Chapter 116: Nonsteroidal Anti-Inflammatory Drugs

HIGH-YIELD FACTS

Nonsteroidal anti-Inflammatory drugs (NSAIDs) have analgesic, antipyretic, and anti-inflammatory effects and are among the most commonly used drugs in the world. While acute therapeutic use is regarded as safe in most patients, adverse reactions at therapeutic doses and with chronic use has resulted in a reevaluation of its safety in recent years. The introduction and subsequent withdrawal of cyclooxygenase (COX)-2-selective agents have resulted a decrease in the use of these agents. Ibuprofen and naproxen are currently the only nonprescription NSAIDs available in the United States. They are also available in combination cough and cold preparations as well as the prescription combination drug, Vicoprofen (ibuprofen and hydrocodone). Other prescription forms of NSAIDs are also available in the United States and globally.

Due to its nonprescription status and wide use, unintentional and intentional ingestions are common. The 2015 Annual Report of the American Association of Poison Control Centers listed 58 deaths in which NSAIDs were a contributing factor, with 11 deaths related to a single substance (ibuprofen, ibuprofen/diphenhydramine combination product, and colchicine). NSAIDs accounted for more than 76,000 single exposures, of which more than 61,000 were attributed to ibuprofen. As expected, children younger than 6 years had the majority of exposures, with over 41,000 single exposures to NSAIDs.¹ In addition, unintentional ibuprofen exposures resulted in 16% of visits for over-the-counter liquid medication exposures in young children.² Symptoms in the overdose setting are rare; however, severe toxicity can occur.

PHARMACOLOGY

NSAIDs have numerous classifications including their COX activity, biochemical properties, and pharmacologic action that have been well documented³ (Table 116-1). They are similar in their biochemical characteristics in that they are relatively lipophilic, weak acids. While most are absorbed readily from the gastrointestinal tract, their pharmacokinetic properties differ. Thus the clinician can select for specific indications. The duration of action and half-life guides dosing with short half-life NSAIDs (e.g., ibuprofen) administered every 6 to 8 hours and longer half-life NSAIDs (e.g., naproxen) dosed once or twice daily. Metabolism and elimination are important pharmacokinetic properties to consider when dosing NSAIDs. Polymorphisms in the drug metabolizing enzyme cytochrome P450 2C9 (CYP2C9) can affect pharmacokinetics.⁴ Specifically, those individuals with the *2 and/or *3 alleles (nonfunctioning alleles) are predisposed to higher risks of adverse drug reactions.⁵ In addition, adverse reactions are likely to occur with hepatic and renal disorders. Drug interactions can result in adverse effects when taking into account metabolism and other substrates that can affect enzyme function.