Renal and GI Function Quiz

Housekeeping Functions and Cytoprotective PGs

• Renal blood flow, GI function, mucosal proliferation, and platelet function are regulated by the housekeeping function.
• Prostaglandins (PGs) in the GI tract provide cytoprotection.

COX Enzyme Functions

• COX-2 is induced during inflammation and is essential for renal development and brain function.
• COX-2 mediates vascular production of prostacyclin, which causes vasodilation.
• COX-1 is constitutive in gastric cells, producing PGs that protect epithelial and parietal cells.

Smooth Muscle Responses

• Vascular actions: Thromboxane A2 (TXA2) induces vasoconstriction while PGE2 and PGI2 act as vasodilators.
• Airways: PGE2 and PGI2 relax smooth muscle, whereas TXA2 and PGF2α cause contraction. Leukotrienes (LTs) also contribute to contraction.

Asthma and NSAID Effects

• In asthma, NSAIDs (like aspirin) can provoke bronchospasm and dyspnea due to excess production of cysteinyl leukotrienes.

Gastrointestinal Considerations

• NSAIDs frequently cause gastrointestinal distress, bleeding, and gastritis due to inhibited acid production and altered mucus/bicarb secretion.
• COX-2 and acetaminophen (Tylenol) generally have fewer GI side effects.

Platelet Function and Thrombotic Risks

• COX-2 in endothelial cells produces PGI2, which inhibits platelet aggregation; inhibiting COX-2 may increase clotting risks.
• COX-1 stimulates TXA2, increasing clotting risk in myocardial infarction; low-dose aspirin effectively blocks TXA2.

FDA Warnings for NSAIDs

• Non-aspirin NSAIDs can elevate the risk of heart attacks or strokes by 10-50%, necessitating updated warnings, particularly at high doses and extended durations.

Kidney Function and NSAIDs

• COX inhibitors can impair renal function, worsen hypertension, and exacerbate congestive heart failure.

Uterine Function of Prostaglandins

• Prostaglandins stimulate uterine contractions and can induce labor; NSAIDs may prolong labor.
• They maintain patent ductus arteriosus in utero; NSAIDs can cause premature closure if administered late in pregnancy but assist in ductus closure post-premature birth.

Nervous System Effects of Prostaglandins

• PGE1 and PGE2 raise body temperature via hypothalamic action.
• PGEs inhibit norepinephrine release, potentially leading to increased vasoconstriction when NSAIDs are used.
• PGE2 can cause hyperalgesia at inflammation sites, with NSAIDs providing acute relief.

General Characteristics of NSAIDs

• Organic acids (except Nabumetone) accumulate in inflamed tissues.
• Most NSAIDs have reversible effects, with aspirin having a unique long-lasting effect.

Shared Therapeutic Effects of NSAIDs

• NSAIDs are utilized for inflammation reduction (acetaminophen is an exception), antipyretic effects, and analgesia.
• Aspirin is contraindicated in children for viral-induced fever due to the risk of Reye's syndrome; acetaminophen is preferred.

Ibuprofen (Motrin)

• Typical dosing is 400 mg every 4-6 hours, adjustable up to 3200 mg per day.
• Recommended to be taken with food to mitigate GI side effects; half-life is about 2 hours.
• Newly approved IV formulation for patients unable to tolerate oral medications.

Naproxen (Aleve)

• Fully absorbed with a peak effect in 2-4 hours; half-life is 14 hours.
• Elderly patients require dosage adjustments due to increased serum concentrations.
• Associated with a heightened risk of cardiovascular events, warranting FDA warnings.

Ketorolac (Toradol)

• Potent analgesic, effective for postoperative pain, used for short-term pain relief, not for chronic management.
• Increased potency corresponds to greater risk of adverse effects on the GI tract and renal function.

COX-2 Selective Agents

• These agents specifically inhibit COX-2, providing anti-inflammatory, analgesic, and antipyretic effects with fewer GI complications.
• Celecoxib (Celebrex) is more selective for COX-2, showing efficacy comparable to traditional NSAIDs, without prothrombotic effects at therapeutic doses.

Acetaminophen (Tylenol)

• Used as an alternative to aspirin for analgesia and fever reduction; raises pain thresholds and affects hypothalamic function for antipyretic action.
• Lacks peripheral COX inhibition, showing no anti-inflammatory effects and little impact on platelets or uric acid levels.

Test your understanding of renal and gastrointestinal housekeeping functions, including blood flow and mucosal proliferation. This quiz covers the roles of prostaglandins and their effects on vascular smooth muscle and airways, especially in the context of inflammation and asthma.