Benadryl & Dystonic Reactions (EPS)

[ResTech]

I have been wondering this for some time and tonight while bored at work, I decided to research it without much luck.... so hopefully someone can provide some information.

I had a call once for seizures and when we arrived it looked like a scene from the movie The Exorcist. The pt. was laying on the bed in an upstairs bedroom flailing about violently and uncontrollably. I have never seen anything like it before. It was obvious this was not seizure activity as the pt. was conscious and able to talk (more like cry and yell and express her fear and pain).

The pt. had a hx of schizophrenia and several other mental disorders and was being treated at a specialty hospital for her mental issues. Pt. had been placed on new meds (don't remember specific but where neuroleptics) for the schizophrenia within the past few days.

The PHRN on the medic unit arrived and suspected a dystonic reaction and called medical command who ordered diphenhydramine.... which did not work. The RN then administered Ativan which was successful in controlling the muscle reaction but never fully stopped it.

I know in many cases benadryl is indicated for treating extrapyramidal reactions and works successfully... what is its mechanism of action when used to treat EPS? And what doses are usually required?

Any info is appreciated. Thanks!

[FM291]

Benadryl has an anticholinergic effect, believe thats the reason for it with dystonic reactions without looking it up.

25 or 50 mg...works quickly.

[Mary Katherine Gallagher]

A dystonic reaction is both a dopaminergic and cholinergic type reaction. The last poster is correct in that Benadryl works because it is an anticholinergic. It works by restoring the excitatory-inhibitory balance in the brain's extrapyramidal motor system. You can also use Cogentin to treat dystonic reactions. There was a study that showed that versed was effective in treating acute dystonic reactions and actually worked faster than Benadryl. Ativan is in the same drug family as versed so I am thinking that is why the Ativan probably worked for that patient mentioned above. Drugs that can cause a dystonic reaction are various psych medications, reglan, phenergan, compazine etc.

On a personal note, after having had dystonic reactions on three different occasions, it is very very scary. The best thing you can do for your patient, other than getting command for Benadryl, is keep them calm with reassurance and an explanation of what is happening ot them.