WEANING FOR MEDICAL REASONS
If your doctor decides you need to take a drug (medicine) for a medical condition, make sure that they know how important it is for you to continue breastfeeding and check to see if a breastfeeding compatible drug can be used. You may not need to wean permanently, or at all. Do your own research, or get a second opinion from another doctor/hospital, if necessary.
Depending on the age of your breastfeeding child, and the frequency with which they breastfeed, certain drugs may have little or no effect on him.
If you must wean suddenly, it helps to express some milk from your breasts, for comfort, until you begin to produce less.
If you must be separated from your baby while undergoing treatment, but do not wish or need to wean, you can maintain your supply by expressing your milk.