|
ABC of Diabetes
by Peter J. Watkins
Insulin treatment
I was like a dried tree, but you have given me new life.
An Ethiopian villager, after starting insulin.
The astonishing power of insulin to restore health and
wellbeing to rapidly deteriorating newly diagnosed Type 1
diabetic patients is as remarkable now as it was in 1922.
After Banting gave insulin to Elizabeth Hughes in that year,
she wrote to her mother that “it is simply too wonderful for
words this stuff.” Insulin to this day always has this
effect; the challenge now is to optimise control in order to
maintain health throughout life.
Insulin is also needed to
enhance well-being and control in many Type 2 diabetic
patients when the natural progression of their disease has
lead to loss of optimal control. The potential to reduce the
development of long-term diabetic complications as
demonstrated by the UKPDS (see page 42) has led to a recent
explosion in conversions from tablets to insulin. The
difficult decisions which surround the need for insulin in
this situation, together with benefits, uses and misuses of
insulin have been described in the previous chapter.
The use of insulin must be
tailored to meet individual requirements. The aim is to
achieve the best possible control in the circumstances,
avoiding at all costs the disabling hypoglycaemia which can
occur if control is excessively tight. In some elderly
patients and those who lack motivation, it is therefore wise
to aim only at alleviating symptoms and not to attempt very
strict control.
Types of insulin
Soluble insulins
These were first introduced in 1922. They have a rapid onset
of action (within 15-30 minutes) and a relatively short
overall duration of action of six to eight hours. They play
an important part in both daily maintenance of diabetic
patients by subcutaneous injection, and also in managing
emergencies, when they can be given intravenously or
intramuscularly. Other insulin preparations are not suitable
for intravenous or intramuscular use.
New recombinant insulin analogues
These have a very rapid onset and very short action, and
have been developed by altering the structure and thus the
property of the insulin. The preparations available in the
United Kingdom at present are Insulin Lispro (Humalog) and
Insulin Aspart (Novo Rapid). They have some advantages
because they may be given immediately before meals (or even
immediately after meals if necessary). By virtue of their
very short action, there is less hypoglycaemia before the
next meal, and when they are used before the main evening
meal nocturnal hypoglycaemia is effectively reduced.
There is a risk of
postprandial hypoglycaemia if they are used before a meal
with a very high fat content because of the delayed gastric
emptying. Duration of action is short and does not normally
exceed three hours, and their use is therefore inappropriate
if the gap between meals exceeds about four hours.
Preprandial blood glucose levels are slightly higher than
with conventional soluble insulins.
They are also ideal for use in continuous subcutaneous
insulin infusion pumps (CSII).
Protamine insulins
These are medium duration insulins introduced in Denmark
during the 1930s. Isophane insulin is the most frequently
used insulin in this group.
Insulin zinc suspensions
These were first introduced during the 1950s; there are
several preparations with widely ranging durations of
action. There are limited indications for using insulins
with a very long duration of action (ultratard).
Insulin glargine
This is a new prolonged action, soluble insulin analogue
(clear solution) forming a microprecipitate after
subcutaneous injection. Its onset of action is after about
90 minutes, it has a prolonged plateau rather than a peak,
and lasts 24 hours or more. Thus it mimics more closely the
basal insulin secretion of healthy people. When taken at
bedtime it reduces the incidence of nocturnal hypoglycaemia,
and also reduces the prebreakfast hyperglycaemia. It does
not appear to reduce symptomatic or severe hypoglycaemia
during the day, and there is no significant beneficial
effect on overall diabetic control. More extensive clinical
experience in using this insulin is still needed.
Note: The rest of the chapter
is omitted.
|
