Taking cephalexin 500mg 3/day - tonsillitis & sulfameth/trimethoprim 800/160 2/day - uti. can i still take my adderall (dextroamphetamine and racemic amphetamine) xr 20mg 1/day? any interactions?

Yes: If you're taking your Adderall (dextroamphetamine and racemic amphetamine) for a well documented diagnosis such as adhd, then you definitely should continue it no matter what.

Drug interactions: You can use a drug interaction checker whenever you have questions about drug-drug interactions or drug - food interactions. Here is one option (Drugs.Com): https://www.drugs.com/drug_interactions.php Your pharmacist is also an excellent source of information.