I discourage the use of the Fleet type disposable enemas. They use a concentrated hypotonic chemical solution that causes water to be drawn out of your body into the lower colon to provide the volume of water for the enema.
Needless to say, this can be irritating to the lining of the colon as well as the sensitive external skin around the anus. These type enemas can also cause very uncomfortable cramping that last long after elimination has ended.
I recommend using plain water, or preferably a salt solution. It provides a far more effective and comfortable cleanse.