NHS Greater Glasgow & Clyde Area Drug and Therapeutics Committee
Greater Glasgow and Clyde Medicines
Medicines Update

Dual Antiplatelet Therapy (July 2014)

Clopidogrel or ticagrelor are indicated as part of a dual anti-platelet therapy (DAPT) regimen along with indefinite aspirin for management of patients with acute coronary syndrome (ACS) and / or undergoing percutaneous coronary intervention (PCI). The NHSGGC Guideline for Antiplatelet Therapy in Secondary Prevention of Coronary Heart Disease makes recommendations for DAPT duration in accordance with clinical circumstances.


Risks of inappropriate treatment

Concerns have been raised previously about the potential for patients to be continued on treatment after the anticipated stop date. Extended treatment means that patients continue to be exposed to the risk of adverse effects without additional clinical benefit.


Systems have been put in place to prevent inappropriate continuation of DAPT. These include the immediate discharge letter stating recommended duration of therapy, the patient and their GP being provided with an information leaflet and in the case of patients undergoing PCI at Golden Jubilee National Hospital (GJNH), a letter from the Prescribing Team advising the GP when DAPT should be stopped. Despite this, DAPT might not always be stopped at the correct time.


Auditing practice

Prescribing was audited in Glasgow North East during April and May 2014.

  • 43 practices were involved
  • 631 patients were reviewed; an average of 15 per practice.
  • 81% of patients had DAPT commenced on a cardiology ward or directly by GJNH.
  • General medical, medicine for the elderly and surgical wards were responsible for a small proportion of initiations.
  • The intended duration of therapy was generally readily identifiable.


The antiplatelet guideline published in May 2013 recommended that patients receiving a drug-eluting stent should generally be prescribed DAPT for 26 weeks. The audit identified that:

  • 26% of patients had therapy recommended for 26 weeks
  • Approximately one third of patients were recommended 12 weeks’ therapy
  • Another third were recommended a duration of 52 weeks (in line with previous advice).
  • 17 patients had 52 weeks therapy requested post-guideline launch (June 2013 onwards)
  • 4 patients had lifelong DAPT specified.
  • Reason for therapy duration deviating from the guideline was not always recorded.


70% of patients had emergency or elective PCI with the rest managed medically. Patients treated medically should receive 12 weeks of therapy; this correlates well with actual practice.


Almost 40% of patients (237) exceeded the intended duration; 77% of these were prescribed clopidogrel and 19% received ticagrelor.

  • A total of 7,537 weeks of excess therapy was prescribed
  • This averages 12 weeks per patient
    • range 1 – 504 weeks
  • The cost of excess treatment was £8,386. The cost of clopidogrel has reduced dramatically in recent years; if this pattern to continued, but with ticagrelor as the predominant agent, costs would have been in excess of £100,000.


Almost half of the patients undergoing PCI at GJNH had Prescribing Team correspondence recommending DAPT cessation in the patient record. A notable difference existed in the average excess duration between the groups who did receive a letter (20 weeks) and did not receive a letter (41 weeks). Just over half the patients received the correct duration of treatment and that was ireespective of whether the practice received a letter.


Changing practice following audit

A variety of actions and evaluations were undertaken as a direct result of the audit:


Practices are advised to review processes for managing advice on duration of DAPT therapy, eg by use of stop dates on the prescription.