Pharmacology

Pharmacology for nursing practice is the applied study of drug action, drug safety, and the nursing responsibilities that surround every dose given. This article is the shared core content for both the NCLEX-RN and the NCLEX-PN tracks. Scope of practice differences are noted where they matter.

Core Concepts: Pharmacokinetics and Pharmacodynamics

Pharmacokinetics is what the body does to the drug. Four phases:

• Absorption: movement of drug from the site of administration into the bloodstream. Intravenous drugs bypass absorption entirely and are 100 percent bioavailable. Oral drugs are the slowest and most variable. Food, gastric pH, and gut motility all change absorption.
• Distribution: movement of drug from blood into tissues. Affected by blood flow, protein binding, and lipid solubility. Only the free (unbound) fraction is pharmacologically active. In low albumin states such as malnutrition, liver disease, or nephrotic syndrome, more free drug circulates and toxicity can occur at "normal" doses. Highly protein bound drugs such as warfarin and phenytoin compete for binding sites and can displace one another.
• Metabolism (biotransformation): primarily hepatic, largely by the cytochrome P450 enzyme system. Enzyme inducers (rifampin, phenytoin, carbamazepine, phenobarbital, St. John's wort) speed metabolism and lower serum levels of other drugs. Enzyme inhibitors (many azole antifungals, macrolides such as erythromycin and clarithromycin, grapefruit juice, some protease inhibitors) slow metabolism and raise levels, increasing toxicity risk.
• Excretion: primarily renal. Declining creatinine clearance means drug accumulation. Always check renal function before nephrotoxic or renally cleared drugs (aminoglycosides, vancomycin, digoxin, metformin, lithium, many direct oral anticoagulants).

First-pass effect: oral drugs absorbed from the gut travel through the portal vein to the liver and may be substantially metabolized before reaching systemic circulation. This is why sublingual, buccal, transdermal, rectal, and parenteral routes produce higher bioavailability and why the oral dose of a drug such as morphine is much larger than the intravenous dose.

Half-life is the time for serum concentration to fall by 50 percent. It takes roughly four to five half-lives to reach steady state on a fixed schedule, and roughly four to five half-lives to clear a drug after it is stopped. This explains why antidepressant effects take weeks and why a loading dose is used when a rapid therapeutic level is needed.

Pharmacodynamics is what the drug does to the body.

• Agonist: binds a receptor and produces the response (albuterol at beta-2 receptors).
• Antagonist: binds a receptor and blocks the response (naloxone at opioid receptors, metoprolol at beta-1 receptors).
• Partial agonist: produces a submaximal response (buprenorphine).
• Therapeutic index: the ratio of toxic dose to therapeutic dose. A narrow therapeutic index means small dosing changes cause toxicity, so serum levels are monitored. Classic examples: digoxin, lithium, phenytoin, theophylline, warfarin, vancomycin, aminoglycosides.
• Peak and trough: the peak is the highest serum concentration and reflects toxicity risk; the trough is drawn immediately before the next dose and reflects whether the level is staying therapeutic.

Drug Nomenclature and Classification

Every drug has a chemical name, a generic name (one per drug, used on the NCLEX), and one or more trade names. Learn generics. Recognizing stems is a high-yield shortcut:

• -pril = ACE inhibitor (lisinopril, enalapril)
• -sartan = angiotensin II receptor blocker (losartan, valsartan)
• -olol = beta blocker (metoprolol, atenolol)
• -dipine = dihydropyridine calcium channel blocker (amlodipine, nifedipine)
• -statin = HMG-CoA reductase inhibitor (atorvastatin, simvastatin)
• -prazole = proton pump inhibitor (omeprazole, pantoprazole)
• -tidine = histamine-2 receptor blocker (famotidine)
• -cillin = penicillin class antibiotic
• cef- or ceph- = cephalosporin
• -floxacin = fluoroquinolone
• -mycin or -micin = aminoglycoside or macrolide depending on the drug, check carefully
• -cycline = tetracycline
• -azole = antifungal (fluconazole) or antiprotozoal (metronidazole)
• -vir = antiviral
• -pam or -lam = benzodiazepine (lorazepam, alprazolam)
• -barbital = barbiturate
• -triptyline or -ipramine = tricyclic antidepressant
• -parin = low molecular weight heparin (enoxaparin, dalteparin)
• -ase = thrombolytic enzyme (alteplase)
• -mab = monoclonal antibody
• -ide in loop diuretics (furosemide, bumetanide)

