5. St John’s Wort and the contraceptive pill
St John’s Wort is a popular herbal remedy, used to treat the symptoms of mild depression. Some people assume that because it is a herbal remedy, it must be harmless. Quite the opposite.
St John’s Wort is an example of an enzyme inducer, a substance that speeds up the breakdown of another substance. By encouraging the breakdown of the other drug at a faster rate than normal, this means that the other drug becomes less effective.
While St John’s Wort can have this effect on many drugs, one of particular note is the contraceptive pill. St John’s Wort decreases the effectiveness of the pill, increasing the chance that the person taking the pill will become pregnant.
The interaction is so severe that the UK’s Medicines and Healthcare products Regulatory Agency has advised that the combination of St John’s Wort and the combined hormonal contraceptive pill should be avoided altogether.
6. Calcium supplements and other medications
As we get older, our bones become weaker, so many people are prescribed calcium and vitamin D supplements to strengthen their bones and prevent fractures. While these products benefit many, it is important to understand that they may affect how the body absorbs other drugs. These include drugs to prevent malaria, certain antibiotics and those used to treat an underactive thyroid.
For most drugs, this interaction can be overcome by leaving time between taking the calcium product and the other drug. A gap of between two and six hoursbetween taking calcium and other drugs is usually enough.
It is very important that if you are taking any of the drugs mentioned in this article that you do not stop taking any of them until you have consulted with your doctor. Any sudden changes to medication may have more severe consequences than any of the interactions listed in this article.