Adverse Drug Reactions
|
Paracetamol: Nausea, allergic reactions, skin rashes, acute renal tubular necrosis. Aceclofenac: Diarrhoea, headache,
vertigo, dizzies, nervousness, tinnitus, depression, drowsiness, insomnia; fever, angioedema, bronchospasm, rashes; blood
dyscrasias.
Potentially Fatal:
Paracetamol: Very rare, blood dyscrasias (eg, thrombocytopaenia, leucopaenia, neutropaenia, agranulocytosis); liver damage.
Aceclofenac: Severe GI bleeding; nephrotoxicity.
|
Drug Interactions
|
Paracetamol: Reduced absorption of cholestyramine within 1 hr of administration. Accelerated absorption with
metoclopramide. Aceclofenac: M0ay increase the plasma concentrations of lithium and digoxin. Increased nephrotoxicity with
diuretics. Serum-potassium should be monitored when used with potassium-sparing diuretics. May enhance activity of
anticoagulants. May increase plasma methotrexate levels leading to toxicity if administered within 2-4 hr of methotrexate
admin. Risk of convulsions with quinolones.
Potentially Fatal:
Paracetamol: Increased risk of liver damage in chronic alcoholics. Increased risk of toxicity with high doses or long term
admin of barbiturates, carbamazepine, hydantoins, isoniazid, rifampin and sulfinpyrazone.
|
Mechanism of Action
|
Aceclofenac is a phenylacetic acid derivative that inhibits synthesis of the inflammatory cytokines interleukin-1b and
tumour necrosis factor, and inhibits prostaglandin E2 production. It increases glycosaminoglycans (GAG) synthesis, the
principal macromolecule of the extracellular matrix, which aids in repair and regeneration of articular cartilage. Thus,
aceclofenac has +ve effects on cartilage anabolism combined with modulating effect of matrix catabolism. Paracetamol has
analgesic and antipyretic action with weak anti-inflammatory activity. It produces analgesia by increasing pain threshold
and antipyresis by acting on the hypothalamic heat-regulating centre.
Absorption:
Aceclofenac: Rapidly absorbed; almost 100% bioavailability; peak plasma levels reached about 1.25-3 hr after oral admin.
Distribution:
Aceclofenac: >99.7% bound to plasma proteins; distributes into synovial fluid. Paracetamol: Distributes throughout most
fluids of the body.
Metabolism:
Aceclofenac: Probably metabolised by CYP2C9; average plasma elimination half-life: 4-4.3 hr. Paracetamol: Mainly
metabolised hepatically; plasma elimination half-life: 1-4 hr.
Excretion:
Aceclofenac: About two-thirds of the administered dose is removed in the urine, mainly as conjugated hydroxymetabolites.
Paracetamol: Most metabolites are removed in the urine within 24 hr.
|