The Nursing Process Applied to Medication Administration

Assessment. Before giving any drug, know the indication, the usual dose range, the route, and the expected action. Assess the parameters that the drug acts on and the parameters that make it unsafe: apical pulse before digoxin and beta blockers, blood pressure before antihypertensives and nitrates, respiratory rate and sedation level before opioids, blood glucose before insulin, potassium before digoxin or a potassium-sparing diuretic, and renal and hepatic function for drugs cleared by those organs. Obtain a complete allergy history including the nature of the reaction, and a full medication reconciliation that includes over-the-counter drugs, herbals, and supplements.

Analysis and planning. Identify the therapeutic goal and the measurable outcome. "Pain rated 3 or less within 60 minutes" is a usable outcome; "patient comfortable" is not.

Implementation. Verify the order, perform the safety checks below, use two patient identifiers, and never administer a medication another nurse prepared or one you did not personally verify.

Evaluation. Reassess for both therapeutic effect and adverse effect within the drug's expected time to onset. Document the effect, not just the administration. Pain reassessment is generally within 15 to 30 minutes for intravenous analgesia and within 45 to 60 minutes for oral analgesia.

Scope note. In most jurisdictions the practical or vocational nurse may administer oral, topical, subcutaneous, intramuscular, and other basic route medications, monitors for effects, reinforces teaching that the registered nurse initiated, and reports findings. The practical nurse generally does not perform initial patient assessment, does not push intravenous medications, does not titrate vasoactive or other continuous infusions, does not administer blood products, and does not initiate patient teaching plans. The registered nurse retains responsibility for assessment, clinical judgment, titration, and evaluation. Always verify the specific state nurse practice act and facility policy.

The Rights of Medication Administration

The traditional five rights, expanded in current practice:

1. Right patient: two identifiers, never the room number. Compare the identifiers to the medication administration record and the patient's identification band.
2. Right drug: check the label against the order. Beware look-alike and sound-alike pairs such as hydralazine and hydroxyzine, metoprolol tartrate and metoprolol succinate, insulin glargine and insulin lispro, celecoxib and citalopram.
3. Right dose: recalculate independently. Question any dose requiring more than two tablets or an unusually large volume.
4. Right route: never assume. Some drugs are fatal by the wrong route, for example vincristine given intrathecally, or concentrated potassium chloride given as an intravenous push.
5. Right time: most facilities allow a window of 30 minutes before or after the scheduled time for routine drugs. Time-critical drugs such as insulin, antibiotics, anticoagulants, and antiparkinson agents have tighter windows.
6. Right documentation: chart immediately after administration, never before.
7. Right reason or indication: the drug should match the diagnosis.
8. Right response or evaluation: did it work.
9. Right to refuse: a competent patient may refuse. Educate, document, and notify the prescriber.
10. Right education: the patient should know what the drug is for and what to report.

Perform three checks of the label: when removing the drug from storage, when preparing it, and at the bedside before administering.

Independent double check. Two qualified clinicians independently verify, without prompting each other, the drug, concentration, dose, pump settings, and patient identity. Required by most policies for insulin, heparin and other anticoagulants, chemotherapy, patient-controlled analgesia, epidural infusions, and all high-alert pediatric and neonatal drugs.

