You can only take action if the doctor deviated from the standard of care and you have been injured as a result. You have not mentioned any injuries that you have suffered and you would need another doctor to review the circumstances and be willing to testify that your doctor deviated from the standard of care.
You may want to consult a medical malpractice specialist, but I am not aware of any requirement that a medical doctor keep a patient. As for the prescriptions issue, call the doctors's office to clear up the misunderstanding, and start looking for a new doctor. That's much easier and more cost-effective than filing a lawsuit that may or may not have merit. Good luck.
This response is based on limited information. It is not meant as and does not constitute legal advice and does not create an attorney-client relationship.
Since you have not suffered any injuries yet even if the doctor departed from the standard of care there are no damages. Find a new doctor immediately or go to the emergency room.
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You should consult with another doctor for your continued care and treatment. If your doctor fell below the standard of care in your treatment and caused you damages, you should contact a medical malpractice lawyer.
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