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disturbances limit their use. Newer COX-2-specific NSAIDs have the advantage that they have similar analgesia and anti-inflammatory effects (Reicin et al. 2001) but have no effect on platelets or the gastric mucosa (Rowbotham 2000). As a result, coagulation problems and gastrointestinal irritation are likely to be significantly reduced. However, recently several of these drugs have been withdrawn from the market due to long-term cardiovascular side-effects and it will take time for newer products with an improved safety profile to re-establish themselves in practice (Macintyre et al. 2010).

Opioid analgesics

Opioids are the first-line treatment for pain that follows major surgery (Macintyre and Jarvis 1996) and can also be prescribed for cancer and non-cancer related chronic pain. Opioid doses need to be titrated carefully to achieve pain relief to suit each individual patient while minimizing any unwanted side-effects (McQuay et al. 1997).

A number of opioids are used for controlling pain following surgery. These include morphine, diamorphine, fentanyl and oxycodone. The most common routes of opioid administration are intravenous, epidural, subcutaneous, intramuscular or oral.

Evidence for the concept of opioid rotation when patients have intolerable opioid-related side-effects originates from cancer pain studies (Quigley 2004) but it may be a useful strategy to consider in the management of acute pain as well.

Opioids for mild to moderate pain

Tramadol

Another opioid for mild to moderate pain, which has been shown to be an effective analgesic for postoperative pain, is tramadol (McQuay and Moore 1998, Reicin et al. 2001). Although tramadol does have some side-effects, which include nausea and dizziness, it is free of NSAID side-effects and causes less constipation than codeine preparations and opioids (Bamigbade and Langford 1998). The combination of tramadol with paracetamol is more effective than either of the two components administered alone (McQuay and Edwards 2003).

Codeine phosphate

Codeine is metabolized by the hepatic cytochrome CYP2D6 to morphine. Approximately 7% of Caucasians and 1–3% of the Asian population are poor CYP2D6 metabolizers and therefore do not experience effective analgesia with codeine.

Codeine is available in tablet and syrup formulations. Doses of 30–60 mg po qds are generally prescribed to a maximum of 240 mg/24 h. It is also available in combination preparations with a non-opioid. The combination preparations are available in varying strengths of codeine and paracetamol, including co-codamol 8 mg/500 mg, 15 mg/500 mg and 30 mg/500 mg.

Opioids for moderate to severe pain

Morphine

A large amount of information and research is available concerning morphine and therefore it tends to be the drug of choice within this category (Hanks et al. 2001, 2004). It is available in oral, rectal, parenteral and intraspinal preparations. A recent study of 43 European palliative care units showed that morphine was the most frequently used opioid for moderate to severe pain, with over 50% of patients taking oral or parenteral preparations (Klepstad et al. 2005).

All strong opioids require careful titration from an expert practitioner. It is better to begin with a small dose, usually one that is equivalent to the previous medication, and increase gradually in conjunction with careful assessment of its effectiveness (Hanks et al. 2001). Titration begins with the immediate-release form which is available in tablet (Sevredol) or elixir (Oramorph) preparations, and once pain control is achieved the patient can be converted to a modified-release preparation that acts over a 12- or 24-hour period (Zomorph or MXL respectively).

Breakthrough analgesia is administered using the equivalent 4-hourly dose of the immediate-release form. This dose can be given as required (hourly) and subsequent adjustments can be made to the modified form if the patient is requiring more than three breakthrough doses in a 24-hour period (Hanks et al. 2001).

Patients should be informed of potential side-effects such as constipation,