Weight gain from promethazine

[195fifi]

My neurologist has prescribed promethazine 50mg at night to help me sleep. I was wondering does it cause weight gain as other meds he put me on I gained 35lbs in 3 months and cannot lose the weight.Many thanks 195fifi

[marniecat]

Hi I had to stop taking phenergan as it made me hold a lot of excess fluid

[kaliska0]

There's a chance. It's actually one of the less likely options to cause such a problem. It's just a first generation antihistamine. I use hydroxyzine, which is the same class, as one of my sleep aids. Benadryl and Unisom are also first generation antihistamines with similar effects and promethazine was created while attempting to improve the effects of benadryl.

sciencehistory.org/historic...

The stronger psychiatric effects or increased potential side effects of antihistamines like hydroxyzine and promethazine compared to something like benadryl does make them too risky for people to randomly take without doctor supervision. Otherwise as far as sleep aids go they are on the lower end for health risks or side effects.

Promethazine has more impact on serotonin receptors than some other 1st gen antihistamines and serotonin altering meds have been known to cause weight gain in some people. While it's considered a weak to moderate impact on serotonin that would be my guess as to a potential cause for weight gain from that particular med. If the promethazine works you could ask about using a related med like hydroxyzine (atarax brand name usually) that might work equally well while potentially avoiding the weight gain.

It's also a sodium channel blocker that could cause you to retain fluids like the other poster but that's a lot of gain for just fluids and would probably have numerous other symptoms making you feel rather uncomfortable. Usually around 5lbs of weight gain, maybe 10, is the most you will see from "water weight" and by then you'll already be feeling bloated, stiff, possibly with swollen legs, feet, or hands and wanting to stop the med. A diuretic med that you can often find over the counter can solve that problem often without having to stop a useful medication but for 35lbs of weight gain without significant symptoms of fluid retention that's probably not the issue.

Pretty much every psychiatric med that could help sleep unfortunately has at least a mild risk of weight gain. Most also have a bunch of other potential side effects that range from annoying like dry mouth or mild dizziness to asking your doctor "why would you ever prescribe this to someone?!".