Do we have legal recourse for a prescription mix up?

If your mother did not require medical treatment as a result of taking the wrong medication, she would not have any claim against the pharmaceutical chain.

If your mother required medical treatment as a result of taking the wrong medication, she could file a personal injury claim with the pharmaceutical chain's insurance carrier.  When your mother is released by the doctor after treatment for taking the wrong medication, she should obtain her medical bills, medical reports and documentation of any wage loss.  Her personal injury claim filed with the pharmaceutical chain's insurance carrier should include these items.  Compensation for the medical bills is straight reimbursement.  The medical reports will document the nature and extent of her injury and will be used to determine compensation for pain and suffering, which is an amount in addition to the medical bills.  Compensation for wage loss is straight reimbursement.  If the case is settled with the pharmaceutical chain's insurance carrier, NO lawsuit is filed.  If your mother is dissatisfied with settlement offers from the pharmaceutical chain's insurance carrier, she should reject the settlement offers and file a lawsuit for negligence against the pharmaceutical chain.  If the case is NOT settled with the pharmaceutical chain's insurance carrier, your mother will need to file her lawsuit for negligence against the pharmaceutical chain prior to the expiration of the applicable statute of limitations or she will lose her rights forever in the matter.