Cyproheptadine (Periactin) is an antihistamine with appetite-stimulating properties. It can help increase appetite, leading to more frequent or larger meals and potential weight gain. However, like any medication, it has potential side effects such as drowsiness, dry mouth, dizziness, agitation, and abdominal pain. It's important to follow the recommended dosage and not exceed six months of use for appetite stimulation. While there are potential side effects, they are usually reversible and do not typically have long-term consequences. If you are considering taking cyproheptadine to help with weight gain, it's important to consult with a healthcare professional, such as a pharmacist or nutritionist, to discuss any potential risks or interactions with other medications you may be taking.