Are there any effective over-the-counter medications to stop diarrhea and vomiting associated with gastroenteritis?

Yes. Imodium (loperamide) a-d is available. Never use in children unless directed by your doctor (hardly any pediatrician will recommend). In older kids (over 12) and adults use cautiously only if diarrhea is watery, with no fever or abdominal pain and is causing dehydration (excessive loss of fluids) and you are not being able to drink enough back up.
Clear liquid diet. It is imortant to keep the infant hydrated and prevent dehydration if he is vomiting. Therefore clear liquid diet is preferred. If the mother is breastfeeding she should stop solid foods and continue breastfeeding frequently. There are no over the counter medication to cure vomiting and diarrhea.

Related Questions

How long does diarrhea and vomiting associated with gastroenteritis last?

It can be variable. The diarrhea can last up to 2 wks. The vomiting often lasts 2-3 days. Here is a little on vomiting for you http://www.Youtube.Com/watch?V=axhkggkon4q. Read more...
It depends on cause. Most viral gastroenteritis last an average of 3 days, some may last up to a week. The most important thing to consider is how well hydrated the child is, and if the child is able to keep fluids down. Be familiar with signs of dehydreation and consult your docor. Read more...

Aside from diarrhea and vomiting, what are the symptoms of gastroenteritis?

Dehydration. Apart from vomiting and diarrhea, the main concern in children with gastroenteritis is dehydration. Signs of dehydration include decreased urine production (you will notice this if you're changing less wet diapers than usual), dry lips, sunken fontanel in infants, dry skin, crying without tears, and decreased activity level. Read more...