Comparative pharmacology of 'non-opioid' analgesics

Abstract

Pain is the most prominent symptom of disease in man and analgesics are the most widely used drugs. More than 90% of the analgesics used belong to the so-called peripherally acting, non-opioid (non-narcotic) or mild analgesics. They all derive from 3 types of compounds: aspirin and other acidic non-steroidal anti-inflammatory drugs (NSAIDs), aniline derivatives such as paracetamol (acetaminophen) and non-acidic pyrazole drugs like propyphenazone and dipyrone (metamizole). These compounds and all of their derivatives differ in their analgesic activity and their typical profile of side effects. While NSAIDs are particularly useful in the treatment of pain related to inflammation these compounds are well known to cause gastrointestinal, haematological and kidney side effects. Aniline derivatives such as paracetamol are not very effective analgesics, but reasonably good antipyretics. These compounds, unlike aspirin-like drugs, do not interfere with inflammatory pain. Their main side effects are allergic but, particularly at overdose, they cause liver and kidney damage. Rarely, they have also been associated with kidney damage and malignomas of the urinary system after long term administration. Non-acidic pyrazole drugs are supposedly particularly active in pain originating from spasms of smooth muscles. They are not very effective anti-inflammatory drugs but are good antipyretics. Their major side effects consist of mild allergic reactions. They have also rarely been associated with agranulocytosis and shock. In addition to these differences in therapeutic application and side effect profile the major representatives of the groups of analgesics mentioned differ in their pharmacokinetic behaviour in the human body. Aspirin shows non-linear pharmacokinetics not seen with ibuprofen, a more modern NSAID.(ABSTRACT TRUNCATED AT 250 WORDS)