Lighting, Light Fixtures, Ceiling and Exhaust Fans - 19lb vanity sconce from simple old work box?

I've searched, but can't find this anywhere, so apologies if it's been discussed.

We recently purchased a couple of three light vanity sconces to hang over the mirrors in the bathrooms as they lack any lighting aside from the ceiling fixture right now. They are quite heavy at about 19 pounds each. Can I install them into a regular old work box or will that just rip the drywall right out after I hang the sconces? If not, is my only option to cut up the drywall and patch after putting a ceiling fan type box in?

We have a fairly heavy two light sconse in our bathroom and it came with a jctn box adapter that has wings to directly fasten to the drywall on either side of the box.

Does yours perhaps have these?

I don't know about the wieght on a regular box. I can tell you that you don't need to cut up and patch drywall for a fan box. They make a setup that fits through the hole for the box and no patching is required.

The sconce didn't come with any type of box, but it sounds like it won't be a problem. I'll go to the store and check out the fan boxes. I was more concerned as to whether the drywall alone would be strong enough or if I was going to need to hit a stud.