What yellow pill is SPO 500?

The yellow pill marked "SPO 500" is identified as Diphenhydramine Hydrochloride 25 mg, an over-the-counter antihistamine commonly used to relieve symptoms of allergy, hay fever, and the common cold. It can also be used as a nighttime sleep aid due to its sedative properties. Always consult a healthcare professional before use, especially if you have underlying health conditions or are taking other medications.