ACETAMINOPHEN (PARACETAMOL)

 ACETAMINOPHEN (PARACETAMOL)

BRAND NAME:-CROCIN 500,1000mg tabs; METACIN,PARACIN 500mg tab, 125mg/5ml syrup,150mg/ml paed. Drops,ULTRAGIN, PYRIGESIC ,CALPOL 500mg tab,125mg tab,125mg/5ml syrup,

Paracetamol rectal suppository 80,170mg. And other many brands available in India.

PARACETAMOL (acetaminophen) is a para-amino  phenol derivatives, analgesic, good antipyretic and weak anti-inflammatory action. 

MECHANISM OF ACTIONS:- 

The central analgesic action of Paracetamol is like aspirin,i.e. it raises pain threshold,but has weak peripheral anti-inflammatory components. Analgesic action of aspirin and Paracetamol is additive. Paracetamol is a good and promptly acting antipyretic.

It is a poor inhibitor of PG synthesis in peripheral tissues,but more active on COX in the brain. One explanation offered for the discrepancy between it's analgesic -antipyretic and anti-inflammatory action is its inability to inhibit COX in the presence of peroxide which are generated at sites of inflammation,but are not present in brain. The ability of acetaminophen to inhibit COX-3 (AN ISOENZYME SO FAR LOCATED IN DOG BRAIN) could also account for its analgesic antipyretic action.

In contrast to aspirin, acetaminophen does not stimulate respiration or affect acid-base balance; does not increase cellular metabolism. It has no effect on CVS. Gastric irritation is insignificant — mucosal erosion and bleeding occur rarely only in overdose. It does not affect platelet function or clotting factors and is not uricosuric.

PHARMACOKINETICS:-

Acetaminophen is well absorbed orally, only about 1/4th is protein bound in plasma and it is uniformly distributed in the body. Metabolism occurs mainly by conjugation with glucuronic acid and sulfate : conjugated are excerted rapidly in urine. Plasma t½ is 2-3 hours . Effects after an oral dose last for 3-5 hours.

USE:-

Paracetamol is one of the most commonly used 'over-the-counter' analgesic for headache,mild migraine, musculoskeletal pain,dymenorhoea , paracetamol poisoning etc.

DOSE:- 325-650mg (children 10-15mg/kg)3-5 times a day.

SIDE EFFECTS:-  IN isolated antipyretic doses Paracetamol is safe and well tolerated. Nausea and rashes occurs occasionally, leucopenia is rare. 

NOTE:- THE DCGI HAS ALLOWED TO MANUFACTURERS A PERIOD OF 3 YEARS TO LIMITED THE TOTAL AMOUNT OF PARACETAMOL PER TAB./ CAP.(SINGLE DRUG OR COMBINED FORMULATION) TO 325MG.