Erroneous Prescription of Half Tablets in a Swiss University Hospital

Abstract

Introduction: Prescription of ½ tablets is a widespread practice, mainly for dose flexibility, ease of swallowing, and cost reduction. However, tablet splitting includes several disadvantages, like destruction of galenic formulation, stability problems, and unequal amount of active ingredient that may reduce effectiveness or result in a greater risk of toxicity.
Aims: The aim of this retrospective analysis was to assess the rate of erroneously prescribed ½ tablets in discharge prescriptions at the University Hospital in Basel (UHBS, 600 beds), and to evaluate its consequences for community pharmacists.
Methods: Discharge prescriptions with the term “½” were extracted from the electronic patients’ data management system of the UHBS between January 1st and December 31st 2011. Presence of a score line and suitability for splitting were retrieved from two sources of drug information.1,2 Erroneous prescription was assigned for drugs that had no score line, were not suitable for dose splitting, or without information.
Results: Of the 36,751 discharge prescriptions that were recorded in 2011 at the UHBS, 3,724 (10.1 %) contained at least one prescription item with the term “½”. The recipient patients were on average 72.9 ± 14.8 years old (median 76 years), 50.9 % were women. After exclusion of 371 items (not a tablet, not available in Switzerland, major writing errors, missing strength, off the market) 4,517 items were analysed. For 49 % of them, the prescribed splitting was unnecessary because of the availability of adequate dosage strength. Most prescribed ½ tablets were scored (87 %) and suitable for dose splitting (77.6 %). Erroneous prescription rate of ½ tablets was 22.4 % (inexistent score lines (12.6 %); clear ban in the sources of drug information (3.8 %), lack of information (6.1%) and concerned 2.8 % of all prescriptions. Half of all erroneous prescriptions could be assigned to 14 different products that were prescribed with an overall rate between 3.06 and 0.27 %. Seroquel® (Quetiapin) at all strengths was the most often erroneously prescribed tablet to split (3.1 %; no score line), followed by Sortis® (Atorvastatin) at all strengths (1.3 %; no score line) and Seresta® (Oxazepam) 15mg (1.2 %; decorative score line).
Conclusions: Prescribing of ½ tablets is a common issue, affecting 10.1 % of all discharge prescriptions of the UHBS. However, every 5th prescription with ½ tablets is erroneous. Prescription of ½ tablets is a pharmaceutical care issue. Community pharmacists have to detect and to handle prescription errors which is amongst their core competences. In many cases, tablets of half the dosage are commercially available and pharmacists can offer a substitution. In all cases, time consuming and costly clarifications must be undertaken, ultimately the physician must be consulted, in order to modify the prescription or to dispense the prescribed ½ tablets as off-label use. If splitting is allowed, the patient’s cognitive and physical capacities have to be clarified and appropriate aids have to be offered, e.g. a pill splitter.

References:
[1] www.compendium.ch (last accessed May 2012).
[2] www.spitalpharmazie-basel.ch/pdf/Zermoerserbarkeit_Tabletten.pdf (last accessed May 2012).

