Antacids: Neutralise gastric acid, aluminium containing antacids contribute aluminium to the diet and may cause constipation or lead to phosphorous deficiency. Longterm or inappropriate use can lead to Aluminium toxicity. Calcium containing antacids contribute calcium to diet and may cause constipation . Magnesium containing antacids contribute magnesium to diet and may cause diarrhoea. Longterm use may lead to magnesium toxicity.

Antiboitics: When amoxylin is given without regard to food nausea and diarrhoea are common side effects.It is better to take medicine with food to reduce nausea.

Clarithromycin: when taken it may cause taste alteration nausea and diarrhoea.

Metronidezol: May cause taste alterations and no alcohol should be used during treatment  if  alcohol is given and for 24 hrs afterwards alcohol can react with metronidezole and result in nausea , vomiting, headache, cramps .

Antisecretary agents:  Inhibit gastrophasis secretion . Citnitidine may increase formation of toxic metabollites. Nizartidine when taken with tomato based juices its potency is reduced.

Omeprazole and rebeprazole:  They inhibit secretion of acids may interfere with iron absorption. When iron supplements are necessary they should be given 2 hours before or after taking protonpump inhibitors.