Assessment of the severity and causes of pain dictate the type of drugs used for treatment. The choice of drugs and route of administration is dependent on

1. The severity of the pain.

2. The frequency and duration of the pain.

3. The source or cause of the pain.

Drugs used to treat pain can be broadly divided into analgesics and adjuvant drugs. Adjuvant drugs are not considered analgesics (per se), however, they can augment the analgesic properties of analgesics for specific pain syndromes, for instance corticosteroids for spinal cord compression or antidepressants for neuropathic pain. In addition, adjuvant drugs include those which can be used to manage undesirable but expected adverse effects of analgesics.

The goal of pain management is to achieve the best possible pain relief with the least side effects. Choices of drugs, doses, and routes should be tailored to meet these goals for the individual patient.

The WHO three-step ladder is useful for establishing the class of drug to start with depending on the severity of the pain at initial assessment, or if there is a failure to achieve adequate pain control with less potent drugs.

Step 1. Analgesics for mild pain include aspirin, acetaminophen and NSAIDs. These drugs have a ceiling effect (beyond a certain dose range, increasing the dose does not provide for greater analgesic effect), and have specific organ toxicities at high doses. Acetaminophen is the only drug in this group which has no antiplatelet activity, which may be important postsurgery and in patients with thrombocytopenia or thrombopathy.