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Splitting tablets |
Summary
Patients split tablets for a variety of reasons, however there are problems associated with this process. Tablet-related factors include inaccuracy in splitting tablets and the resultant dose fluctuations, increased degradation of drug as a result of exposure to air and alterations in the dissolution rate of some formulations. Even when commercial tablet cutters are used the accuracy of splitting may be variable. Patients may experience difficulty in splitting tablets especially if their dexterity, eyesight or cognition is impaired. Compliance is likely to be decreased if the regimen requires tablets to be split. Although splitting tablets may potentially save the patient money the possible impact on the quality of medication use must be considered.
Key words: compliance, dosing, quality use of medicines.
(Aust Prescr 2002;25:133-5)
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Introduction
Tablet splitting or dividing has been an accepted practice for many years as
a means of obtaining the prescribed dose of a medication. Patients may be required
to split tablets to:
• obtain the required dosage when a dosage form of the required strength
is unavailable
• provide appropriate fractional doses in a flexible dosing regimen or
in a gradually increasing or decreasing dosage regimen
• begin therapy with the lowest possible dose to decrease the incidence
of adverse effects or to gauge an individual patient's response.
Elderly people or children who require reduced doses may not be able to use
liquid formulations (or they may not be available on the Pharmaceutical Benefits
Scheme). If suitable low-dose tablet formulations are unavailable, these patients
may require tablets to be split to obtain the appropriate dosage.
Patients may save money if there is a price differential that makes halving
tablets economically attractive. However, the process of splitting tablets causes
a number of problems, some of which are patient-related while others are related
to the tablet or formulation.
Tablet or formulation-related factors
Uneven breaking of a tablet may result in significant fluctuations in the administered
dose. This may be clinically significant for drugs with a narrow therapeutic
range1, such as warfarin
or digoxin. For many drugs, however, especially those with long half-lives and/or
a wide therapeutic range, dose fluctuations are unlikely to be clinically significant.
Removing tablets from foil packaging or exposing uncoated tablet surfaces may
increase the rate of degradation of the active drug. This has important ramifications
as the patient may get a lower than intended dose and adverse effects may be
increased by degradation products. The tablet dissolution rate and absorption
characteristics may also be affected when tablets are split.2
This applies particularly to coated and controlled-release tablets. While the
cumulative dissolution may be similar between whole and halved tablets the initial
rate of dissolution may be increased with unpredictable clinical consequences.
Some sustained-release (extended duration) formulations can be halved without
affecting their extended-release characteristics (e.g. isosorbide mononitrate,
bupropion) while others cannot (e.g. felodipine (Agon SR), tramadol (Tramal
SR)) and it is therefore important to check the product information of each
specific brand if splitting tablets is considered. Many tablets are coated to
mask the taste of the drug. Splitting may therefore expose a drug's taste. Table
1 provides a general guide, with limited examples, as to which tablets may
not be suitable for splitting.
Tablets that are scored are usually considered by the manufacturer to be suitable
for division and the majority of tablets are made this way. Not all tablets,
however, are suitable for splitting and this should be considered when the recommendation
to split the tablet is made. The degree of inaccuracy may be associated with
tablet size, shape and type of scoring (Table 2). Some tablets,
even with a score line, may not break easily into two pieces of equal size.1
The length of time that drugs remain stable after splitting also needs to be
considered as the drug may not be stable when the cut surface is exposed to
air for even short periods (up to 24 hours) let alone tablets pre-cut for doses
a week or more in advance. This may be of importance if a carer, district nurse
or pharmacist has to split tablets in advance for patients unable to manage
the task.
The storage of split tablets is not well discussed in the literature. Anecdotal
evidence suggests that many patients, or their carer, nurse or pharmacist, split
a number of tablets in advance. Patients store split tablets in bottles that
previously contained the same medication, different medication or some other
substance, or in the same bottle as whole tablets or in a dosage administration
aid. Issues of concern relate to labelling of storage containers and the time
that split tablets are exposed to air and light before use with the possible
detrimental effect on stability. For example the instability of soluble aspirin
limits the usefulness of the unused half of a split tablet. If only half the
tablet is taken the unused half should be immediately discarded.
