Good for you for contacting the doc.
Unfortunately, doctors can't discuss their patients, even with family members, without permission from the patient. Because doctors are bound by doctor-patient confidentiality.
But the doctor can listen to your concerns, and pick up information from you.
If you know the herbs and treatments that your father is using, then you can tell the doctor. Then that information may help when he next sees your father.
It's very frustrating, but worth having another go.
Maybe tell the receptionist that you have information that the doctor needs to know.
Hope that helps.