Process the following raw text block containing medical patient notes. Extract all instances of medications, dosages, and dates. Normalize the dates to ISO 8601 format (YYYY-MM-DD) and the dosages to standard metric units (mg, ml). Output the result strictly as a JSON object with keys: 'patient_id', 'medications' (array of objects with 'name', 'dosage', 'frequency'), and 'last_visit_date'. Omit any confidential identifiers not explicitly requested.