Case Study Aspirin Overdose.docx

**Case Study: Aspirin Overdose** **Answer Key** **1. Since aspirin is an acidic drug, where in the GI tract would you expect absorption to begin?** - **Answer:** - Aspirin absorption begins in the stomach. - **Rationale:** - Aspirin (acetylsalicylic acid) is a weak acid. Weak acids are...

**Case Study: Aspirin Overdose** **Answer Key** **1. Since aspirin is an acidic drug, where in the GI tract would you expect absorption to begin?** - **Answer:** - Aspirin absorption begins in the stomach. - **Rationale:** - Aspirin (acetylsalicylic acid) is a weak acid. Weak acids are absorbed more readily in acidic environments, like the stomach, where the pH is low. The non-ionized (lipid-soluble) form of aspirin is more likely to cross the stomach lining into the bloodstream, making the stomach the primary site of absorption for this drug. **2. Would you expect the results of pumping the stomach to be as useful for aspirin ingestion as it would for ingestion of a basic drug such as codeine?** - **Answer:** - No, stomach pumping (gastric lavage) may be less effective for aspirin ingestion compared to basic drugs like codeine. - **Rationale:** - Aspirin is absorbed quickly in the stomach, so by the time the patient is brought to the emergency room, a significant portion of the drug may already be absorbed into the bloodstream. This makes gastric lavage less effective. In contrast, basic drugs like codeine are less readily absorbed in the acidic environment of the stomach and remain in the stomach longer, making gastric lavage more useful. **3. At a urinary pH of 6.0, in what form are the majority of salicylate molecules?** - **Answer:** - Non-ionized (lipid-soluble) form. - **Rationale:** - At a urinary pH of 6.0 (which is slightly acidic), salicylate molecules, which are weak acids, are largely non-ionized. In this form, they are more likely to be reabsorbed from the kidney tubules back into the bloodstream, prolonging their presence in the body and increasing the risk of toxicity. **4. At a urinary pH of 8.0, in what form are the majority of salicylate molecules?** - **Answer:** - Ionized (water-soluble) form. - **Rationale:** - At a urinary pH of 8.0 (alkaline), salicylate molecules become ionized. Ionized (water-soluble) molecules are less likely to be reabsorbed in the kidney tubules and are more likely to be excreted in the urine. This is important in treating aspirin overdose, as it facilitates the removal of the drug from the body. **5. In the non-ionized form, what happens to the salicylate molecules in the tubular filtrate?** - **Answer:** - They are reabsorbed into the bloodstream. - **Rationale:** - Non-ionized (lipid-soluble) molecules, like salicylate in an acidic environment, can pass through the lipid membranes of the kidney tubules and be reabsorbed back into circulation. This reabsorption prolongs the drug's effects and contributes to potential toxicity. **6. What action will sodium bicarbonate have on the pH of the tubular filtrate?** - **Answer:** - Sodium bicarbonate will increase the pH of the tubular filtrate, making it more alkaline. - **Rationale:** - Sodium bicarbonate, when administered, raises the pH of the blood and urine, making the environment more alkaline. This promotes the ionization of acidic drugs like aspirin, which then prevents reabsorption in the kidney tubules and enhances excretion. **7. What is the effect of administering sodium bicarbonate to Marcia?** - **Answer:** - Administering sodium bicarbonate will help increase the excretion of aspirin by alkalinizing the urine and preventing reabsorption of the drug. - **Rationale:** - Sodium bicarbonate increases urinary pH, causing aspirin (a weak acid) to become ionized and water-soluble. In this ionized form, aspirin is trapped in the renal tubules and is excreted more effectively in the urine. This process, known as \"ion trapping,\" helps reduce the circulating levels of aspirin and minimizes the risk of toxicity. **Key Concepts:** **Aspirin Absorption:** - Aspirin is absorbed in the stomach, as it is a weak acid. Drugs that are weak acids tend to be absorbed in acidic environments like the stomach, while weak bases are better absorbed in more basic environments, like the small intestine. **Drug Ionization and Reabsorption:** - The ionization of drugs in the kidneys affects whether they are reabsorbed or excreted. Non-ionized drugs are reabsorbed, while ionized drugs are excreted. This is important in overdose cases because altering the pH of urine can increase excretion of a toxic substance. **Alkalinization of Urine:** - Administering sodium bicarbonate in cases of aspirin overdose is a common treatment because it raises the pH of the urine, causing the acidic drug to become ionized and more easily excreted, reducing the risk of further toxicity. **Importance of Organ Function:** - The efficiency of drug metabolism and excretion depends heavily on kidney and liver function. Impairment of either organ can lead to prolonged drug action and increased risk of toxicity, which is crucial to monitor in pediatric cases where overdose is a concern.