P1: PCX Printer: Yet To Come
9780521704632c09 CUFX213A/Peck 9780521618168 December 28, 2007 11:33
Section IICoredrugs in anaesthetic practiceTreatment
Activated charcoal
Intravenous glucose
Acetylcysteine or methionine
Early referral to specialist centreAcetic acid derivatives
Diclofenac
Diclofenac is a phenylacetic acid derivative.Presentation
Diclofenac is available in a parenteral as well as an oral and rectal formulation.
The intravenous preparation should be diluted and administered over a minimum
of 30 minutes. It is also available in combination with misoprostil, which provides
prophylaxis against gastric and duodenal ulceration. The maximum adult dose is
150 mg.day−^1 in divided doses. The paediatric dose is 1 mg.kg−^1 tds for pain associ-
ated with minor surgery (tonsillectomy, inguinal herniotomy).Uses
Diclofenac may be used alone to treat mild to moderate post-operative pain or to
reduce opioid consumption when treating severe pain. It is particularly useful in
treating renal colic. Owing to its effects on cyclo-oxygenase it may also precipitate
gastric irritation, acute renal impairment and reduced platelet function, which often
prevents it from being used in major surgery.Other effects
Gut–diclofenac produces less gastric irritation than both indomethacin and
aspirin.
Pain – the parenteral formulation is highly irritant and intramuscular injection
may be very painful and is associated with muscle damage. Intravenous injection
causes local thrombosis.
Interactions – plasma concentrations of lithium and digoxin may be increased. In
general it does not effect either oral anticoagulants or oral hypoglycaemic agents,
but isolated reports would suggest that close monitoring is used.Kinetics
Inkeeping with other drugs in its class diclofenac is well absorbed from the
gut, highly plasma protein bound (99%) and has a small volume of distribution
(0.15 l.kg−^1 ). It undergoes hepatic hydroxylation and conjugation to inactive
metabolites that are excreted in the urine (60%) and bile (40%).