Routes and Administration Techniques

• Oral: give with a full glass of water unless fluid restricted. Do not crush enteric-coated or extended-release forms (labels such as EC, SR, XL, XR, CR, LA); crushing can deliver a fatal bolus. Sublingual tablets dissolve under the tongue and are not swallowed.
• Enteral tube: use liquid formulations when available, flush before and after, and give drugs separately. Hold tube feeding around phenytoin and levothyroxine because feedings markedly reduce absorption.
• Subcutaneous: 45 to 90 degree angle, small volume (generally 1 mL or less). Rotate sites. For enoxaparin, use the "love handle" area of the abdomen at least 2 inches from the umbilicus, do not expel the air bubble in the prefilled syringe, do not aspirate, and do not massage the site.
• Intramuscular: ventrogluteal is the preferred site in adults because it is away from major nerves and vessels; vastus lateralis is preferred in infants. Typical adult volume limit is 3 mL in a large muscle. Use the Z-track technique for irritating drugs such as iron dextran and haloperidol decanoate.
• Intradermal: 5 to 15 degree angle, bevel up, forming a wheal. Used for tuberculin skin testing and allergy testing.
• Intravenous: fastest onset and least forgiving. Verify compatibility, dilution, and maximum push rate before administering. Assess site patency before and after.
• Transdermal: remove the old patch before applying a new one and document removal. Rotate sites, wear gloves for nitroglycerin and hormone patches, and never cut a reservoir patch.
• Ophthalmic: instill in the lower conjunctival sac, apply punctal pressure for 30 to 60 seconds to limit systemic absorption, and wait 5 minutes between different eye drops. Give drops before ointment.
• Inhaled: with multiple inhalers, give the bronchodilator first, then the corticosteroid, and have the patient rinse the mouth after inhaled corticosteroids to prevent oral candidiasis. Use a spacer when available.

Dosage Calculation

Basic formula: Desired divided by Have, multiplied by Quantity.

Intravenous flow rate in mL per hour equals total volume in mL divided by time in hours. Drip rate in drops per minute equals volume in mL, multiplied by the drop factor in drops per mL, divided by time in minutes.

Weight-based infusions such as mcg/kg/min require converting units carefully. Always convert pounds to kilograms by dividing by 2.2. For pediatric patients, calculate the safe dose range from the reference (for example mg/kg/day divided by the number of doses) and compare it to the ordered dose; if the ordered dose falls outside the safe range, hold and clarify with the prescriber.

