In 2003, the U.S. Food and Drug Administration (FDA) staked out postal facilities in major cities across the country for a few days at a time and examined any parcels that appeared to contain drug products. They discovered prescription drugs mailed from all over the world. Later, they released a report detailing what they found: non-FDA-approved, foreign versions of U.S. drugs such as sildenafil, simvastatin, tamoxifen, warfarin, and carbamazepine; controlled substances such as codeine, diazepam, lorazepam, and clonazepam; drugs that require close physician monitoring, such as isotretinoin (which can cause birth defects), lithium (which poses a toxicity risk), and metformin (which requires kidney function monitoring); and foreign versions of 2 asthma medications that had been recalled in some countries because of faulty drug delivery systems. Some drugs arrived damaged, some were packaged in plastic bags or envelopes, while others lacked proper labeling or contained only foreign-language instructions. Most of the drugs came from Canada, but some of the products shipped from Canada came from other foreign suppliers.