Evidence for medicines

Understanding the use of evidence in medicine management

As with all prescribing, decisions to use medicines in palliative care should be based on the best available evidence for the effectiveness, appropriateness and safety of the proposed treatment. In some cases, the evidence supporting the use of medicines in palliative care can be difficult to find, and many important areas of research still remain.

For some medicines used in palliative care, the conditions approved by the Therapeutics Goods Administration (TGA) are more restrictive than the current level of evidence suggests. This is referred to as off-label use. Differences between the TGA approval and current evidence base may include the:

• Indication that the medicine is used
• Route of administration that the medicine can be administered, and
• Age or gender of the patient in which the medicine can be used.

To further establish this important evidence base requires investigating beyond 'usual practice' or 'expert recommendation' wherever possible.

Where to look for the evidence

CareSearch Finding Evidence pages provide wide ranging information and weblinks to help you understand the important issues when searching for the evidence, and to find the best evidence. Particularly useful pages include the Clinical Evidence pages.

The limitations of the evidence

Palliative medicine is an evolving field with a developing research culture. Many longstanding prescribing practices are empirical and local. The evidence base for these practices is often poorly established. Resources for research have been limited, and many of the research questions that need to be addressed are unlikely to attract funding from the pharmaceutical industry. Practical problems of recruitment, consent and infrastructure for research projects also hamper the development of the evidence base for palliative care prescribing.

What are the questions to ask in applying the evidence in patient care?

In using the literature on medicines in palliative care, it is necessary to analyse it carefully before attempting to apply it in practice, and this is known as 'critical appraisal'.

1. Is the study valid?
   Is the research question clear? Has the best methodology been used to answer that question? Is there any bias in the selection and allocation of patients within the study? Is the study blinded? Do all the numbers add up? Has there been good follow-up of all the participants in the study? How are the results analysed?
   
   
2. Are the results convincing?
   How were the outcomes measured? How were the results analysed? Does it all make sense? Does the discussion identify the weaknesses as well as the strengths of the study? Has it been published in a peer-reviewed journal (and therefore already been subjected to critical review)? Are there conflicts of interest for the authors? Do the conclusions match the actual findings of the study?
   
   
3. Is the study applicable to this particular clinical problem?
   Are those in the study comparable to the people the results will be applied to? For instance, does a study which looks at acute post-operative pain in otherwise well young people transfer to the care of older people with multiple comorbidities and chronic pain from cancer? Does the study directly look at the outcomes we are actually interested in? For instance, does a study which uses radiological changes in bone metastases as an outcome tell us about the effects of the study medication on bone pain? Does it also look at the harms and adverse outcomes associated with the treatment?

This approach to critical appraisal is used for quantitative intervention studies, and is the most appropriate type of study for answering questions about medications. Studies which are qualitative or which incorporate other methodologies may require different approaches to critical appraisal. However the overall three questions are the same.

For further information, see the CareSearch Appraising Evidence page.