| Background:
Human insulin was introduced for the routine treatment
of diabetes mellitus in the early 1980s without adequate comparison
of efficacy to animal insulin preparations. First reports
of altered hypoglycaemic awareness after transfer to human
insulin made physicians and especially patients uncertain
about potential adverse effects of human insulin.
Objectives:
To assess the effects of different insulin species by
evaluating their efficacy [in particular glycaemic control]
and adverse effects [mainly hypoglycaemia].
Search Strategy:
A highly sensitive search for randomised controlled trials
combined with key terms for identifying studies on human versus
animal insulin was performed using the Cochrane Library [Issue
2, 2002], Medline [1966 to May 2002]. We also searched reference
lists and databases of ongoing trials. Date of last search:
May 2002
Selection criteria:
We included randomised controlled trials with diabetic patients
of all ages that compared human to animal [for the most part
purified pork] insulin. Trial duration had to be at least
one month in order to achieve reliable results on the main
outcome parameter glycated haemoglobin.
Data collection and analysis:
Trial selection as well as evaluation of study quality was
performed by two independent reviewers. The quality of reporting
of each trial was assessed according to a modification of
the quality criteria as specified by Schulz and by Jadad.
Main results:
Altogether 2156 participants took part in 45 randomised controlled
studies that were discovered through extensive search efforts.
Though many studies were of a randomised, double-blind design,
most studies were of poor methodological quality. Purified
porcine and semi-synthetic insulin were most often investigated.
No significant differences in metabolic control or hypoglycaemic
episodes between various insulin species could be elucidated.
Insulin dose and insulin antibodies did not show relevant
dissimilarities.
Reviewers’ conclusions:
A comparison of the effects of human and animal insulin as
well as of the adverse reaction profile did not show clinically
relevant differences. Many patient-oriented outcomes like
health-related quality of life or diabetes complications and
mortality were never investigated in high quality randomised
clinical trials. The story of the introduction of human insulin
might be repeated by contemporary launching campaigns to introduce
pharmaceutical and technological innovations that are not
backed up by sufficient proof of their advantages and safety.
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What does this review of
‘human’ and animal insulin mean for people with
diabetes?
It provides us with information to make truly
informed choices about the species of insulin we wish to use.
Our choices are simple - animal insulins with a history of
70 years research and post marketing surveillance [being used
in the real life situation for over 70 years] or ‘human’
insulin with an absence of meaningful research and an ongoing
history of reported adverse reactions.
The review has dispelled many of the myths
that are told to people with diabetes.
- It can no longer be said that ‘human’
insulin is better than animal insulins, because there is
no evidence for this.
- It can no longer be said that ‘human’
insulin gives better control and better HbA1cs, there is
no evidence for this.
- It can no longer be said that ‘human’
insulin produces less antibodies, there is no evidence to
support this.
- The existence of other adverse effects,
apart from hypoglycaemia, was not even investigated, so
their existence can no longer be denied.
Important issues for people treated with
insulin have never been investigated
Perhaps the greatest importance
of this review is that it highlights the research that has
NEVER been carried out. This absent research is essential
for us to know that we are being treated with the insulin
that produces the best effects on our health, our wellbeing
and indeed our lives and even our life expectancy. These are
very basic requirements for any drug but perhaps especially
so for ‘human’ insulin - the first ever genetically
produced drug to be used on human beings. Twenty years after
its arrival on the market with indecent haste, ‘human’
insulin has never been subjected to essential, quality post
marketing research to answer the questions that must now be
asked by people who are prescribed it.
About Cochrane reviews:
Information about the Cochrane Collaboration and systematic
reviews
It is an international non-profit
organisation that aims to help people make informed decisions
about health care by reviewing and promoting the best available
evidence from research on the effects of various treatments.
The Collaboration also aims to influence what the direction
of future research by identifying areas where more research
is needed.
We are all aware that some
health care treatments make you better, some don’t and
sometimes the treatment can be even worse than the condition.
Sometimes it seems as though a drug/treatment worked, but
really the benefit came from something else or maybe you would
have just got better anyway. So both patients and doctors
need good evidence from research to know the effects of a
drug or treatment in order to decide whether we should try
it. This also applies to decision-making bodies, such as the
NHS.
How is this good
evidence acquired?
However good individual studies maybe, they are often carried
out on specific groups of people or on small numbers so the
results cannot be extended to assume that the effects of the
treatment will be the same for everyone with a particular
condition. Publication bias also creeps in as a great deal
of good research is not published and so we are not receiving
the complete picture.
Cochrane groups carry
out systematic searches for all the studies on a topic and
then sort out which are the good quality studies [randomised
controlled trials or RCTs]. Conclusions can then be drawn
that give a much more complete picture of whether or not a
drug/treatment is effective. A review may show that there
is no evidence to support a particular drug/treatment or that
little or no good quality research has been carried out. This
is equally important because it means that the use or prescribing
of that drug/treatment is not based on proven benefit from
research.
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