PARACETAMOL:
HOW SAFE IS MY PAINKILLER?
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Paracetamol sales surge
each year across India, during seasonal flu, dengue and chikungunya outbreaks,
because it is the safest drug for fever and pain. Compared to aspirin and other
popular NSAIDS (non-steroidal antiinflammatory drugs that treat pain and
inflammation) such as ibuprofen and naproxen, it has fewer side effects and
does not raise the risk of bleeding associated with dengue and fevers of
unknown origin.
What most people don’t
know is that paracetamol (acetaminophen in the US and Canada) overdose, along
with alcohol abuse, is among the leading causes of acute liver failure in the
US, Canada, UK and Australia. And almost half of the hospitalisations and
deaths associated with the painkiller are from accidental overdoses.
In India, where few
people are vaccinated against the liver-damaging Hepatitis A and B (infections
that spread through contaminated blood), food and water are the biggest cause
of liver damage, followed by alcohol abuse, liver cancer, haemochromatosis (a genetic
condition that leads to over-absorption of iron in the liver), and drug
toxicities, mostly paracetamol overdose.
HOW
MUCH IS TOO MUCH?
Paracetamol is widely
used to treat headaches and minor aches and pains from the common cold, viral
and bacterial infections, toothache, sprains, strains and menstrual cramps. It
is also a component of hundreds of widely used over-the-counter medicines and
syrups, including cold and cough medicines.
This often leads to
people unwittingly taking more than the safe daily dose, which is capped at
4,000 mg (eight tablets of 500 mg each). Selling the drug in smaller quantities
in blister packs, as in the UK and India, helps prevent overdose — intentional
and accidental — by making it difficult for a person in pain too many.
Toxicity occurs when the
drug builds up in the bloodstream faster than it can be cleared by the body. In
most people, small amounts of paracetamol are broken down into non-toxic forms
and secreted in the urine, but more than the maximum amount can cause the
built-up byproducts to disrupt liver function.
DRUG
TOXICITY
Though physicians are
supposed to voluntarily report adverse drug reactions to the Directorate
General of Health Services in India, this is rarely done.
Canada, with a population
of 35 million, reported 4,500 hospitalisations due to paracetamol overdose,
shows Health Canada data, which is asking for stricter labelling. The northern
Indian state of Uttar Pradesh, with a population of more than 200 million, has
reported none.
AM I AT
RISK?
There’s a very clear
threshold for what constitutes a safe dose, which has led to regulatory bodies
across the world, including in India, to recommend adults have no more than
4,000 mg a day. People with compromised livers — whether because of three or
more alcoholic (30 ml) drinks for men and two for women every day, or
undiagnosed liver infection or damage — should have it in doses lower than the
recommended limit. In children, taking slightly more than the therapeutic dose
over long periods can also cause toxicity. The symptoms of toxicity depend on
how much paracetamol is in your blood. More than 50% of people with underlying
liver disease have no symptoms, with signs of damage often showing up in
late-stage liver disease. It usually begins with vomiting and stomach ache and
progresses to jaundice (yellowing of the whites of the eyes and of the skin due
to high levels of bilirubin, a yellow pigment found in bile), dark urine, pale
or light-coloured stool, mental confusion, and retention of fluids in the abdomen
or belly. Untreated, this can lead to liver failure and death.
SECOND
CHANCES
On the upside, the liver
is the only human organ that regenerates, which can help reverse damage by
replacing scar tissue with new cells.
After infections — such
as the food- and water-borne Hepatitis E that causes sporadic jaundice
outbreaks in India — the liver can completely repair itself within a month, if
there are no complications.
Complications occur when
the regeneration is either incomplete, prevented by progressive development of
scar tissue within the liver, or if the damage is sudden, in which more than
50% of the liver cells have been killed over three to four days.
This usually happens with paracetamol overdose. In this
situation, the damaging agent such as a virus, medicine or alcohol continues
its attack on the liver and scars the tissue, which cannot be healed. This
causes cirrhosis, which is a late-stage disease that kills if the person
doesn’t get a liver transplant.
sanChita sharma
HT19SEP16
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