NPC Archive Item: ‘High risk’ prescribing in primary care – how prevalent is it?

NOTE – This is an archive post from the NPC and has not been updated since first publication. Therefore, some hyperlinks may no longer be working.
MeReC Rapid Review NPC Logo
11 July 2011
A cross sectional analysis of 315 general practices in Scotland found that 14% of the patients defined as particularly vulnerable to adverse drug events because of age, pre-existing disease, or co-prescription had received a ‘high risk’ prescription in the past year. ‘High risk’ prescribing included medicines such as NSAIDs, warfarin, methotrexate and antipsychotics in particular groups of patients. Considerable unexplained variation in the levels of high risk prescribing between practices was found. The patient characteristic most strongly associated with high risk prescribing was the number of long term drugs prescribed.
Level of evidence:
Level 3 (other evidence) according to the SORT criteria.
As discussed in the NPC’s recently published 10 Top tips for GPs, the risks associated with adverse drug events are particularly high in the following vulnerable groups of patients:
  • the old, particularly when frail
  • those with multiple serious morbidities
  • those taking several potentially hazardous medications
  • those with acute medical problems
  • those who are ambivalent about medication taking or have difficulty understanding or remembering to take medication
In these vulnerable groups, it is important to take particular care when first prescribing, to prioritise medication review, and to check purposefully for communication issues. Furthermore, it is important for clinicians to monitor patients and to ensure that essential laboratory tests are undertaken periodically; side-effects are detected; patients are given essential information and, where they want to be, are involved in decisions about their medicines; and that therapy is optimised.
What is the background to this?
Adverse drug events account for 6.5% of all hospital admissions, over half of which are judged to be preventable. The most commonly implicated drug classes are shown in Table 1. It is worth noting that just four classes of drug are associated with around half of preventable medication-related hospital admissions. These are antithrombotics (such as aspirin), anticoagulants, NSAIDs and diuretics. However, few data exist on how common high risk prescribing is in primary care or how it varies between patients and between practices.
The current study defined ‘high risk’ prescribing by identifying a set of 15 prescribing safety indicators (see Table 2 ) for which there was explicit guidance(from the BNF, CSM, MHRA, NPSA, SIGN) at the time of prescribing that that such prescribing carried significant risk of harm and should routinely be avoided. The indicators identified by this study generally encompass prescribing of NSAIDs, warfarin, methotrexate, and antipscychotics in particular groups of patients. These broadly fit into the drugs commonly associated with preventable harm that are identified in the NPC’s 10 Top tips for GPs (see Table 1). This cross sectional population database analysis examined the frequency of high risk prescribing in patients particularly vulnerable to adverse drug events, how reliably the indicators could distinguish between practices (which is critical if indicators are to be used to measure practices for high stakes evaluation, including performance management and clinical governance), and patient and practice characteristics associated with high risk prescribing.
Table 1. Drugs commonly associated with preventable harm in general practice
Source: NPC. 10 Top tips for GPs: Strategies for safer prescribing. 2011
What does this study claim?
19,308 of 139,404 (13.9%, 95%CI 13.7% to 14.0%) patients particularly vulnerable to adverse drug events had received at least one high risk prescription in the past year. After adjustment, the patient characteristic most strongly associated with high risk prescribing was the number of long term drugs prescribed (>11 vs. 0 long term prescribed drugs, OR 7.90, 95%CI 7.19 to 8.68). The study found that high risk prescribing also increased with age, rising from 6.7% in the under 40s to 15.9% in 70 to 79 year olds, but decreasing to 13.2% in those aged 80 and over age group (difference for age <40 vs. 70–79, 9.2%, 95%CI 8.3% to 10.1%). Other patient characteristics (e.g. rate of high risk prescribing in women vs. men) had smaller associations, although this was still statistically significant. After adjustment for patient characteristics, rates of high risk prescribing varied four-fold between practices, which was not explained by structural characteristics of the practices.
So what?
This study claims to be the first large-scale study of prescribing safety in primary care that uses multiple indicators based on explicit national prescribing safety advice, and examines how high risk prescribing varies between both patients and practices. However, there are many limitations to the study. For example, they could not distinguish between practices with generalised high risk prescribing and practices with individual prescribers who were higher than average risk. Further evidence of validity is needed to demonstrate that reducing high risk prescribing rates directly relates to reduced patient harm and fewer admissions to hospital due to medication-related adverse events. This study does however highlight the importance of strategies which may help improve the safety of prescribing in primary care, particularly in vulnerable patients e.g. regular medication review, good repeat prescribing systems, improved communication at hospital discharge.
The authors recognised that not all high risk prescribing may be inappropriate, and there are instances where clinicians may have to use their professional judgement to decide to use potentially high risk drugs. All prescribing decisions must balance risks and benefits, and in some patient circumstances a high risk drug may be appropriate for an individual, after an informed discussion with the patient. In such circumstances there should be close and regular monitoring and review of the use of high risk drugs in these patients.
Some high risk drugs are recommended for secondary care prescribing only. Medicines management services in primary care organisations need to monitor that clinicians in primary care are not inadvertently prescribing these for patients. Improving patient education and good communication between primary and secondary care should help further minimise the prevalence of high risk prescribing and help reduce the incidence of adverse drug events.
Although this study identified a four-fold variation in high risk prescribing between practices, none of the practice-level variables examined accounted for this variation. Further studies are required to understand the sources of variation between practices.
Cross sectional population database analysis.
315 Scottish general practices with 1.76 million registered patients; 139,404 (7.9%) were defined as particularly vulnerable to adverse drug events because of age (over 65 and over 75), co-morbidities, or co-prescription.
Intervention and comparison
How reliably each of 15 indicators — four each for non-steroidal anti-inflammatory drugs, co prescription with warfarin, and prescribing in heart failure, two for dose instructions for methotrexate, and one for antipsychotic prescribing in dementia; and a composite of all 15 could distinguish practices in terms of their rates of high risk prescribing; and characteristics of patients and practices associated with high risk prescribing in a multilevel model.
Outcomes and results
Table 2. Percentage of patients receiving high risk prescription
Prescribing safety indicator No. of patients receiving high risk prescription / No. of patients particularly vulnerable to adverse drug event

