Case study: Charcoal and drug interaction
Background information
A hospital pharmacist submitted a Yellow Card report after seeing a woman in her seventies who was taking several medications including:
For a chest infection
amoxicillin
clarithromycin
Commonly used to treat heart failure
candesartan
bisoprolol
furosemide
The patient was admitted to hospital with worsening heart failure symptoms and worsening atrial fibrillation whilst at the same time her chest infection had also not improved.
The pharmacist was concerned as the woman was taking charcoal with her other medication. Leading to the medicines being less effective. The pharmacist was also concerned that the warning stating ‘if on medication or if you have an unusual reaction to contact your doctor or pharmacist’ was not placed in a clear enough position on the container for patients to take notice of.
Investigation
A thorough review was conducted and there were no other similar reports on the Yellow Card scheme database. This safety issue was discussed within the specialist Self Medication Unit at the Medicines and Healthcare products Regulatory Agency (MHRA). It was concluded that charcoal did have the potential to reduce the absorption of other medicines, and that patients should seek advice from a pharmacist or doctor if any other medication is being taken when starting therapy with charcoal.
Response
A thorough review was conducted and there were no other similar reports on the Yellow Card scheme database. This safety issue was discussed within the specialist Self Medication Unit at the MHRA. It was concluded that charcoal did have the potential to reduce the absorption of other medicines, and that patients should seek advice from a pharmacist or doctor if any other medication is being taken when starting therapy with charcoal.
Result
Regulatory action was taken by the MHRA and the pharmaceutical company updated the product information to include a potential interaction between charcoal and other medicine products. The charcoal product’s packaging was updated to include a better design and clearer - warnings about its use with other medicines. This included advice to read the product information leaflet before use.
Additional information
Activated charcoal is an intestinal adsorbent which at lower dosages is used for the treatment of indigestion.
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