Medication Errors

Mistakes in the use of a medication are one of the best tracked types
of medical error. Errors with medication can occur in hospitals, at the
pharmacy, in the doctor's office, and even due to the patient. Problems
can include adverse reactions and interactions with other medications, and
also basic administrative errors such as patients being given the wrong
medication or wrong dosage. A less studied aspect of mistakes involving
medications is the misdiagnosis of a disease when the real cause is a
side effect of a medication; see medications underlying disease.

Medication errors: An Institute of Medical report 1 gives detailed
information about deaths and adverse events due to errors in
medication. The report estimates that 7,391 deaths resulted from
medication errors in 1993. The IOM report cites one study finding
that about 2% of hospital admissions experienced a preventable adverse
drug event, although the majority are not fatal. Medication error was
cited as the cause of death for 1 in 131 outpatient deaths and 1 in 854
inpatient deaths.

Children and infants are particularly at risk of medication errors mainly
due to incorrect dosage, because of the need to modify dosages based
on age and weight. The dosage modification may be either overlooked or
miscalculated. Various studies have shown high error rates in doctors and
nurses in calculating weight-dependent dosages in infants and especially
neonates.

Prescription errors: The dispensing of prescription medications at the
pharmacy can have various errors. The wrong medication can be given,
particularly when medications are named or packaged similarly. There are
particular drugs that are known to have problems because their names
are very similar. The pharmacy can also give out the wrong dosage of
the drug in some cases.

Most studies of medication errors only analyzed hospital medication usage,
and there is a large volume of medications prescribed in doctor's offices
and dispensed by pharmacies. There were nearly 2.5 billion prescriptions
dispensed by pharmacies in 1998 in the USA compared to an estimated 3.75
billion drug administrations in hospitals. Errors in prescription and
dispensing are known but difficult to quantify. For example, the IOM
report cites an Australian study for 1988-1996 finding that 2.4 to 3.6
percent of hospital admissions were due to medication events, of which
32 to 69% were preventable. The medications causing most problems were
cytotoxics, cardiovascular drugs, antihypertensives, anticoagulants,
and NSAIDs.

Causes of medication errors: People with kidney conditions, liver
conditions, or known drug allergies were at the greatest risk. The IOM
report cites the following factors as causal in medication errors:

    * failure to alter a medication or dosage due to patient's
    reduced kidney or liver function (13.9%), * known allergy to same
    medication class (12.1%); * using the wrong drug name, dosage form,
    or abbreviation (11.4%), * incorrect dosage calculations (11.1%);
    and * atypical or unusual and critical dosage frequency considerations
    (10.8%).

Data indicates the greatest risk in prescription errors from the doctor
rather than the pharmacist with estimates as follows:

    * prescribing errors (68%), * administration errors (25%) and *
    supply errors (7%).

Adverse drug reactions: An adverse drug reaction (ADR) is not necessarily
a medical error although it can be. An adverse drug reaction occurs
when a patient suffers a reaction, side effect, or other injury from a
medication. This can occur without an error, such as when a patient has
an allergy to a medicine, but has never shown any signs or risk factors
for this allergy previously. On the other hand, an error would occur
if a previous allergy was known but the medication was still given to
the patient.

Adverse drug reactions are quite common. Lazarou et al. 1998 (JAMA)
Lazarou 2 estimated that 6.7% of hospitalizations resulted in an adverse
drug reaction, and 0.32% of cases were fatal. This extrapolates to about
2,216,000 cases annually in hospitalized patients and 106,000 deaths.

Holland et al (1997) 3 estimates as many as 1 million patients are injured
while in the hospital and approximately 180,000 die as a result. This
leads to a cost estimate of more than $136 billion a year. The article
cites the list of medications most frequently causing adverse reactions
in order of incidence:

    * antibiotics, * chemotherapy, * anticoagulants, * cardiovascular
    agents, * anticonvulsants, * antidiabetic agents, * antihypertensives,
    * analgesics, * antiasthma agents, * sedative-hypnotic agents, *
    antidepressants, * antipsychotic agents, and * antiulcer agents.


Footnotes: 1. Institute of Medicine (IOM), "To Err Is Human: Building
a Safer Health System", 2000,online.  2. Lazarou J, Pomeranz BH, Corey
PN. Incidence of adverse drug reactions in hospitalized patients: a
meta-analysis of prospective studies. JAMA 1998 Apr 15;279(15):1200-5,
html, PDF 3. EILEEN G. HOLLAND, PHARM.D., and FRANK V. DEGRUY,
M.D. Drug-Induced Disorders, Volume 15, No. 7, November 1, 1997, html