Some of the views expressed in the following notes on newly approved products should be regarded as preliminary, as there may have been limited published data at the time of publication, and little experience in Australia of their safety or efficacy. However, the Editorial Executive Committee believes that comments made in good faith at an early stage may still be of value. Before new drugs are prescribed, the Committee believes it is important that more detailed information is obtained from the manufacturer's approved product information, a drug information centre or some other appropriate source.
Dynastat (Pharmacia Australia)
vials containing 20 mg and 40 mg powder for reconstitution
Approved indication: postoperative analgesia
Australian Medicines Handbook Section 15.1.1
Parecoxib is a non-steroidal anti-inflammatory drug. It is the prodrug of valdecoxib which reduces the production of inflammatory mediators by inhibiting the enzyme cyclo-oxygenase 2.
The plasma half-life of parecoxib is only 22 minutes because of its rapid conversion to valdecoxib. Analgesia begins within 15 minutes of an intravenous or intramuscular injection and reaches a peak in two hours. Valdecoxib is extensively metabolised and most of the metabolites are excreted in the urine. This metabolism includes cytochrome P450 3A4 and 2C9, so there is a potential for interaction with drugs which inhibit or induce these enzymes. Valdecoxib can also affect other liver enzymes. It may inhibit CYP2C19 and CYP2D6 creating the potential for more interactions.1
The analgesic effects of parecoxib have been studied in patients having dental, gynaecological or orthopaedic surgery. Parecoxib was more effective than placebo. Depending on the surgery, the duration of analgesia after a single dose was 6-12 hours. One study compared intramuscular and intravenous doses of parecoxib with placebo and intramuscular ketorolac in 304 patients having impacted wisdom teeth extracted. All the active treatments gave more pain relief than placebo and a 40 mg dose of parecoxib was significantly better than 20 mg. Ketorolac had a significant advantage over parecoxib in the first few hours after surgery, but parecoxib gave significantly more pain relief 16 and 24 hours after treatment.2
Parecoxib has only been approved for use as a single perioperative injection so most of the safety data refer to single doses. It can be difficult to separate the adverse reactions from the effects of the surgery, but some adverse events occurred more frequently with parecoxib than with placebo. These include dyspepsia, changes in blood pressure, oliguria, oedema and itching. Caution is needed if the patient has hypertension or impaired cardiac, renal or hepatic function. Parecoxib can cause gastric erosions and ulcers so patients with a history of peptic ulcer may be at risk.
Non-steroidal anti-inflammatory drugs do have a role in postoperative analgesia.3 For patients who cannot swallow, parecoxib is probably an alternative to ketorolac, but it has not yet been widely used.
