For drugs that require administration
on an empty stomachStop enteral feeding for 1-2 hrs before and after dosing if the tube is placed in the stomach Levothyroxine (Eltroxin),Rifampin (Rimactane)
Phenytoin (Epilog) and carbamazepine (Tegretol),Warfarin (Marevan),Floroquinolones ,Theophylline

Warfarin
Vitamin K directly blocks warfarin’s effects when given in doses of 140
to 500 mcg/day.Foods rich in Vit K : green tea, green vegetables (broccoli, spinach and lettuce), liver, lentils, peas, cauliflowerand cabbage)
Floroquinolones
Bind with divalent cations ( calcium and Magnesium )and should not
be given within 2 hours before or after them.

Drugs may affect GIT absorption of other medications
Sodium bicarbonate caps
May reduce absorption of ketoconazole,digoxin and iron.(space 2 hrs before and after).
Succralfate (Gastrofait)
May reduce absorption of phenytoin,digoxin,tetracyclines ,quinolones ,salicylate ,allopurinol and theophylline .(space 2 hrs).

reduce absorption of levothyroxine (Eltroxin) ,spacing is ineffective so we should use other agent for stress ulcer prophylaxis.
Antacids
(Al containing antacids) ex: Mucogel,Epicogel May reduce absorption of phenytoin,digoxin,tetracyclines ,quinolones ,iron,ACE inhibitors ,acetaminophen, NSAIDs ,allopurinol and theophylline .(space 2 hrs).

reduce absorption of levothyroxine (Eltroxin) ,spacing is ineffective so we should use other agent for stress ulcer prophylaxis.
Calcium containing antacids (Ca carbonate (calcimate))
Ca carbonate reduce assorption of tetracyclines , floroquinolones,phenytoin,iron,ACE inhibitors ,acetaminophen and levothyroxine (space 2 hrs).
sodium polystyrene sulfonate (sorbisteril):
separate dosing from other orally administered medicines by at least 3 hours. That time should be increased to 6 hours for patients with gastroparesis or other conditions resulting in delayed emptying of food from the stomach into the small intestine.
Osmolality
Many commercial liquids have
osmolalities well over 1000
mOsm/kg.. Diarrhea,
cramping, abdominal distention,
and vomiting may occur after
administration of hyperosmolar
products through the feeding
tube.

Aluminium hydroxide (Mucogel) syrup,Acyclovir syrup,Azithromycin (Zithromax) syrup,Carbamazepine (Tegretol) syrup,Dexamethasone syrup,Digoxin syrup,Diphenhydramine (Avil) syrup,Ibuprofen (Brufen) syrup, (Gaptin ) syrup.
Ferrous sulphate syrup.Fluconazole (Diflucan) syrup.Furosemide (Lasix) syrup.
Lactulose syrup.Leviteracetam (Tiratam) syrup.Metochlopramide (Prempran) syrup.
Potassium chloride syrup.Phenytoin (Epilog) syrup.Trimethoprime-sulphamethoxazole (Sutrim) syrup.

These effects may be
reduced by diluting medication
with by ratio1:5 or 1:10 of sterile water
before administration.
Inactive ingredients or excipients
in liquid products may also cause side effects when given enterally.
-Many sweeteners, including sorbitol,mannitol, lactose, saccharin,
and sucrose, may cause or worsen diarrhea in up to 50% of patients.
Syrups have sorbitol:
Tegretol (carbamazepine),Trimethoprime-sulfamethoxazole(sutrim),Ranitidine (Zantac),Valproic acid (Depakine),Domperidone(Motilium)