Adverse drug reactions (ADRs) are a major cause of hospital admissions, financial burden, and increased morbidity and mortality. Studies looking at the issue of ADRs and hospital admissions highlight the preventable nature of many of these events. The World Health Organization defines an ADR as “any noxious, unintended or undesired effect of a drug that occurs at doses used in humans for prophylaxis, diagnosis or therapy”. Accordingly, ADRs can include allergic reactions and dose-related, predictable side effects of a drug. ADRs are a noteworthy reason for hospital admissions in the Western world, occurring at a rate of between 1% and 35% (Einarson, 1993; Lazarou et al., 1998). ADRs have also been noted to increase the length of hospital stay by an average of nearly two days which is a significant financial expense for the healthcare system. A study by Bennett et al. (2007) demonstrated that the mean cost per hospital admission for febrile neutropenia was $13,372.

Several factors can affect the likelihood of an ADR occurring. These include the length of treatment, polypharmacy, non-adherence, seriousness of the disease, patient age, and the class of drug prescribed. Evidence suggests that drug class may be the main risk factor for the development of an ADR rather than the number of medicines prescribed. A study conducted by Gambacorti-Passerini et al. (2011) found that after a six-year period of treatment with imatinib, 34.3% of patients were affected by a minimum of one mild adverse effect. This increased to a proportion of 52.6% after an eight year treatment period. In a study conducted by Alexopoulou et al. (2007), the team found that 15.7% of ADRs recorded were due to the additive effect of two or more drugs with the same adverse effect profile. This suggests that polypharmacy also plays a significant role in the development of ADRs. The authors concluded that taking several drugs to address various disease states was a major risk factor for ADRs.

Several measures can be taken to minimise the likelihood of an ADR or drug interaction occurring, including:

  • avoiding the prescription of unnecessary medications
  • increasing awareness of the pharmacological mechanisms that contribute to ADRs
  • utilising medication reconciliation, and
  • improving methods for patient reporting of ADRs.

In primary care, the optimisation of patient-doctor communication is vital to ensure the long-term safety and effectiveness of medication therapy. Unfortunately, there are communication gaps in the doctor-patient relationship which Gandhi et al. identified in their 2003 study. They found that 39% of ADRs could be avoided if communication between patients and their doctors was improved. Patients often do not discuss drug-related symptoms with their doctor. This issue may be addressed by increasing the active exploration of ADRs by healthcare professionals (Basch et al., 2006; Richard & Lussier, 2006; Weingart et al., 2005). Fostering rapport between doctors and patients has been shown to influence the frequency of patient symptom reporting. Improving doctor-patient relationships and taking into consideration the patient’s cultural background can facilitate ADR reporting (Miranda et al., 2011). It has also been demonstrated that pharmacist reporting can positively impact upon the quantity of important reports provided by hospitals. Pharmacists can make a significant contribution by assuming a liaison role between patients and other healthcare professionals in the context of adverse event reporting and post-marketing surveillance (Edwards, 1997). Other strategies used to enhance ADR reporting focus on improving prescribing practices. Jaehde et al. (2008) found that the initial and most significant starting point for more effective ADR management is the implementation of evidence-based clinical practice guidelines. This study focussed on ADRs in an oncology setting and was able to demonstrate significant benefits from the use of guideline-based antiemetic prophylaxis.

The knowledge gained by employing pharmacovigilance must translate into patient benefit. Collaboration between all stakeholders, from patients to doctors, pharmacists and other healthcare professionals, will lead to clear communication, accurate information gathering, and ultimately positive patient outcomes.


  1. Alexopoulou A, Dourakis SP, Mantzoukis D, Pitsariotis T, Kandyli A, Deutsch M et al. Adverse drug reactions as a cause of hospital admissions: a 6-month experience in a single center in Greece. Eur J Intern Med. 2008; 19(7): 505-10.
  2. Basch E, Iasonos A, McDonough T, Barz A, Culkin A, Kris MG et al. Patient versus clinician symptom reporting using the National Cancer Institute Common Terminology Criteria for Adverse Events: results of a questionnaire-based study. Lancet Oncol. 2006; 7(11): 903–9.
  3. Bennett CL, Calhoun EA. Evaluating the total costs of chemotherapy-induced febrile neutropenia: results from a pilot study with community oncology cancer patients. Oncologist 2007; 12: 478-83.
  4. Chrischilles EA, Foley DJ, Wallace RB, Lemke JH, Semla TP, Hanlon JT, et al. Use of medications by persons 65 and over: data from the established populations for epidemiologic studies of the elderly. J Gerontol. 1992; 47(5): M137-44.
  5. Doherty MJ. Algorithms for assessing the probability of an Adverse Drug Reaction. Respiratory Medicine CME 2009; 2(2): 63-7.
  6. Edwards R. Adverse drug reactions: finding the needle in the haystack. BMJ. 1997; 315(7107): 500.
  7. Einarson TR. Drug-related hospital admissions. Ann Pharmacother. 1993; 27(7-8): 832-40.
  8. Gambacorti-Passerini C, Antolini L, Mahon FX, Guilhot F, Deininger M, Fava C, et al. Multicenter independent assessment of outcomes in chronic myeloid leukemia patients treated with imatinib. J Natl Cancer Inst. 2011; 103(7): 553-61.
  9. Gandhi TK, Weingart SN, Borus J, Seger AC, Peterson J, Burdick E, et al. Adverse drug events in ambulatory care. N Engl J Med. 2003; 348: 1556-64.
  10. Jaehde U, Liekweg A, Simons S, Westfeld M. Minimising treatment-associated risks in systemic cancer therapy. Pharm World Sci. 2008; 30(2): 161-8.
  11. Lazarou J, Pomeranz BH, Corey PN. Incidence of adverse drug reactions in hospitalized patients: a meta-analysis of prospective studies. JAMA. 1998; 279(15): 1200-5.
  12. Miranda V, Fede A, Nobuo M, Ayres V, Giglio A, Miranda M, et al. Adverse drug reactions and drug interactions as causes of hospital admission in oncology. J Pain Symptom Manage. 2011; 42(3):342-53.
  13. Pirmohamed M, James S, Meakin S, Green C, Scott AK, Walley TJ et al. Adverse drug reactions as cause of admission to hospital: prospective analysis of 18 820 patients. BMJ. 2004; 329(7456): 15-9.
  14. Richard C, Lussier MT. MEDICODE: An instrument to describe and evaluate exchanges on medications that occur during medical encounters. Patient Educ Couns. 2006; 64(1-3): 197-206.
  15. Steinman MA, Hanlon JT. Managing medications in clinically complex elders: “There’s got to be a happy medium”. JAMA. 2010; 304(14): 1592-601.
  16. Weingart SN, Pagovich O, Sands DZ, Li JM, Aronson MD, Davis RB et al. What can hospitalized patients tell us about adverse events? Learning from patient-reported incidents. J Gen Intern Med. 2005; 20(9): 830–6.

Subscribe Knowledge Centre Updates

Enter your details to receive Knowledge Centre updates