J R Soc Med 2004;97:328-329
doi:10.1258/jrsm.97.7.328
© 2004 Royal Society of Medicine
Keep in a cool place: exposure of medicines to high temperatures in general practice during a British heatwave
Brian Crichton BSc MRCGP
Hobs Moat Medical Centre, Ulleries Road, Solihull B92 8ED, UK
E-mail:
bcrichton{at}dial.pipex.com
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SUMMARY
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Exposure of medicines to high temperatures in storage or in
transit could
reduce their efficacy, and most licences specify
storage at 25°C or less.
To assess whether this criterion
was being met, maximum temperatures in a
general practice drug
cupboard and in drug bags placed in car boots were
recorded
for two weeks during a British heatwave (average peak daily
ambient
temperature 26°C). Also, ten neighbouring dispensing
pharmacies were
questioned about their temperature-control policies.
On every day of the study, maximum temperatures in the drug cupboard and in
the car boots exceeded 25°C. Mean daily maxima (range) were: drug cupboard
30.7 (27.5-37.0); silver car 37.5 (32.0-43.5); dark blue car 41.8 (35.0-49.5).
None of the local dispensaries had air conditioning or kept a temperature
log.
In the course of a British summer, medicines were exposed to temperatures
that might in theory have reduced their efficacy. This aspect of quality
control deserves more attention.
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INTRODUCTION
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Family doctors in the UK store medicines either on practice
premises or in
bags for emergency use on home visits. Manufactured
drugs, in general, are
licensed for storage at temperatures
up to
25°C.
1 At higher
temperatures there is the risk that
their efficacy will be adversely affected,
and the quality of
drugs carried by family doctors for emergency use—for
example,
benzylpenicillin for suspected bacterial meningitis—needs
to be
above suspicion.
Box 1 lists
some of the agents commonly
carried in this way.
The temperature conditions of medicines were investigated in a suburban
primary care setting during an English heatwave.
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METHODS
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Three mercury maximum/minimum thermometers were purchased and
checked by
comparison of maximum temperatures recorded after
24 hours on the same shelf
of the practice drugs cupboard. They
agreed within 0.5°C. Two of the
thermometers were then put
in doctors' bags (Gladstone, burgundy coloured),
which in turn
were placed in the boots of two cars (A, silver coloured; B,
dark
blue), which occupied similar positions in the car park. The
third
thermometer was installed on the top shelf (41 cm below
ceiling height) of a
locked metal drugs cupboard in the practice
treatment room. The day's maximum
temperature was recorded at
1900 h each day from 4 to 15 August 2003,
inclusive—a
time of warm weather. Over the same period, the maximum
ambient
air temperature at the Coleshill Weather Station, 8 km from
the
practice, was obtained from the national UK meteorological
website.
On 13 August the ten geographically closest dispensing pharmacies were
contacted by telephone and were asked: Does your dispensary have air
conditioning? Do you measure temperatures in your dispensary?
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RESULTS
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Table 1 shows the maximum
temperatures for the drugs cupboard
and the boots of the two cars, together
with maximum ambient
air temperatures during the days of the study. On every
day,
at every drug storage site, temperatures exceeded 25°C.
The telephone
survey indicated that none of the ten local pharmacies
had air conditioning or
monitored dispensary temperatures.
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DISCUSSION
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The journey of a medicine begins at the site of manufacture
and passes
through warehouses, pharmacies, and sometimes other
environments before
reaching the end user. Temperature conditions
in the earlier stages have
received attention, but little work
has been done in primary care settings and
community pharmacy
settings in the UK. A previous study, by Rudland and
Jacobs,
2 did draw
attention to high temperatures in the boots of doctors'
cars. The findings of
the present study suggest that temperature
quality control in primary care and
community pharmacies (if
ours are typical) leaves much to be desired. Where
air conditioning
is not standard practice, medicines are at the mercy of the
ambient
temperature; and conditions in car boots are particularly disturbing.
The
difference between the cars was of interest: although the vehicles
were
not identical models, the paint colour was probably the
relevant feature: car
B was dark blue, and more likely to absorb
heat than the silver car A.
In all three environments, drugs were exposed to temperatures exceeding
25°C. Do these deviations from the recommended storage temperatures matter
in practice? Looking at one of the drugs commonly carried, adrenaline, Rudland
and co-workers found no significant alterations in activity by high ambient
temperatures.3,4
However, some other products do seem temperature sensitive. For example, the
capsules of certain brands of cefalexin degraded more rapidly in hot
conditions and this caused ‘serious fluctuations’ in
absorption.5
Ampicillin, erythromycin, furosemide for injection and benzylpenicillin
stored in a tropical climate showed significant reductions in activity at one
year.6 Aspirin
follows first-order kinetics with regard to temperature degradation, and a
similar finding was recorded for diclofenac tablets exposed to high ambient
temperatures (dissolution rate was reduced significantly in as little as three
months, with resultant reduction in maximum plasma concentration
achieved).7
There is a duty to ensure that medicines are kept in an environment that
maintains their efficacy. The manufacturer will be responsible for
shortcomings only if storage has occurred as stipulated in the Summary of
Product
Characteristics.8 In
almost all cases the specified temperature is 25°C or less. The effect of
temperature is seen in the rate of oxidation or hydrolysis: for every 10°C
increase in temperature there is generally an exponential increase in the rate
of reaction.9 (Drug
stability can also be affected by low temperatures, especially liquid
preparations liable to freezing.)
This research highlights some important areas in medicines management.
Manufacturers need to offer more drug stability data in relation to
temperature. Even if the immediate stability of stored medicines is not
seriously affected there may well be an effect on shelf life or expiry date.
To rectify this, practices and pharmacies may have to consider arrangements
for cooling. As to the carriage of medicines by healthcare professionals in
their cars, simple precautions are to avoid leaving drug bags in the boot or
to use cool bags.
The present observations, though made in exceptional weather conditions for
the English Midlands, highlight the need for further work on storage
conditions for medicines in primary care and in community pharmacies.
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REFERENCES
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