Hello, my name is***** and I have over 20 years of experience as a veterinarian. I understand that you are concerned because Charlie ingested a 50mg Trazodone tablet.
Trazodone is used to control anxiety in dogs.
Trazodone is dosed at 1.7 to 9.5 mg/kg (0.8mgs to 4.3mgs per pound of body weight) orally every eight to 24 hours.
If Charlie is 30 pounds he is 13.6kgs (30lbs /2.2 lbs per kg = 13.6kgs), so he could take 10mgs to 58.6mgs and be within a normal dosing range.
50mgs of Trazodone is on the higher end of the dosing range, so side effects would be more likely. They could gastrointestinal effects (vomiting and diarrhea), sedation, incoordination, low blood pressure, excitement or agitation, and panting. Priapism (erection that lasts for an extended period of time) is an uncommon but possible side effect in people, so it is something to watch for in male dogs.
If Charlie is otherwise healthy and not taking any other medications then I would not be too worried, he may have an upset stomach, he may be very sleepy or uncoordinated, or seem hyper, but these effects should resolve over the next 24 hours or so.
Keep him quiet and confined so he doesn't hurt himself.
Please let me know if you have any further questions.