Paracetamol.... our best known "unknown"

Paracetamol

Perhaps the most familiar medicinal substance to all of us after aspirin.

It is a medicine that exists in every home and is used by young and old.

But how much do we know about its action and its correct use?

Paracetamol, also known as acetaminophen, is a mild inhibitor of prostaglandin synthesis and as such has an antipyretic, analgesic and mild anti-inflammatory effect.

It exerts its action mainly by acting centrally (cerebral) since it activates the descending analgesic pathways of the brain to the spinal cord (these pathways block the pain transmission signal to the spinal cord).

Where does the circuit of descending analgesia begin?
Descending analgesic pathway from the midbrain through the brainstem to the spinal cord. Neurons that secrete enkephalin inhibit the transmission of incoming pain fibers to the spinal cord.

It also has an effect on neuropathic pain.

PARACETAMOL DOSAGE

The maximum dose for adults and children over 12 years of age is 4 grams per day, i.e. up to 4 Depon Maximum effervescent tablets per day or 8 Depon 500mg tablets per day.

Children 6-12 years: 250-500mg 3-4 times a day.

Children 1-5 years: 125-250mg 3-4 times a day.

In children under 12 years of age, the maximum daily dose of paracetamol is 60mg/kg per day in 3 or 4 divided doses, approximately 10-15mg/kg every 6 hours.

Paracetamol (acetaminophen) toxicity

The toxic dose of paracetamol is highly variable. Doses higher than 4 grams lead to an increased risk of toxicity. In adults, single doses above 10 grams or 200 mg/kg body weight have a reasonable chance of causing toxicity.

Be careful when co-administering preparations that already contain paracetamol together with another medicinal substance, such as the strong muscle relaxant-painkiller Norgesic. In such cases, we are very careful about the dose of paracetamol we consume. We reduce our dose by 1-2 Depon/Panadol/Apotel tablets to avoid toxicity.

Similarly we do the same when we are given preparations containing codeine and paracetamol together, such as Zaldiar.

Pharmacist

Zachos Evangelos - King's College London (Master Of Pharmacy)