According to Walgreens, Seroquel and Seroquel XR come in the following dosages:

SEROQUEL 25MG TABLETSSEROQUEL 100MG TABLETSSEROQUEL 200MG TABLETSSEROQUEL 300MG TABLETSSEROQUEL 50MG TABLETSSEROQUEL 400MG TABLETSSEROQUEL XR 200MG TABLETSSEROQUEL XR 300MG TABLETSSEROQUEL XR 400MG TABLETS SEROQUEL XR 50MG TABLETSSEROQUEL XR 150MG TABLETS

So, yes, a 50 mg tablet is available. You could have (30) 100 mg tablets and (30) 50 mg tablets prescribed to make 150 mg daily. However, my experience has been that insurance companies will treat this as two separate prescriptions and charge you a copay for each. That may be why the pharmacy is giving you the 200 mg pills so that you end up taking 1 1/2 pills each day for a 150 mg dose.

It's okay to cut the regular Seroquel in half. You can't split the XR, though. That messes up the extended-release function of the pill. Pill splitters are available at any drugstore, and they cost less than $10. The pill splitters are so handy and take the guesswork out of trying to cut pills exactly in half.