What can I give 18 month old for constipation?

Constipation in Peds. For your 18 month old, you have a few options you can try. First you could try pedialyte, which can help with constipation. Also, you could try karo syrup, 5-6 drops in 1 ounce of of water, twice a day. And mylacon drops for gas. Good luck!
Start with juice. I like to start with adult concentrated apple or prune juice in amounts of 1-2 ounces once or twice a day as a natural solution.It takes a few days to work but can be repeated if needed. If that isn't helpful after a week or so, i like the otc MiraLAX (polyethylene glycol) product in quantities starting at a tablespoon full in liquid daily for as long as it takes.