Major Drug Classes by Body System

Cardiovascular

• ACE inhibitors (lisinopril): lower blood pressure and reduce cardiac remodeling. Adverse effects: persistent dry cough, hyperkalemia, first-dose hypotension, acute kidney injury, and rarely angioedema, which is an emergency. Contraindicated in pregnancy. If cough is intolerable, an angiotensin receptor blocker is the usual substitute.
• ARBs (losartan): similar profile without the cough. Still cause hyperkalemia and are contraindicated in pregnancy.
• Beta blockers (metoprolol, atenolol, carvedilol): decrease heart rate, contractility, and blood pressure. Hold and notify for apical pulse under 60 or systolic blood pressure under 90 unless otherwise ordered. Never stop abruptly because rebound tachycardia, hypertension, and angina can occur. Use caution in asthma with nonselective agents. Beta blockers mask the tachycardia and tremor of hypoglycemia, which is a key teaching point in diabetes.
• Calcium channel blockers: dihydropyridines (amlodipine, nifedipine) act mainly on vessels and cause peripheral edema, flushing, and headache. Nondihydropyridines (verapamil, diltiazem) also slow the heart rate and are used for rate control. Verapamil commonly causes constipation. Grapefruit juice raises levels.
• Diuretics: loop diuretics (furosemide, bumetanide) are potent and cause hypokalemia, hyponatremia, hypomagnesemia, hypocalcemia, dehydration, and ototoxicity when pushed rapidly. Give intravenous furosemide slowly. Thiazides (hydrochlorothiazide) cause hypokalemia, hyperglycemia, hyperuricemia, and hypercalcemia. Potassium-sparing agents (spironolactone, triamterene) cause hyperkalemia; spironolactone also causes gynecomastia. Teach patients to take diuretics in the morning to avoid nocturia and to weigh daily, reporting a gain of 2 to 3 pounds in a day or about 5 pounds in a week.
• Digoxin: positive inotrope, negative chronotrope. Therapeutic serum range is roughly 0.5 to 2.0 ng/mL, with 0.5 to 0.9 ng/mL targeted in heart failure. Take the apical pulse for a full minute and hold for a rate under 60 in an adult. Early toxicity presents as anorexia, nausea, vomiting, fatigue, visual disturbance including yellow-green halos, and dysrhythmias. Hypokalemia potentiates digoxin toxicity, so watch potassium closely in patients also taking loop diuretics. The antidote is digoxin immune Fab.
• Nitrates (nitroglycerin): venodilation reduces preload and relieves angina. Sublingual dosing for an outpatient is one tablet, repeated every 5 minutes up to three doses, with emergency services called per current guidance if pain is unrelieved. Expect headache. Absolutely contraindicated with phosphodiesterase-5 inhibitors such as sildenafil or tadalafil because of profound hypotension. Hold for systolic blood pressure under 90. Transdermal nitrates require a nitrate-free interval, typically 10 to 12 hours, to prevent tolerance.
• Statins: lower low-density lipoprotein. Monitor for myalgia and, rarely, rhabdomyolysis; teach patients to report unexplained muscle pain, tenderness, weakness, or dark urine. Monitor liver enzymes at baseline. Avoid grapefruit juice with simvastatin, lovastatin, and atorvastatin. Contraindicated in pregnancy.
• Antidysrhythmics: amiodarone is broadly effective but causes pulmonary toxicity, thyroid dysfunction (both hypo and hyper), hepatotoxicity, corneal microdeposits, blue-gray skin discoloration, and QT prolongation. Adenosine is given as a rapid intravenous push followed immediately by a saline flush and produces a brief period of asystole.
• Vasoactive infusions (registered nurse scope): norepinephrine, dopamine, epinephrine, phenylephrine, vasopressin, nitroglycerin drip, nitroprusside, and dobutamine are titrated to a hemodynamic target. Give through a central line when possible because extravasation of a vasoconstrictor causes tissue necrosis; the antidote for that extravasation is phentolamine infiltrated locally. Nitroprusside carries a risk of cyanide and thiocyanate toxicity with prolonged or high-dose use and must be protected from light.

Anticoagulants, Antiplatelets, and Thrombolytics

• Heparin (unfractionated): monitored by aPTT, with a therapeutic target commonly 1.5 to 2.5 times the control value, or by anti-Xa level per facility protocol. Antidote is protamine sulfate. Watch for heparin-induced thrombocytopenia, an immune reaction in which the platelet count falls, typically 5 to 10 days after exposure, and the patient paradoxically clots. If suspected, stop all heparin including flushes and notify the provider.
• Enoxaparin: low molecular weight heparin, more predictable, usually no routine monitoring, dose-reduced in renal impairment. Same subcutaneous technique points listed above.
• Warfarin: vitamin K antagonist. Monitored by prothrombin time and INR, with a usual therapeutic INR of 2.0 to 3.0 for atrial fibrillation and venous thromboembolism, and 2.5 to 3.5 for a mechanical mitral valve. Onset takes several days, so heparin bridging is common. Antidote is vitamin K (phytonadione); fresh frozen plasma or prothrombin complex concentrate is used for urgent reversal. Teach consistent, not zero, intake of vitamin K rich foods such as spinach, kale, broccoli, and Brussels sprouts. Contraindicated in pregnancy. Many interactions, including antibiotics, amiodarone, and NSAIDs.
• Direct oral anticoagulants: apixaban and rivaroxaban (factor Xa inhibitors, reversal agent andexanet alfa) and dabigatran (direct thrombin inhibitor, reversal agent idarucizumab). No routine INR monitoring.
• Antiplatelets: aspirin, clopidogrel, ticagrelor. Bleeding and bruising are the main risks. Clopidogrel effect is reduced by strong CYP2C19 inhibitors such as omeprazole.
• Thrombolytics (alteplase): dissolve existing clot in acute ischemic stroke, ST elevation myocardial infarction, and massive pulmonary embolism. Absolute exclusions include active internal bleeding, recent intracranial hemorrhage, and recent intracranial or intraspinal surgery. During and after infusion, minimize venipunctures and injections and monitor neurologic status closely.

