McKenna's Pharmacology for Nursing, 2e

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P A R T 3  Drugs acting on the immune system

TABLE 16.1

DRUGS IN FOCUS Salicylates

Drug name

Dosage/route

Usual indications

aspirin (Aspro, Astrix)

Adult: 325–650 mg PO or PR q 4 hours Myocardial infarction (MI): 300–325 mg PO Paediatric: 65–100 mg/kg per day PO or PR in four to six divided doses; if <2 years of age, consult with prescriber Three 750-mg capsules PO t.d.s. for 8 weeks

Treatment of fever, pain, inflammatory conditions; at low dose to prevent the risk of death and MI in people with history of MI, prevention of transient ischaemic attacks Treatment of mildly to moderately acute ulcerative colitis in adults Treatment of ulcerative colitis and other inflammatory bowel diseases in adults Treatment of ulcerative colitis and other inflammatory bowel diseases in adults

balsalazide (Colazide)

mesalazine (Pentasa, Mesasal) olsalazine (Dipentum)

500 mg PO t.d.s.; one enema at bedtime, or one suppository once daily

1 g/day PO in two divided doses

Therapeutic actions and indications Salicylates inhibit the synthesis of prostaglandin, an important mediator of the inflammatory reaction (Figure 16.1). The antipyretic effect of salicylates may be related to blocking of a prostaglandin mediator of pyrogens (chemicals that cause an increase in body tem- perature and that are released by active white blood cells) at the thermoregulatory centre of the hypothalamus. At low levels, aspirin also affects platelet aggregation by inhibiting the synthesis of thromboxane A 2 , a potent vasoconstrictor that normally increases platelet aggrega- tion and blood clot formation. At higher levels, aspirin inhibits the synthesis of prostacyclin, a vasodilator that inhibits platelet aggregation. Salicylates are indicated for the treatment of mild to moderate pain, fever and numerous inflammatory condi- tions, including rheumatoid arthritis and osteoarthritis. (See Box 16.3 and the Critical thinking scenario for more on rheumatoid arthritis.) See Table 16.1 for usual indications for each type of salicylate. Pharmacokinetics Salicylates are readily absorbed directly from the stomach, reaching peak levels within 5 to 30 minutes. They are metabolised in the liver to salicylic acid, an active metabolite and excreted in the urine, with a half-life of 15 minutes to 12 hours, depending on the salicylate. Salicylates cross the placenta and enter breast milk; they are not indicated for use during pregnancy or breastfeeding because of the potential adverse effects on the neonate and associated bleeding risks for the mother. Contraindications and cautions Salicylates are contraindicated in the presence of known allergy to salicylates, other NSAIDs (more common with a history of nasal polyps, asthma or chronic urticaria) or tartrazine (a dye that has a cross-sensitivity with aspirin) because of the risk of allergic reaction ; allergic reaction to aspirin can induce bronchospasm and, in rare cases,

Salicylates are some of the oldest anti-inflammatory drugs used. They were extracted from willow bark, poplar trees and other plants by ancient peoples to treat fever, pain and what we now call inflammation. They are generally available without prescription and are relatively non-toxic when used as directed. Aspirin ( Aspro , Astrix , Cartia , Cardiprin and others), which is available OTC, is one of the most widely used drugs for treating inflammatory conditions. Additional synthetic salicylates include balsalazide ( Colazide ), mesalazine ( Pentasa, Mesasal ) and olsalazine ( Dipentum ) which are mostly used to reduce inflammation in ulcerative colitis and other inflammatory bowel diseases. A person who does not respond to one salicylate may respond to a dif- ferent one. Sensitivity to anti-inflammatory drugs African Americans have a documented decreased sensitivity to the pain-relieving effects of many of the anti-inflammatory drugs.They do, however, have an increased risk of developing GI adverse effects to these drugs, including paracetamol.This should be taken into consideration when using these drugs as analgesics. Increased doses may be needed to achieve a pain- blocking effect, but the increased dose will put these people at an even greater risk for development of the adverse GI effects associated with these drugs. Monitor these people closely, and use non-drug measures to decrease pain, such as positioning, environmental control, physiotherapy, warm soaks and so on. If African American people are prescribed anti-inflammatory drugs, provide teaching about the signs and symptoms of GI bleeding and what to report, and monitor regularly for any adverse reactions to these drugs. Sensitivity to anti-inflammatory drugs has been reported in other ethnic groups such as Japanese, Koreans and Chinese. However, evidence is still inconclusive and more multicentre research in the future is needed to establish pharmacogenetic considerations in prescribing NSAIDs in some ethnic populations. Cultural considerations BOX 16.2