Hypoglycaemia : This is the most frequent and potentially the most serious reaction. It is commonly seen in patients of ‘labile’ diabetes in whom insulin requirement fluctuates unpredictably.
REACTIONS TO INSULIN
This is the most frequent and potentially the most serious reaction. It
is commonly seen in patients of ‘labile’ diabetes in whom insulin requirement
fluctuates unpredictably. Hypoglycaemia can occur in any diabetic following
inadvertent injection of large doses, by missing a meal or by performing vigorous
exercise. The symptoms can be divided into those due to counterregulatory
sympathetic stimulation— sweating, anxiety, palpitation, tremor; and those due
to deprivation of the brain of its essential nutrient glucose (neuroglucopenic
symptoms) — dizziness, headache, behavioural changes, visual disturbances,
hunger, fatigue, weakness, muscular incoordination and sometimes fall in BP.
Generally, the reflex sympathetic symptoms occur before the neuroglucopenic,
but the warning symptoms of hypoglycaemia differ from patient to patient and
also depend on the rate of fall in blood glucose level. After longterm
treatment about 30% patients lose adrenergic symptoms. Diabetic neuropathy can
abolish the autonomic symptoms. Hypoglycaemic unawareness tends to develop in
patients who experience frequent episodes of hypoglycaemia.
Finally,
when blood glucose falls further (to < 40 mg/dl) mental confusion, abnormal
behaviour, seizures and coma occur. Irreversible neurological deficits are the
sequelae of prolonged hypoglycaemia.
Treatment Glucose must be given orally or i.v. (for severe cases)—reverses the symptoms
rapidly. Glucagon 0.5–1 mg i.v. or Adr 0.2 mg s.c. (less desirable) may be
given as an expedient measure in patients who are not able to take sugar orally
and injectable glucose is not available.
Swelling, erythema and stinging sometimes
occur especially in the beginning. Lipodystrophy
occurs at injection sites after long usage. This is not seen with newer
preparations—which may even facilitate reversal of lipoatrophy when injected at
the same sites.
This is infrequent; is due to contaminating proteins; very rare
with human/highly purified insulins.
Urticaria,
angioedema and anaphylaxis are the manifestations.
Some patients develop shortlived dependent edema (due
to Na+ retention) when insulin therapy is started.
1) β adrenergic blockers prolong hypoglycaemia by inhibiting
compensatory mechanisms operating through β2 receptors (β1 selective agents are
less liable). Warning signs of hypoglycaemia like palpitation, tremor and
anxiety are masked. Rise in BP can occur due to unopposed α action of released
Adr.
2)
Thiazides, furosemide, corticosteroids, oral
contraceptives, salbutamol, nifedipine tend to raise blood sugar and reduce
effectiveness of insulin.
3)
Acute ingestion of alcohol can precipitate
hypoglycaemia by depleting hepatic glycogen.
4)
Salicylates, lithium and theophylline may also
accentuate hypoglycaemia by enhancing insulin secretion and peripheral glucose
utilization.
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