Universal anticoagulant teaching: use a soft toothbrush and an electric razor, avoid contact sports, report black tarry stools, pink or brown urine, bleeding gums, nosebleeds that will not stop, unusual bruising, or a fall with head strike, and wear medical identification.

Endocrine

• Insulin: the only insulin given intravenously is regular insulin. Approximate profiles: rapid acting (lispro, aspart, glulisine) onset about 15 minutes, peak about 1 hour, give with the meal in front of the patient; short acting regular onset about 30 to 60 minutes, peak about 2 to 4 hours; intermediate NPH onset about 1 to 2 hours, peak about 4 to 12 hours (the only cloudy insulin, and the only one routinely mixed); long acting glargine and detemir with no pronounced peak and no mixing with other insulins. When mixing, draw clear before cloudy (regular before NPH) after injecting air into both vials. Hypoglycemia signs: shakiness, diaphoresis, tachycardia, hunger, confusion, irritability. Treat a conscious patient with 15 grams of fast-acting carbohydrate, recheck in 15 minutes, and repeat as needed; treat an unconscious patient with intravenous dextrose or glucagon.
• Oral antidiabetics: metformin does not cause hypoglycemia alone and carries a risk of lactic acidosis; hold it before and after iodinated contrast studies per protocol and check renal function. Sulfonylureas (glipizide, glyburide) do cause hypoglycemia. SGLT2 inhibitors (-flozin) cause genital mycotic and urinary infections and euglycemic ketoacidosis. GLP-1 agonists (-tide) cause nausea and delay gastric emptying.
• Levothyroxine: take in the morning on an empty stomach with water, at least 30 to 60 minutes before food, and separate from calcium, iron, and antacids by about 4 hours. Signs of excess dose mimic hyperthyroidism: tachycardia, palpitations, weight loss, heat intolerance, insomnia. Lifelong therapy.
• Corticosteroids (prednisone, methylprednisolone): expect hyperglycemia, immunosuppression and masked infection, fluid retention, hypokalemia, mood changes, osteoporosis and cushingoid features with long-term use, and delayed wound healing. Take with food. Never stop abruptly after prolonged therapy because adrenal insufficiency can result; taper.

