NCLEX-RN - Pharmacology & Medication Administration

The '5 Rights' are fundamental principles for safe medication administration:
1. Right Patient: Verify patient identity using at least two identifiers.
2. Right Drug: Ensure the correct medication is being administered.
3. Right Dose: Administer the prescribed amount of medication.
4. Right Route: Use the correct pathway for medication delivery (e.g., PO, IV, IM, SubQ).
5. Right Time: Administer medication at the scheduled time, considering appropriate intervals.

The Therapeutic Index (TI) is a measure of a drug's safety, representing the ratio between the toxic dose and the therapeutic dose. A high TI indicates a wide margin of safety (e.g., penicillin), while a low TI suggests a narrow margin of safety, requiring careful monitoring (e.g., warfarin, digoxin, lithium).

Drug Half-Life ($t_{1/2}$) is the time it takes for the concentration of a drug in the body to be reduced by 50%. It determines the dosing interval and the time it takes for a drug to reach steady state or be eliminated from the body. Generally, it takes about 4-5 half-lives for a drug to be almost completely eliminated.

An Adverse Drug Reaction (ADR) is any noxious, unintended, and undesired effect of a drug that occurs at doses used in humans for prophylaxis, diagnosis, or therapy. ADRs can range from mild (e.g., nausea) to severe (e.g., anaphylaxis, organ damage).

An idiosyncratic reaction is an unpredictable, abnormal, or peculiar response to a drug that is not an allergic reaction and does not occur in most patients. It is often genetically determined and can be severe, even with normal doses (e.g., G6PD deficiency leading to hemolytic anemia with certain drugs).

ACE Inhibitors block the enzyme Angiotensin-Converting Enzyme (ACE), preventing the conversion of Angiotensin I to Angiotensin II. This leads to vasodilation, decreased aldosterone secretion (reducing sodium and water retention), and decreased bradykinin breakdown, resulting in lower blood pressure. Common side effects include a dry cough and hyperkalemia.

Beta-Blockers selectively or non-selectively block beta-adrenergic receptors in the heart, lungs, and other tissues. This reduces heart rate, myocardial contractility, and cardiac output, leading to decreased blood pressure. They also reduce renin release from the kidneys. Side effects can include bradycardia, bronchospasm (non-selective), and fatigue.

Calcium Channel Blockers inhibit the influx of calcium ions into vascular smooth muscle cells and cardiac muscle cells. This causes vasodilation (reducing peripheral vascular resistance) and decreases myocardial contractility and heart rate (especially non-dihydropyridines like diltiazem/verapamil), leading to lower blood pressure and reduced cardiac workload. Side effects include peripheral edema, headache, and bradycardia.