paracetamol

Paracetamol — called acetaminophen in the United States — is the gentle, almost universal painkiller and fever reducer found in nearly every home. It eases mild to moderate pain and brings down fever, yet unlike the NSAIDs it has little anti-inflammatory action and does not irritate the stomach or thin the blood, which makes it a safe first choice for headaches, colds, and children's fevers.

Curiously, after more than a century of use its exact mechanism is still not fully settled. It appears to act mostly within the central nervous system rather than at sites of inflammation, where it reduces prostaglandin signaling, and it may also engage the body's own cannabinoid and serotonin pain-modulating systems. This central, non-inflammatory action explains why it relieves pain and fever but does little for the swelling of arthritis.

Paracetamol is extraordinarily safe at the correct dose and dangerously toxic just above it — an unusually narrow safety margin for a household drug. In overdose, the liver's normal detoxifying capacity is overwhelmed and a reactive metabolite (NAPQI) destroys liver cells, causing fatal liver failure days later. The antidote, acetylcysteine, replenishes the protective molecule (glutathione) that mops up the toxic metabolite, and it works best when given early. This is why staying within the daily limit matters so much, especially since paracetamol is hidden inside many combination cold and pain products.