If i was to administer a mineral oil enema, how much should i use?

I would: use the fleet brand of enema or the drug store version which is generally 6-8 ounces. Be sure to be lying down on your left side with feet elevated above hips and try to hold enema for 30 minutes or as long as you can. You can repeat if no results in 6 hours. IF that doesn't work you need an exam to be sure your problem is constipation and not something else