Mifepristone is generally safe, but can cause complications if you have: 

• a heart condition
• asthma (but only if you are on long-term steroids)
• high blood pressure
• abnormal blood clotting
• kidney or liver disease
• an IUD in place (there is a greater risk of ectopic pregnancy)

The following medicines can block mifepristone, or cause other exacerbate existing health concerns: 

• corticosteroids (used for asthma and inflammatory treatments)
• St. John’s Wort (natural medication used to treat depression)
• Erythromycin, Rifampicin (antibiotics)
• Phenytoin, phenobarbital, carbamazepine (epilepsy treatments)
• Ketoconazole, Contractile (antifungal medications)

Do NOT take anti-inflammatory medications while taking mifepristone: 

• ibuprofen
• aspirin
• diclofenac

Also–strangely enough, do not drink grapefruit juice. It can prevent the mifepristone from blocking progesterone.