Neurologic and Psychiatric

• Opioids (morphine, hydromorphone, fentanyl, oxycodone): the most dangerous adverse effect is respiratory depression, and sedation precedes it, so monitor the level of arousal. Constipation is the effect that does not develop tolerance, so start a bowel regimen. Antidote is naloxone, which has a shorter duration than most opioids, so continued monitoring and repeat dosing may be needed. Hydromorphone is substantially more potent than morphine milligram for milligram, a frequent source of serious errors.
• Non-opioid analgesics: acetaminophen has a maximum of 4 grams per day for most healthy adults, with lower limits in liver disease, chronic alcohol use, and older adults; the antidote for overdose is acetylcysteine. NSAIDs cause gastrointestinal bleeding, kidney injury, and fluid retention, and should be taken with food and avoided with anticoagulants.
• Benzodiazepines (lorazepam, diazepam, midazolam): sedation, respiratory depression especially when combined with opioids, and dependence. Antidote is flumazenil, used cautiously because it can precipitate seizures in chronic users.
• Antiepileptics: phenytoin has a narrow therapeutic range of roughly 10 to 20 mcg/mL and causes gingival hyperplasia (teach meticulous oral care), nystagmus and ataxia with toxicity, and severe skin reactions. Intravenous phenytoin is compatible with normal saline only, not dextrose, and must be given slowly. Valproate and carbamazepine require monitoring of liver function and blood counts; carbamazepine is a strong enzyme inducer. Levetiracetam is associated with behavioral changes.
• Antidepressants: SSRIs take 2 to 4 weeks for mood response, and energy may improve before mood, transiently increasing suicide risk in young patients. Watch for serotonin syndrome: agitation, hyperthermia, hyperreflexia, clonus, diaphoresis, and tremor, especially when an SSRI is combined with another serotonergic drug such as tramadol, triptans, linezolid, or St. John's wort. Tricyclics cause anticholinergic effects, orthostatic hypotension, and cardiac conduction problems, and are dangerous in overdose. MAO inhibitors require a tyramine-restricted diet (avoid aged cheese, cured and smoked meats, fermented soy, tap beer, and overripe or fermented foods) to prevent hypertensive crisis, and require a washout period of about 2 weeks when switching to or from an SSRI.
• Lithium: therapeutic serum range about 0.6 to 1.2 mEq/L; levels above 1.5 mEq/L are toxic. Early toxicity presents as nausea, vomiting, diarrhea, fine tremor, and thirst; advancing toxicity brings coarse tremor, confusion, ataxia, and seizures. Teach adequate and consistent sodium and fluid intake, since dehydration, sodium loss, thiazide diuretics, NSAIDs, and ACE inhibitors all raise lithium levels. Monitor thyroid and renal function.
• Antipsychotics: first generation agents (haloperidol, fluphenazine) most often cause extrapyramidal symptoms including acute dystonia, akathisia, pseudoparkinsonism, and tardive dyskinesia, which may be irreversible. Second generation agents (risperidone, olanzapine, quetiapine, aripiprazole) carry a greater metabolic burden with weight gain, hyperglycemia, and dyslipidemia. Neuroleptic malignant syndrome is a medical emergency: high fever, lead-pipe rigidity, altered mental status, autonomic instability, and elevated creatine kinase. Clozapine requires ongoing absolute neutrophil count monitoring because of agranulocytosis risk.

Respiratory

• Short-acting beta-2 agonists (albuterol): rescue therapy; expect tachycardia and tremor. Increasing rescue inhaler use signals worsening control.
• Inhaled corticosteroids (fluticasone, budesonide): controller therapy, not rescue. Rinse the mouth after use.
• Anticholinergics (ipratropium, tiotropium): dry mouth; caution in narrow-angle glaucoma and urinary retention.
• Leukotriene modifiers (montelukast): controller therapy with a warning for neuropsychiatric effects.
• Theophylline: narrow therapeutic range of roughly 10 to 20 mcg/mL, with toxicity presenting as tachycardia, nausea, restlessness, and seizures. Caffeine adds to the effect.

Gastrointestinal

• Proton pump inhibitors: take before the first meal of the day. Long-term risks include Clostridioides difficile infection, fracture, hypomagnesemia, and vitamin B12 deficiency.
• Histamine-2 blockers and antacids: antacids interfere with the absorption of many drugs, so separate doses by 1 to 2 hours. Aluminum-containing antacids cause constipation, magnesium-containing antacids cause diarrhea.
• Antiemetics: ondansetron prolongs the QT interval. Promethazine is a vesicant, causing severe tissue injury with extravasation, and is preferably given by a route other than peripheral intravenous push. Metoclopramide can cause extrapyramidal symptoms and tardive dyskinesia.

