Erlotinib hydrochloride and dasatinib should be taken together at the same time every day. The tablets must be swallowed whole and may not be broken. The tablets should be taken with 1 cup (about 8 ounces) of water. Dasatinib and erlotinib hydrochloride should be taken 1 hour before or 2 hours after meals or any other drugs, and should not be taken with grapefruit juice. The entire dose must be taken at 1 time. If you vomit within 30 minutes of swallowing the tablets, the dose may be replaced if the tablets can be seen and counted. If you are currently taking St. John's Wort, you should stopping taking if for at least 5 days before taking dasatinib.