Stopping Letrazole-washout period?

Does anyone know how long a time period or "washout "period is necessary to gauge whether much exacerbated rotator cuff pain is attributable to Letrazole? I had pretty painful rotator cuff problems prior to starting Letrazole ( and worse MSK pain in general after starting letrazole - though none of that pain was serious enough to make me consider stopping letrazole). But after having been on it 4 months, the rotator cuff problem became so painful it became unbearable. In fact it interfered with radiation treatment ( I am 2/3 of the way through) to the point where I could not tolerate holding my arms over my head for the radiation therapy appt without taking naproxen 500 mg which is raising my BP .... Any thoughts about how long to wait before trying another AI or Tamoxifen?
Thank you