A 70% reduction in
phenytoin absorption has been described when it is given with
enteral feeds (e.g. Isocal, Osmolite) administered via nasogastric tubes.
This interaction has been managed by giving the
phenytoin diluted in water 2 hours after stopping the feed, flushing with 60 mL of water, and waiting another 2 hours before restarting the feed. However, one study found this method unsuccessful. Other suggestions include waiting 6 hours after the
phenytoin dose before restarting the feed, stopping continuous feed 1 hour rather than 2 hours before and after
phenytoin administration, the use of twice daily
phenytoin or the use of
intravenous phenytoin. Monitor the outcome carefully. The same problem can also occur when
enteral feeds are given by the jejunostomy tube but methods to manage this are not yet established.