Analgesic options
The World Health Organization introduced the concept of the 'analgesic ladder in which paracetamol with or without non- steroidal anti-inflammatory drugs (NSAIDs) were used first. then weaker opioids such as codeine and, then finally. strong opioids such as morphine are used. This model works well for conditions where the intensity of pain increases over time, but is inappropriate in acute pain where the intensity is expected to decrease in a relatively short time. The inverse of this approach should be used where a number of different drugs are used in the early stages with the more potent drugs (which usually have more side-effects) being tapered and discontinued as the pain intensity falls.
Analgesics fall into three main categories: paracetamol. the NSAIDs and cyclo-oxygenase (cox) 2 inhibitors ('Coxibs) that share a similar mode of action. and the opioids. The term opioid is used as an inclusive term incorporating not only the naturally occurring opiates (for example morphine) and synthetic opioids (for example fentanyl), but also endogenous opioids such as the endomorphins. It is logical to combine drugs that act via different mechanisms to try to maximize pain control with a minimum of side-effects a concept known as multi-model analgesia. Some combinations, such as tramadol and paracetamol. exhibit synergy. that is where the effect is greater than the sum of the effects of the two drugs when used individually. Analgesic efficacy can be expressed as the number needed to treat" (NNT). Calculation of the NNT of a treatment involves assessing the number of patients who achieve a specific thera- peutic target whilst allowing for those patients who received placebo who also reached that target. For analgesics used to treat acute pain, the target is usually the ability to reduce the pain by 50% or greater. It is notable that intramuscular morphine 10 mg has a higher NNT (that is lower efficacy) than a number of regularly used simple analgesics