Pharmacology — Advanced — NCLEX-PN

Potassium is an electrolyte (normal 3.5–5.0 mEq/L) essential for cardiac and skeletal muscle function. IV potassium is never given by push — it must always be diluted and infused on a pump — because rapid IV potassium can cause fatal cardiac arrest; oral forms are taken with food to limit GI irritation. Both hypokalemia and hyperkalemia cause life-threatening arrhythmias, so the level is watched closely.

Lithium is a mood stabilizer for bipolar disorder with a narrow therapeutic range of 0.6–1.2 mEq/L. Because lithium and sodium are handled similarly by the kidneys, the client must keep sodium and fluid intake steady — low sodium or dehydration drives lithium toxicity. Early toxicity shows as tremor and GI upset, progressing to confusion, ataxia, and seizures, so levels are monitored regularly.

Metformin is the first-line oral biguanide for type 2 diabetes, lowering glucose mainly by reducing hepatic glucose production. Hold it for 48 hours before and after IV contrast because the combination raises the risk of lactic acidosis and acute kidney injury. Take it with meals to reduce GI upset; used alone it does not cause hypoglycemia.

Lisinopril is an ACE inhibitor that lowers blood pressure and reduces cardiac workload in hypertension and heart failure. Watch for a persistent dry cough, hyperkalemia, and the rare but emergent angioedema, and remember it is contraindicated in pregnancy. Monitor potassium and renal function, and teach the client to rise slowly to avoid orthostatic hypotension.

Metoprolol is a beta-blocker that slows heart rate and lowers blood pressure in hypertension, angina, and heart failure. Hold the dose and notify the provider if the pulse is below 60 or systolic BP is below 100, and never stop it abruptly because rebound tachycardia and hypertension can follow. Use it cautiously in asthma and watch for bradycardia and fatigue.

Albuterol is a short-acting beta-2 agonist that relaxes bronchial smooth muscle, making it the rescue inhaler for acute bronchospasm in asthma and COPD. Expect side effects of tachycardia, tremor, and jitteriness from beta stimulation. When both are ordered, use albuterol before an inhaled corticosteroid so the airways open first; rinsing the mouth is needed after the corticosteroid, not after albuterol.

Levothyroxine is synthetic thyroid hormone used to replace what the gland cannot make in hypothyroidism. Take it on an empty stomach in the morning, 30–60 minutes before food, for consistent absorption; signs of too much mimic hyperthyroidism (palpitations, weight loss, heat intolerance). It is lifelong therapy, and TSH is monitored every 6–12 weeks until the dose is stable.