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Patient-related factors
Tablets can be split manually into two portions by either breaking with the
fingers along a scored line, cutting with a knife or using a specially designed
tablet cutter. Substantial dexterity in positioning and holding the tablet is
needed. Uneven division of the tablet or a degree of wastage can occur as some
tablets may crumble or break into more than two parts.
Commercially available tablet cutters should increase the accuracy of tablet
splitting, but these devices require a degree of manual dexterity in loading
the tablet.3 Irregularly
shaped tablets may be difficult to load and may not easily be split into equal
halves. Dividing a tablet into quarters is even more difficult and is likely
to incur a greater rate of tablet wastage and inaccuracy in final dosage.4
Liquid formulations may not be suitable alternatives for elderly patients as
measuring volumes of liquid formulations also requires dexterity and good eyesight.
These formulations also preclude the use of dosage administration aids such
as dispenser packs. Splitting tablets may be the only option when a reduced
dose is needed.
Old age or diseases such as arthritis and Parkinson's disease can cause impaired
manual dexterity or decreased grip strength that renders the process of splitting
tablets extremely difficult.5
Even if a tablet cutter is used it may not improve accuracy if the patient is
functionally impaired. Cognitive impairment may make remembering instructions
to split a tablet for a particular dose difficult, especially if dosage regimens
are complex, such as tapering or increasing doses, or if more than one tablet
is to be split.
Another issue of concern is whether difficulty splitting tablets may adversely
affect patient compliance with drug regimens, as patients may skip or double
doses rather than split tablets and retain unused halves. Complex regimens involving
split tablets may be expected to decrease patient compliance. Studies have shown
that patient compliance is not decreased by use of split tablet regimens6,7,
although the results should be interpreted with caution because of selection
bias.
Cost considerations
While splitting tablets may appear cost-effective, there may be adverse consequences
relating to the treatment of the patient's condition. Any savings from splitting
tablets may be offset by drug wastage and potential negative effects on the
quality use of medicines.
Conclusion
The decision to split tablets should be made after due consideration. The following
recommendations may be used as a guide:
• Check the product information before recommending tablets be split
• In general only scored tablets should be split
• Patients should be assessed for their ability to understand and comply
with regimens involving split tablets
• A tablet cutter can be used to improve accuracy, but patients must be
instructed in its proper use
• Patients should be advised about appropriate storage of split tablets.
References
1. McDevitt JT, Gurst AH, Chen Y. Accuracy of tablet splitting.
Pharmacotherapy 1998;18:193-7.
2. Mandal TK. Effect of tablet integrity on the dissolution
rate of sustained-release preparations. J Clin Pharm Ther 1996;21:155-7.
3. Carr-Lopez SM, Mallett MS, Morse T. The tablet splitter:
barrier to compliance or cost-saving instrument? Am J Health Syst Pharm 1995;52:2707-8.
4. Horn LW, Kuhn RJ, Kanga JF. Evaluation of the reproducibility
of tablet splitting to provide accurate doses for the pediatric population.
J Pediatr Pharm Pract 1999;4:38-42.
5. Atkin PA, Finnegan TP, Ogle SJ, Shenfield GM. Functional
ability of patients to manage medication packaging: a survey of geriatric inpatients.
Age Ageing 1994;23:113-6.
6. Fawell NG, Cookson TL, Scranton SS. Relationship between
tablet splitting and compliance, drug acquisition cost, and patient acceptance.
Am J Health Syst Pharm 1999;56:2542-5.
7. Rindone JP. Evaluation of tablet-splitting in patients
taking lisinopril for hypertension. J Clin Outcomes Manage 2000;7:22-4.
Conflict of interest: none declared
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