Anti-infectives

• Obtain cultures before the first antibiotic dose whenever feasible, and teach patients to complete the full course.
• Penicillins and cephalosporins: monitor for allergy and anaphylaxis; cross-sensitivity with cephalosporins exists but is lower than historically taught.
• Vancomycin: monitor trough levels and renal function. Infuse over at least 60 minutes; rapid infusion causes an infusion reaction with flushing of the face, neck, and upper torso. Ototoxicity and nephrotoxicity are the main toxicities.
• Aminoglycosides (gentamicin, tobramycin): nephrotoxic and ototoxic. Monitor peaks, troughs, creatinine, and hearing, and report tinnitus or new hearing loss.
• Fluoroquinolones: tendinitis and tendon rupture, QT prolongation, photosensitivity, and central nervous system effects. Separate from antacids, calcium, iron, and zinc by at least 2 hours.
• Tetracyclines and doxycycline: avoid in pregnancy and in young children because of tooth discoloration; chelated by dairy, antacids, and iron; photosensitivity.
• Macrolides: gastrointestinal upset, QT prolongation, and significant CYP interactions with erythromycin and clarithromycin.
• Sulfonamides (trimethoprim-sulfamethoxazole): encourage fluids, watch for rash including Stevens-Johnson syndrome, hyperkalemia, and interaction with warfarin.
• Metronidazole: avoid alcohol during therapy and for at least 3 days after because of a disulfiram-like reaction; may cause a metallic taste and dark urine.
• Antitubercular therapy: isoniazid causes peripheral neuropathy, prevented with pyridoxine (vitamin B6), and hepatotoxicity. Rifampin turns urine, sweat, and tears orange, permanently stains soft contact lenses, and reduces the effectiveness of oral contraceptives. Ethambutol causes optic neuritis with changes in visual acuity and red-green color discrimination.

Oncology and Immune

Cytotoxic chemotherapy causes bone marrow suppression with a nadir typically 7 to 14 days after administration, mucositis, alopecia, nausea, and infertility. Teach infection precautions and report a temperature of 38 degrees Celsius or 100.4 degrees Fahrenheit or higher as a potential neutropenic emergency. Many agents are vesicants requiring immediate action for extravasation. Doxorubicin is cardiotoxic with a lifetime cumulative dose limit, cisplatin is nephrotoxic and ototoxic, vincristine causes peripheral neuropathy and is fatal if given intrathecally, and methotrexate is rescued with leucovorin. Preparation and administration of chemotherapy require specialized certification.

High-Alert Medications

High-alert medications carry a heightened risk of significant harm when used in error. Commonly designated classes include:

• Insulins, especially concentrated formulations
• Anticoagulants including heparin, warfarin, and direct oral agents
• Opioids and other sedating agents including patient-controlled and epidural analgesia
• Concentrated electrolytes, especially potassium chloride, hypertonic sodium chloride, and magnesium sulfate
• Chemotherapeutic and other cytotoxic agents
• Neuromuscular blocking agents such as succinylcholine, rocuronium, and vecuronium, which cause paralysis without sedation or analgesia and must never be given to a patient who is not intubated and ventilated
• Vasoactive and inotropic infusions
• Moderate sedation agents

Safety controls for these drugs include independent double checks, standardized concentrations, smart pump dose-error reduction software, removal of concentrated electrolytes from floor stock, and tall man lettering for look-alike names.

Potassium chloride is never given by intravenous push. It must be diluted, given by infusion pump, and typically infused no faster than 10 mEq per hour through a peripheral line, with faster rates only in a monitored setting with central access per policy. Assess urine output before administering potassium.

Therapeutic Drug Monitoring and Key Reference Values

Drug	Usual therapeutic range	Key toxicity signs
Digoxin	0.5 to 2.0 ng/mL (0.5 to 0.9 in heart failure)	Anorexia, nausea, visual halos, bradycardia, dysrhythmia
Lithium	0.6 to 1.2 mEq/L	Tremor, vomiting, diarrhea, ataxia, confusion, seizure
Phenytoin	10 to 20 mcg/mL	Nystagmus, ataxia, slurred speech, confusion
Theophylline	10 to 20 mcg/mL	Tachycardia, restlessness, nausea, seizure
Warfarin	INR 2.0 to 3.0 (2.5 to 3.5 mechanical mitral valve)	Bleeding
Heparin	aPTT 1.5 to 2.5 times control	Bleeding, thrombocytopenia

