A complaint about a failure to counsel about potential for drug-drug interactions when supplying prescribed medication

In March 2022 the Professional Conduct Committee (PCC) completed an Inquiry into a complaint about the supply of an antibiotic, (clarithromycin 500MG) (‘Klacid® Forte’) to a 77- year-old female patient in circumstances where the patient was also taking warfarin.

The potential for interaction between clarithromycin and warfarin was not discussed between the pharmacist and the family members of the patient who collected the medication on behalf of the patient, and therefore, alternative therapies were not considered, nor was increased monitoring of the patient’s international normalised ratio (INR) put in place.

Following the supply and use of the antibiotic, the patient’s INR increased significantly, and she was admitted to hospital a week later. The patient had been experiencing a range of other serious health conditions, including chronic kidney disease, congestive heart failure, and she subsequently died in hospital.

There was no evidence at the Inquiry that the supply of medication and consumption thereof was the cause of death, or that the conduct of the pharmacist was responsible for the patient's death. Nonetheless, the Inquiry gave cause to identify a range of issues, mostly related to the need for extra care and counselling in relation to the supply of these medicines. In this case, whilst standard operating procedures within the pharmacy had highlighted the need for patient counselling “whenever possible”, on this occasion the prescription, although prepared by the pharmacist, was handed out by an assistant without any counselling being provided to the patient’s husband by the pharmacist.

The following issues were highlighted in particular:

i. the importance of offering counselling to patients or their representatives on the potential for drug-drug interactions between clarithromycin and warfarin;

ii. the necessity for the patient to be advised, if taking these medicines, to have increased frequency in monitoring of the INR when taking both clarithromycin and warfarin;

iii. the importance of consulting with the patient’s prescribing doctor prior to the dispensing of clarithromycin about:

a. the potential for drug-drug interactions between clarithromycin and warfarin

b. whether any better alternative antibiotic is appropriate

c. any action which should be taken if an interaction were to occur

d. the necessity for the patient to have the INR checked more frequently while taking both clarithromycin and warfarin

Important learnings

  • This complaint highlights the importance of effective counselling of patients by pharmacists in relation to the supply of medicines, particularly high-risk medicines with a high potential for interaction.
  • It also highlights the importance of proactive communication with prescribers to ensure that, if appropriate, an alternative medicine is prescribed, relative to the patient’s medical history and current health circumstances.
  • It further acts as a reminder of the importance of ensuring that all staff are aware of the importance of counselling patients and of knowing when to refer to the pharmacist as required. Relevant standard operating procedures (SOPs) should be reviewed to ensure there is sufficient clarity on the importance of counselling being offered to reduce the risk of a similar incident occurring in the future. Further guidance is available in the PSI Guidelines on the Counselling and Medicine Therapy Review in the Supply of Prescribed Medicinal Products from a Retail Pharmacy Business.
  • All Pharmacists should be reminded that they must counsel patients on their medicines, including the potential for a new drug to interact with existing medication, particularly for medicines which have a high risk of interaction, like warfarin. In accordance with the PSI Guidelines on the Counselling and Medicine Therapy Review in the Supply of Prescribed Medicinal Products from a Retail Pharmacy Business, the pharmacist should hand out all prescriptions where possible.
  • As stated in the PSI Guidelines on the Equipment Requirements of a Retail Pharmacy Business, all pharmacies:

“…must have a Drug Interaction Alert functionality as part of its computer dispensing system as well as an up to date hard copy and/or access to an online edition of an appropriate Interactions publication such as Stockley’s Drug Interactions (Ed. Stockley) (Pharmaceutical Press), Medscape Drug Interaction Checker (Online www. medscape.com). The interactions alert functionality should not be disabled during dispensing and the superintendent and supervising pharmacist must ensure the appropriate alert setting is activated.”

  • If the pharmacist has any reservations about potential interactions with the patient’s other medication, they should always contact the prescriber to discuss their concerns and discuss options for suitable, safer alternatives.
  • SOPs should highlight how the risk of therapeutic interactions with the patient’s existing medications are identified and managed in the appropriate manner as part of the dispensing process.
  • Warfarin is a ‘red flag’ medication with a significant potential for interaction with a range of other medicines. All staff within the pharmacy involved in the dispensing and supply of medicines should be aware that extra care is needed when warfarin is dispensed. Any time a new medication is prescribed alongside warfarin, there should be a check for any potential interactions. Pharmacists should check that a patient who is prescribed an additional medication when they are already taking warfarin has appropriate monitoring of their INR in place. They must also be counselled to be vigilant for signs of harmful side- effects that indicate their INR is not within the appropriate/targeted range.
  • Clarithromycin is a frequently prescribed antibiotic, that interacts with many commonly used medicines with a significant potential to cause patient harm. As it is also a high-risk medicine, extra vigilance and a thorough clinical review of the prescription as well as patient's medical history are needed when dispensing clarithromycin. The HSE PCRS have issued tips on safer use of clarithromycin.

Further reading to help you review your practice:

Advice on Standard Operating Procedure's (SOP's)