What can my 72 year old dad settle for pain and suffering caused internal bleeding due to wrong medication prescribed to him by his doctor?

There isn't any mathematical formula for determining compensation for pain and suffering. It just depends on the facts of the case. Compensation for pain and suffering is an amount in addition to the medical bills and is based on the medical reports which document the nature and extent of the injury.  Compensation for the medical bills is straight reimbursement.  I would ask for quadruple the medical bills to compensate for pain and suffering, but NOT expecting to get that.  The malpractice insurance carrier will respond with a lower offer as a starting point in negotiations.  Your dad can continue negotiating to try to get a larger amount from the insurance carrier.  If your dad is dissatisfied with settlement offers from the insurance carrier, he should reject the settlement offers and file a lawsuit for negligence against the doctor.  If the case is settled with the doctor's malpractice insurance carrier, NO lawsuit is filed.  If the case is NOT settled with the malpractice insurance carrier, your dad will need to file a lawsuit for negligence against the doctor prior to the expiration of the applicable statute of limitations or your dad will lose his rights forever in the matter.