Antidotes and Reversal Agents

• Opioid: naloxone
• Benzodiazepine: flumazenil
• Acetaminophen: acetylcysteine
• Warfarin: vitamin K (phytonadione)
• Heparin: protamine sulfate
• Digoxin: digoxin immune Fab
• Magnesium sulfate: calcium gluconate
• Iron: deferoxamine
• Ethylene glycol or methanol: fomepizole
• Organophosphate: atropine and pralidoxime
• Methotrexate: leucovorin
• Dabigatran: idarucizumab
• Apixaban or rivaroxaban: andexanet alfa
• Anticholinergic toxicity: physostigmine
• Extravasation of a vasoconstrictor: phentolamine

Special Populations

Older adults. Reduced renal clearance, reduced hepatic metabolism, lower lean body mass, and lower albumin all increase drug effect. Polypharmacy compounds risk. Beers Criteria drugs to use with caution include benzodiazepines, first-generation antihistamines such as diphenhydramine, strong anticholinergics, and certain sedative hypnotics because of falls, delirium, and urinary retention. Start low and go slow.

Pediatrics. Dosing is weight based or body-surface-area based. Always verify the safe dose range. Avoid aspirin in children and adolescents with viral illness because of Reye syndrome.

Pregnancy and lactation. The former lettered categories were replaced by the Pregnancy and Lactation Labeling Rule, which uses narrative risk summaries. Known teratogens or drugs contraindicated in pregnancy include warfarin, ACE inhibitors and ARBs, isotretinoin, methotrexate, statins, tetracyclines, and valproate.

Renal and hepatic impairment. Adjust or avoid renally cleared and hepatically metabolized drugs, and monitor levels when available.

Medication Errors and Safety Culture

If an error occurs: assess the patient first, provide any needed intervention, notify the provider, document the facts in the medical record objectively, and complete the incident or occurrence report. The occurrence report is a quality improvement document and is not filed in the patient chart, nor is its existence charted.

Preventive practices include avoiding error-prone abbreviations (write "unit" not "U", "daily" not "QD", "every other day" not "QOD", avoid "MS" for morphine sulfate or magnesium sulfate), always using a leading zero before a decimal (0.5 mg) and never a trailing zero (5 mg, not 5.0 mg), reading back verbal and telephone orders, limiting verbal orders to emergencies, and using barcode-assisted medication administration.

Nurses have the professional duty to question and clarify an order that appears unsafe, incomplete, or inappropriate. Administering a knowingly unsafe order does not shift liability away from the nurse.

Patient Education Principles

• Teach the drug name, purpose, dose, timing, route, and what to do about a missed dose.
• Teach the most likely adverse effects and the specific findings that require a call to the provider.
• Assess health literacy, language, vision, dexterity, and cost barriers before assuming nonadherence is a choice.
• Use plain language, teach one concept at a time, and confirm understanding with the teach-back method, which is asking the patient to explain the instruction in their own words.
• Reinforce not stopping a drug because the patient feels better, which is critical for antibiotics, antihypertensives, antiepileptics, and antituberculars.
• Address over-the-counter and herbal products explicitly. Examples of clinically important herbals: St. John's wort induces enzymes and reduces the effect of many drugs while increasing serotonin syndrome risk; ginkgo, ginger, garlic, and ginseng increase bleeding risk.
• Provide written material at an accessible reading level and include the caregiver when appropriate.

Study Strategy for the Licensure Exam

Learn drugs by class, then learn the exceptions. For any class, be able to state the prototype, the mechanism in one sentence, the two or three assessment findings you check before giving it, the two or three adverse effects you monitor for, the antidote if there is one, and the single most important teaching point. On the exam, when a question asks what the nurse does first, apply airway, breathing, and circulation, then safety, then the least invasive appropriate action. When a question asks which patient or finding to report, look for the one that is unexpected, life-threatening, or a known sentinel toxicity of the drug named in the stem.

This page is independent study material for nursing licensure exam preparation. NCLEX-RN® and NCLEX-PN® are registered trademarks of the National Council of State Boards of Nursing (NCSBN). This content is not produced, reviewed, or endorsed by NCSBN. Always verify clinical information against current facility policy, drug references, and your nursing program's curriculum before applying it in practice.