SIDE EFFECTS OF PARACETAMOL Infusion:
NAUSEA, ALLERGIC REACTIONS, SKIN RASHES, ACUTE RENAL TUBULAR NECROSIS. POTENTIALLY FATAL: VERY RARE, BLOOD DYSCRASIAS (E.G. THROMBOCYTOPENIA, LEUCOPENIA, NEUTROPENIA, AGRANULOCYTOSIS); LIVER DAMAGE.
DRUG INTERACTIONS OF PARACETAMOL Infusion:
REDUCED ABSORPTION OF CHOLESTYRAMINE WITHIN 1 HR OF ADMIN. ACCELERATED ABSORPTION WITH METOCLOPRAMIDE. DECREASED EFFECT WITH BARBITURATES, CARBAMAZEPINE, HYDANTOINS, RIFAMPICIN AND SULFINPYRAZONE. PARACETAMOL MAY INCREASE EFFECT OF WARFARIN. POTENTIALLY FATAL: PARACETAMOL INCREASES THE RISK OF LIVER DAMAGE IN CHRONIC ALCOHOLICS. INCREASED RISK OF TOXICITY WITH OTHER HEPATOTOXIC DRUGS OR DRUGS WHICH INDUCE MICROSOMAL ENZYMES E.G. BARBITURATES, CARBAMAZEPINE, HYDANTOINS, RIFAMPICIN AND SULFINPYRAZONE.
PARACETAMOL EXHIBITS ANALGESIC ACTION BY PERIPHERAL BLOCKAGE OF PAIN IMPULSE GENERATION. IT PRODUCES ANTIPYRESIS BY INHIBITING THE HYPOTHALAMIC HEAT-REGULATING CENTRE. ITS WEAK ANTI-INFLAMMATORY ACTIVITY IS RELATED TO INHIBITION OF PROSTAGLANDIN SYNTHESIS IN THE CNS. ONSET: <1 HR. DURATION: 4-6 HR. ABSORPTION: INCOMPLETE; DEPENDS UPON DOSAGE FORM. TIME TO PEAK, SERUM: ORAL: 10-60 MIN; MAY BE DELAYED IN ACUTE OVERDOSES. DECREASED RATE OF ABSORPTION WITH FOOD. DISTRIBUTION: PRESENT IN MOST BODY TISSUES; CROSSES THE PLACENTA AND ENTERS THE BREAST MILK. PROTEIN BINDING: 8-43% (AT TOXIC DOSES). METABOLISM: HEPATIC VIA GLUCURONIC AND SULPHURIC ACID CONJUGATION. AT NORMAL THERAPEUTIC LEVELS, GLUCURONIDE METABOLITES ARE METABOLISED TO REACTIVE INTERMEDIATE (ACETYLIMIDOQUINONE) WHICH IS CONJUGATED WITH GLUTATHIONE AND INACTIVATED; AT TOXIC DOSES, GLUTATHIONE CONJUGATION IS INSUFFICIENT LEADING TO INCREASED ACETYLIMIDOQUINONE WHICH MAY CAUSE HEPATIC CELL NECROSIS. EXCRETION: PLASMA HALF-LIFE: 2.7 HR (ADULTS); 1.5-2 HR (INFANTS AND CHILDREN); 3.5 HR (NEONATES). NEONATES, INFANTS AND CHILDREN UP ≤10 YR EXCRETE LESS GLUCURONIDE THAN ADULTS. HALF-LIFE MAY BE LONGER AFTER TOXIC DOSES. EXCRETED MAINLY VIA URINE (2- 5% UNCHANGED; 55% AS GLUCURONIDE METABOLITES). TOTAL BODY CLEARANCE: 18 L/HR.