% (95% CI)
NSAID prescribed in patient with peptic ulcer disease without gastroprotection 4,371 / 49,574 8.8 (8.6 to 9.1)
NSAID prescribed in patients 75 and over without gastroprotection 4,464 / 8,840 50.5 (49.5 to 51.5)
NSAID prescribed in patients aged 65 and over prescribed angiotensin converting enzyme inhibitor or angiotensin receptor blocker and diuretic 3,908 / 44,492 8.8 (8.5 to 9.0)
NSAID prescribed in patients aged 65 and over with estimated glomerular filtration rate <60 2,272 / 27,668 8.2 (7.1 to 9.3)
NSAID prescribed to current warfarin user

550 / 16,182 3.4 (3.1 to 3.7)
Antiplatelet prescribed to current warfarin user 1,554 / 16,182 9.6 (9.2 to 10.1)
High risk antibiotic prescribed to current warfarin user 1,271 / 16,182 7.9 (6.4 to 9.3)
Oral azole antifungal prescribed to current warfarin user 116 / 16,182 0.7 (0.6 to 0.8)
NSAID prescribed to patient with heart failure

2,181 / 19,052 11.4 (11.0 to 11.9)
Tricyclic prescribed to patient with heart failure 1,246 / 19,052 6.5 (6.2 to 6.9)
Thiazolidinedione prescribed to patient with heart failure 278 / 19,052 1.5 (1.3 to 1.6)
Other “drugs to avoid” prescribed to patient with heart failure † 87 / 19,052 0.5 (0.4 to 0.6)
Methotrexate not prescribed with explicit instruction to take weekly 92 / 3,487 2.6 (2.1 to 3.2)
Methotrexate 2.5 mg and 10 mg co-prescription 410 / 3,487 11.8 (10.7 to 12.8)
Risperidone/olanzapine prescribed in over 65s with dementia but not psychosis 288 / 10,171 2.8 (2.5 to 3.2)
Patients with at least one high risk (all indicators) 19,308 / 139,404 13.9 (13.7 to 14.0)
† Other “drugs to avoid” are tadalafil, disulfiram, minoxidil, and class I and III antiarrhythmics, except amiodarone, verapamil, diltiazem, and itraconazole.
Source: Key results taken from table 2 of the full paper: Guthrie B, et al. BMJ 2011;342:d3514
NHS Quality Improvement Scotland, Scottish Government Chief Scientist Office.
Further information is available in the NPC’s 10 Top tips for GPs, guide to medication review and e-learning materials on evidence-informed decision making.
Further information on prescribing and safety information for individual drugs can be found on NHS Evidence.
Please comment on this rapid review in the NPC discussion rooms, or using our feedback form.
Make sure you are signed up to NPC Email updates — the free email alerting system that keeps you up to date with the NPC news and outputs relevant to you