Working through the seven steps may therefore result in reducing or stopping medication that is no longer needed. This is referred to as ‘deprescribing’.  

The relative clinical effectivness of commonly used medicines can be compared using the number needed to treat (NNT). 

NNT can be used as one factor in assessing the effectiveness of a particular intervention. The NNT is the average number of people who require to be treated for one to benefit compared with a control in a clinical trial. It is expressed as the reciprocal of the absolute risk reduction. For example, if the NNT to prevent one death in five years is 25 people, then the annualised NNT will be 125 (25 x 5).

Although NNTs allow a numerical comparison between treatments, it is important they are not taken in isolation from other issues. For instance:

• What is the outcome being avoided? For example, death is clearly more significant than a vertebral fracture, but different outcomes will be more or less significant for individual patients 
• Over what period does the benefit accrue? Two drugs may have the same NNT to avoid one death, but a drug that achieves that outcome over six months is more effective than a drug that takes 10 years to achieve a positive effect. NNTs can be put on the same timescale by multiplying or dividing the figure appropriately, but this relies untested assumption that benefit accrues consistently over time 
• What is the likelihood and severity of harm caused by the drug? If a medicine saves the life of one patient in 25 but causes debilitating side-effects for the rest, then its costs may outweigh its benefits

Where do community pharmacists fit it? There are three main roles for community pharmacists in terms of addressing inappropriate polypharmacy:

• Providing post-medication review support for patients, including preventing inadvertent restarting of medicines
• Identifying patients at risk from polypharmacy at the outset
• Referring back to the GP for a prescribing review if necessary