Polypharmacy due to multiple physician involvement in patient care increases the risk of serious adverse drug events.
Following our recent polypharmacy campaign, several GPs suggested that this campaign would also benefit their colleagues
in secondary care medicine as many patients return from a hospital stay with multiple additional medications. This is
certainly a valid issue and worthy of further investigation...
Each year in New Zealand, there are approximately 135,000 admissions to hospital for people over the age of 60 years
(NZHIS, 2006). It is inevitable that a significant proportion of these patients will return to their general practice
with additional medications. Polypharmacy messages are most often aimed at the individual primary care provider, however
elderly patients are more likely to have multiple health problems and therefore may see several physicians. Multiple practitioners
managing one patient may unknowingly prescribe duplicate or contraindicated medication regimens. Several overseas studies
have examined the transition of patients between primary and secondary care, specifically in regards to medication. The
most common medication error on admission to hospital is inadvertent withdrawal of a prescribed drug, often due to the
doctor relying on patient recall of their medications (Midlov, 2005). The most common medication error on discharge back
to primary care is the addition of a contraindicated or duplicate medicine (either the same drug as prescribed by the
GP or within the same drug group) (Midlov, 2005).
Ideally admission and discharge notes should include information about what drugs were used prior to hospital care and
what changes have been made. Unfortunately we know this does not always happen and the patient becomes the sole source
of information on medication.
A higher prevalence of medication discrepancies are known to be associated with patients with cardiac conditions. This
may reflect the greater frequency with which medication regimens are adjusted to treat cardiac conditions or it may also
reflect that evidence based treatments often recommend multiple medications (Coleman, 2005).
The most significant issue of polypharmacy involving multiple prescribers is the risk of serious adverse drug events.
There is an increased risk of drug interaction if inappropriate medications are prescribed due to a lack of information
available to the secondary care prescriber.
In a German study involving elderly patients admitted to hospital, 55.6% of patients were being prescribed drugs which
put them at risk for a potential interaction before they were admitted. After discharge, with medication changes from
secondary care physicians, 60.9% were at risk of drug interactions (Kohler 2000).
The risk of potentially inappropriate drug combinations increases with the number of physicians involved in the medical
management of an elderly patient. In a large study involving 65,000 elderly residents of Quebec, it was found that patients
visited a median of three different doctors per year (range 1 to 58) and two thirds had two or more prescribing doctors
(range 1 to 18). The most common medication problems encountered as a result of multiple physician prescribing were concurrent
prescriptions for two benzodiazepines and the prescription of a potassium-sparing diuretic with a potassium supplement.
The patients who had four or more prescribing doctors (21%) had three times the risk of a potentially interacting cardiac
drug combination and two times the risk of a potential NSAID or psychotropic drug reaction (Tamblyn, 1996).
Analysis of pharmaceutical claims data in New Zealand found that almost 50% of over 50 year olds who were consulting
their GP, received five or more medicines over a 6 month period. As the number of prescribing doctors increased, so too
did the number of dispensed medications. A patient with one doctor was prescribed on average four medicines. A patient
with six prescribing doctors received on average 15 medicines (bpacnz, 2006).
The most obvious solution to potentially dangerous polypharmacy occurring as a result of multiple prescribers, is establishing
better communication between primary and secondary care doctors. Ideally, a single GP should take overall responsibility
for managing and coordinating the medication regimen for a patient. In some countries, pharmacists maintain drug profiles
for each patient and use this information to screen for potentially inappropriate prescriptions. Patients are encouraged
to have a single dispensing pharmacist for this purpose (Tamblyn, 1996). This is currently not standard practice in New
Zealand although individual pharmacists may have procedures in place to detect medication discrepancies for their regular
patients.