Interactions: Information sources

Last updated: Friday, July 08, 2016

Stockley’s Drug Interactions should normally appear fairly early on in your search strategy. This book tends to offer practical advice on patient management, but it does not cover all interactions.

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Check the SPCs for all the drugs involved as the information may differ between them. Some interactions are clearly flagged by manufacturers as contra-indicated, or there are well-established risks to the patient. However, some interactions may be listed in an SPC because they could occur in theory rather than being an actual problem in practice (such as those where cytochrome p450 is a minor part of a drug's elimination pathway). Use other sources to try and differentiate between these actual and theoretical concerns. We have a general learning module on using SPCs via the eMC here.

Always make sure that you check the Contra-indications, Special Precautions, Undesirable Effects, and Interactions sections of an SPC because relevant information may appear in any of these places. Do not rely on the Interactions section alone.

If you need to establish whether a drug is an inducer, inhibitor or substrate of cytochrome p450, then the Transformer website is very comprehensive. Alternatively the ‘Drug metabolism interactions’ chapter in the introductory section of Stockley’s is useful too.

Researching enquiries involving antiretroviral regimes can be complex because of the number of medicines involved. Fortunately HIV Drug Interactions.org makes this process much easier as you can enter all the antiretrovirals in question, together with the other medicine(s) of interest and it will cross-check them all for you. Another useful website describes interactions with medicines used to treat viral hepatitis - see Hep-Druginteractions.org

The subscription sources Martindale, AHFS Drug Information, Lexicomp or Micromedex (depending on what your department has access to), can be useful additional resources for interaction enquiries.

Embase and Medline may be helpful, usually towards the end of your search if you cannot find enough (or any) information. Most NHS sites access these databases via Athens. Your library or MI pharmacist can show you how to log in.

If your enquiry involves an alternative medicine, then you may need to refer to some of the sources listed in that tutorial to help you.

Be careful about conducting a general internet search on this subject. If you do, you may like to look at our brief guide to evaluating websites about medicines.

Presenting your answer 

Once you’ve asked sufficient questions, gathered the information required and assessed it, you’ll need to provide an answer. We can offer you some general guidance on answering clinical problems.