January/February 2009 - Ontario College of Pharmacists

focus on error prevention
Pediatric dosages
Ian Stewart, R.Ph., B.Sc.Phm
Toronto Community Pharmacist
When checking prescriptions, pharmacists must consider
the appropriateness of the dosage being prescribed.
This can only be done if the pharmacist
is aware of, or considers the indication for use or purpose of the
medication being prescribed. For example, when codeine is
prescribed for the treatment of acute pain, the reccommended
adult dosage is 15 to 60 mg orally every four to six hours. 1 However,
when used as a cough suppressant, the recommended
dosage is 5 to 20 mg orally every four to eight hours.2 Yet, the
indication for use or purpose of the medication is not usually
included on prescriptions. This missing piece of information is
often a contributing factor to medication errors.
Case:
prescription, the pharmacist on this occasion observed that the
dosage was not consistent with the usual dosage used in the
treatment of herpes labialis or other common viral infections.
The original prescription was therefore checked to confirm the
prescriber’s intent. On checking the original prescription, the
dosing error was identified. The correction was made, and
the patient given eight Valtrex® 500 mg tablets with instructions
to take four tablets (2000 mg) twice daily. The patient
was very upset upon hearing of the error. She stated that she
“thought something was wrong, and questioned the pharmacist.”
Unfortunately, the pharmacist at that time read the prescription
and reassured the patient that the physician did indeed
prescribe two tablets twice daily.
Possible Contributing Factors:
• The pharmacy stocked the 500 mg strength of Valtrex® and
not the 1000 mg.
• The technician failed to adjust the directions for use to compensate
for the change in strength.
• The indication for use or purpose of the medication was not
included on the prescription.
• The initial pharmacist did not consider the possible indication
for use to ensure appropiateness of the dose.
• Despite concerns raised by the patient, the pharmacist
failed to double check all components of the prescription for
accuracy.
The above prescription was written for a patient for the
treatment of cold sores (herpes labialis). The prescription
was taken to a local pharmacy for processing.
On entering the prescription into the computer, the pharmacy
technician entered Valtrex® 500 mg tablets. However,
the directions for use was not adjusted and therefore entered
as two tablets twice daily. When checking the prescription,
the pharmacist did not detect the error. A total of four Valtrex®
500 mg tablets were therefore dispensed instead of four
1000 mg tablets or eight 500 mg tablets with the appropiate
instructions for use.
A few months later, the patient requested a refill of the Valtrex®
tablets. A pharmacy technician processed the refill and
gave it to the pharmacist for checking. On checking the refill
Recommendations:
• Whenever possible, dispense the same strength or concentration
of the medication as prescribed. The directions for use
would therefore be the same given to the patient by the prescriber.
Clearly explain any changes to the patient.
• Always consider the possible indication for use when checking
prescriptions for appropiateness and accuracy.
• Investigate thoroughly all concerns raised by the patient.
• Appropiate steps should be taken by all stakeholders to ensure
that the indication for use or purpose of the medication
is included on all prescriptions. This is certainly a patient
safety issue.
References:
1. Gray J, Therapeutic Choices, Canadian Pharmacists
Association Ottawa ON 2007;207
2. Gray J, Therapeutic Choices, Canadian Pharmacists
Association Ottawa ON 2007;1535
16 pharmacyconnection • January/February 2009