What are the interactions and side effects of proton pump inhibitors?
We have previously discussed the uses of and the mechanism of action of proton pump inhibitors. However, there are also a number of interactions and side effects tied to these PPI’s. In the case of omeprazole, it is metabolised via cytochrome P450 which can result in a prolonged elimination time for numerous other drugs such as warfarin, phenytoin and also diazepam. Also, when the patient is also on digoxin, it has been observed that there is a 10% increase in the digoxin bioavailability since there is a raise in pH. Also, when on ketoconazole or intraconazole there may be a decrease in its absorption. With regard to side effects, common effects seen are headaches, constipation and also diarrhoea. The patient may also suffer from gynaecomastia and also malaise however these are rare. Other rare side effects include impotence, photosensitivity and also bronchospasm. There may also be thrombocytopenia, muscle weakness and hallucinations.
Moreover, because there will be a reduction in gastric acid, it will make the patient more susceptible to infection from Campylobacter, C.difficile and also travellers’ diarrhoea. Interestingly, when the patient is withdrawn from PPI therapy, they will suffer from rebound acid hypersecretion, worsening the original problem when suffering from an ulcer.
A similar PPI is Lansoprazole which too has drug interactions. It has been found that when given to those on theophylline treatment, the plasma concentration of theophylline will be reduced therefore reducing expected clinical response. Also, it can increase the plasma level of tacrolimus by up to 81%. Moreover, it rifampicin and also St Johns Wort are given with Lansoprazole, it can result in a decreased in a fall in the plasma concentration of this PPI. It causes similar side effects to Omeprazole and can also cause rash, dizziness, and also intestinal nephritis as well as those mentioned above.