We have noticed quite a few posts querying the use of anti-histamines when talking Pitolisant/Wakix.
We have referred this to the manufacturer who have referred to the wording contained in the Summary of Product Characteristics (See e.g. here: https://www.medicines.org.uk/emc/glossary ) which you will find online or in each box of medicine within the Patient Information Leaflet.
Re. Anti-histamines, the exact wording from SPC:
'Anti-histamines (H1-receptor antagonists) crossing the haemato-encephalic barrier (e.g. pheniramine maleate, chlorpheniramine, diphenydramine, promethazine, mepyramine) may impair the efficacy of pitolisant.'
We believe this includes Piriton and similar generic forms, Phenergan so the older anti-histamines - this is because they cross the blood-brain barrier and have an opposing effect to Pitolisant/Wakix which enhances histamine in the brain causing wakefulness, rather than a sedative effect. So the effect of Wakix could be altered by this opposing effect.
Refer your pharmacist to the SPC wording & ask for a suitable product.
We believe sticking to the more recent brands of anti-histamine which do not cause drowsiness is the best option.