (VTA) midbrain areas, increasing striatal dopaminergic levels in
the mesopontine nuclei.3,4 Positive psychotic symptoms
like hyperactivity and stereotypy may result from such
activity.5,6 Inhibition of M4 subtype receptors, on
the other hand, has been linked to memory and attention
problems.1
We report a case of hyoscine-induced psychosis in a 9-year-old female.
The psychosis began when the medicine was taken and faded once it was
stopped. After a few days of being off the medicine, the child was
perfectly fine.