According to the search results, very few medications become toxic after their expiration date. However, it is important to note that expired medicine can become less effective over time and may not work as intended. Some medications that become toxic after expiration include:

• Tetracycline: This is an antibiotic that can cause serious kidney damage when expired.
• Nitroglycerin: This medication is used for heart conditions and has a short shelf life. Once it expires, it becomes less effective and can even be dangerous.
• Epinephrine (EpiPen): This medication is used for life-threatening allergic reactions and expires after one year. After the expiration date, the medication may no longer be effective in treating an allergic reaction and may even break down and become poisonous.

It is important to always check the expiration date before taking any medication and to dispose of expired medications properly. Expired medications can be disposed of in the regular trash if precautions are taken to ensure that children or pets cannot gain access to it. However, the best option is to participate in one of the periodic medication take-back events.