Full text

electronic discharge
prescriptions at the UHBS
in 2011
n=36’751
prescriptions with “½”
n=3’724 (10.1%)
single items with “½”
n=4’888
prescribed ½ tablets
n=4’717
excluded (n=171):
• non identifiable
(n=22)
• foreign products
(n=68)
• other formulation
than tablet (n=81)
full information available
n=4’517 (100%)
excluded (n=200):
• no strength (n=125)
• not existing strength
(n=68)
• off market (n=7)
with score line
n=3‘928 (87%)
no information about
score line
n=21 (0.5%)
no score line
n=568 (12.6%)
suitable for splitting
n=3‘503 (77.6%)
no information
about splitting
n=252 (5.6%)
not suitable for splitting
n=173 (3.8%)
prescription items with “½”
n=34’307
Erroneous Prescription of Half Tablets
in a Swiss University Hospital
I. Arnet1, F. Böni1, M. von Moos1, C. Aeschlimann1, K.E. Hersberger1
1Pharmaceutical Care Research Group, University of Basel, Basel, Switzerland
Corresponding author:
isabelle.arnet@unibas.ch
Pharmaceutical Care Research Group, Klingelbergstrasse 50
CH-4056 Basel (Switzerland)
Download: www.pharmacare.unibas.ch
Background
Prescription of ½ tablets is a widespread practice with the following
• advantages:
+ dose exibility + ease of swallowing + cost reduction
• and inconvenients:
- destruction of galenic formulation - stability problems
- unequal amount of active ingredient
with consequences of reduced effectiveness or greater risk of toxicity.
Objectives
• to assess the rate of prescribed ½ tablets in discharge prescriptions
at the University Hospital in Basel (UHBS, 600 beds);
• to evaluate its consequences for community pharmacists.
Methods
• Discharge prescriptions between January 1st and December 31st 2011
that contained the term “½” were extracted from the electronic patients’
data management system of the UHBS
• The presence of a score line and the suitability for splitting was assessed
and classied according to two sources of drug information1,2 (Table 1)
• Erroneous prescription was assigned for drugs that were without a score
line, not suitable for dose splitting, or with no information.
Results
Of the 36’751 discharge prescriptions that were recorded in 2011 at the
UHBS, 4’888 contained a single prescription line with “½”. After exclusion
of 371 items, 4’517 items were analysed (Figure 1).
Splitting rate:
• 10.1% of all prescriptions contained the term “½”
• 22.4% of the single prescriptions of ½ tablets were erroneous
• this represents 2.8% of all discharge prescriptions.
• Splitting was unnecessary for 49% of the prescribed ½ tablets because
of available lower strength on the market.
In-depth analysis:
• 50% of all erroneous prescriptions could be assigned to 14 different
products that were prescribed with a rate of 3.06-0.27% (Table 2).
• Seroquel® (quetiapine) at all strengths was the most often erroneously
prescribed tablet to halve (3.1%; no score line), predominantly due to
Seroquel® 25mg (2.5%).
Product
brand name
Active
substance(s)
Prescribed
strength
Total
prescription
rate [%]
Score
line*
Ban*,§
Seroquel®,
Seroquel XR®
quetiapine 25, 50, 100, 200,
300, 400mg
3.06 no
Sortis® atorvastatin 10, 20, 40, 80mg 1.31 no
Seresta®oxazepam 15mg 1.20 yes yes
Aldactone®spironolactone 25, 50, 100mg 1.00 no
Norvasc®amlodipine 5, 10mg 0.84 no
Zyloric®allopurinol 100, 300mg 0.69 yes yes
Risperdal®risperdione 0.5 / 1/2mg 0.53 yes yes
Co-Aprovel®irbesartan / HCT 150 / 12.5,
300 / 12.5mg
0.42 no
Aprovel®irbesartan 150, 300mg 0.40 no
Zestril®lisinopril 10, 20mg 0.40 no
Nexium®esomeprazole 20, 40mg 0.38 no
Lamictal®lamotrigine 25, 50, 100,
200mg
0.38 no
Remeron®mirtazapine 15, 45mg 0.31 no
Haldol®haloperidol 1mg 0.27 yes yes
Table 2: Most frequently erroneously prescribed ½ tablet; HCT: hydrochlorothiazid;
*drug information from1, 2 §sentences explicitely forbitting tablet splitting
Discussion and Conclusion
• Every 5th discharge prescription with ½ tablet is erroneous, resulting in
unnecessary work for the pharmacists who need to resolve the
uncertainty about the prescription.
• In almost half of the cases, tablets of lower dosage strength are commer-
cially available and pharmacists can offer a substitution.
• In all cases, the physician must be consulted in order to modify the
prescription or to dispense the prescribed ½ tablets as off-label use.
• If splitting is allowed, the patient’s cognitive and physical capacities have
to be claried and appropriate aids have to be offered, e.g. a pill splitter.
• Prescription of ½ tablets is a major pharmaceutical care issue.
References
[1] www.compendium.ch (last accessed May 2012)
[2] www.spitalpharmazie-basel.ch/pdf/Zermoerserbarkeit_Tabletten.pdf (last accessed May 2012)
GSASA congress 2012
Baden, Switzerland
November 15-16, 2012
Score line Splitting suitability
tablet with a score line suitable for dose splitting
tablet with no score line not suitable for dose splitting
no information about score line no information about splitting
Table 1: Tablets’ classication according to1,2
Figure 1: Discharge prescriptions written in 2011 at the University Hospital Basel with
sebsequent analysis of the suitability to split tablets