Penicillins
The "-cillin" drugs. The #1 thing to assess is allergy.
Penicillins (amoxicillin, ampicillin, penicillin G, piperacillin) destroy the bacterial cell wall. They are widely used and generally safe, but allergy is the central nursing concern.
- Allergy is the priority: ask about prior reactions before giving. A true allergy can cause anaphylaxis — keep epinephrine and emergency equipment available, especially for the first dose.
- Common side effects: GI upset, diarrhea, rash.
- Amoxicillin can be taken with or without food; report rash, wheezing, or swelling immediately.
Before giving any "-cillin," ask the client about previous reactions and what happened. A rash is concerning; throat swelling, wheezing, or difficulty breathing signals anaphylaxis. Penicillin allergy is one of the most common and most tested drug allergies.
Every key point in this guide fits on one free printable page. Jump to the free cheatsheet PDF →
Cephalosporins
The "cef-/ceph-" drugs. Cross-allergy with penicillin and a reaction with alcohol.
Cephalosporins (cephalexin, cefazolin, ceftriaxone, cefepime) also work on the bacterial cell wall and are grouped into "generations" with broadening coverage.
- Cross-sensitivity with penicillin: structurally similar, so there's a small risk of allergy in penicillin-allergic clients — use caution and avoid in those with a history of anaphylaxis to penicillin.
- Alcohol: some cephalosporins cause a disulfiram-like reaction (flushing, nausea, vomiting, palpitations) with alcohol — teach clients to avoid alcohol during and shortly after therapy.
If the drug starts with cef- or ceph- (cefazolin, ceftriaxone, cephalexin), it's a cephalosporin. Ask about penicillin allergy, and teach clients to avoid alcohol.
Macrolides
The "-thromycin" drugs — a common alternative for penicillin-allergic clients.
Macrolides (azithromycin, erythromycin, clarithromycin) stop bacterial protein synthesis. They are often used for respiratory infections and in penicillin-allergic clients.
- Common side effects: GI upset (nausea, cramping, diarrhea) — erythromycin especially.
- QT prolongation and many drug interactions (they affect liver enzymes) — watch with other QT-prolonging drugs.
- Azithromycin ("Z-Pak") is a short course; take exactly as directed.
Azithromycin, erythromycin, clarithromycin — the "-thromycin" ending is a macrolide. Think GI upset and QT prolongation, and it's a go-to when the client is allergic to penicillin.
Tetracyclines
The "-cycline" drugs. Sun, dairy, and pregnancy are the test points.
Tetracyclines (doxycycline, tetracycline, minocycline) inhibit bacterial protein synthesis and treat acne, Lyme disease, Rocky Mountain spotted fever, and more.
- Photosensitivity: sunburn easily — use sunscreen and protective clothing.
- Chelation: avoid dairy, antacids, calcium, and iron, which bind the drug and block absorption.
- Contraindicated in pregnancy and children under 8 — they stain developing teeth and affect bone growth.
- Take with a full glass of water and stay upright to prevent esophageal irritation; don't take expired tetracycline (toxic).
Tetracyclines permanently stain developing teeth and can affect bone growth, so they're contraindicated in pregnancy, breastfeeding, and children under 8 years. Also separate them from dairy, antacids, and iron, which keep the drug from being absorbed.
Aminoglycosides & Vancomycin
Powerful IV antibiotics that are hard on the kidneys and ears — monitor levels.
These drugs treat serious infections but are nephrotoxic and ototoxic, so blood levels and organ function are monitored closely.
- Aminoglycosidesgentamicin, tobramycin, amikacin
- Nephrotoxic + ototoxic. Monitor BUN/creatinine, hearing/balance, and peak and trough levels. Ototoxicity worsens with loop diuretics.
- Vancomycin
- For MRSA and serious gram-positive infections. Monitor trough levels and kidney function. Infuse slowly (≥60 min) to prevent "red man syndrome."
If vancomycin is infused too fast, it causes red man syndrome: flushing and redness of the face, neck, and upper body (from histamine release). Infuse it over at least 60 minutes. Both vancomycin and aminoglycosides require monitoring of drug levels and kidney function for nephrotoxicity and ototoxicity.
For aminoglycosides, the trough is drawn just before the next dose (lowest level — checks for toxicity) and the peak shortly after the dose (highest level — checks effectiveness). Vancomycin is usually monitored by trough.
? What is the difference between why you draw a peak vs a trough level?
Fluoroquinolones
The "-floxacin" drugs — powerful, but watch the tendons.
Fluoroquinolones (ciprofloxacin, levofloxacin, moxifloxacin) treat UTIs, respiratory, and GI infections.
- Boxed warning: tendon rupture / tendinitis — highest risk in older adults, those on corticosteroids, and transplant clients. Report tendon pain or swelling and stop the drug.
- Photosensitivity and QT prolongation.
- Avoid dairy, antacids, and iron (reduce absorption); can cause CNS effects (dizziness, confusion).
Fluoroquinolones can cause tendinitis and tendon rupture (often the Achilles), especially in older adults and clients taking corticosteroids. Teach clients to report any new tendon or joint pain, swelling, or popping, to avoid strenuous exercise, and to stop the drug and call the provider if it occurs.
Sulfonamides
"Sulfa" drugs — allergy, fluids, and serious skin reactions.
Sulfonamides — most commonly trimethoprim-sulfamethoxazole (Bactrim, Septra) — treat UTIs and other infections.
- Sulfa allergy is common — assess before giving.
- Increase fluid intake to prevent crystalluria (crystals in the urine / kidney injury).
- Risk of Stevens-Johnson syndrome — report any rash, blistering, or peeling immediately.
- Photosensitivity; avoid in late pregnancy and newborns (risk of kernicterus).
Teach clients on sulfonamides to drink plenty of water (about 8 glasses/day) to keep urine flowing and prevent crystals from forming in the kidneys. And treat any new rash as a possible Stevens-Johnson warning — report it right away.
Antivirals, Antifungals & Key Teaching
Beyond antibiotics — plus the teaching that applies to every anti-infective.
Antivirals
- Acyclovir / valacyclovir: herpes and shingles. Start early; maintain hydration (IV acyclovir can be nephrotoxic). Not a cure — controls outbreaks.
- Oseltamivir (Tamiflu): influenza — most effective within 48 hours of symptom onset.
Antifungals
- Azoles (fluconazole, ketoconazole): hepatotoxic (monitor LFTs) with many drug interactions.
- Nystatin: oral thrush — "swish and swallow" to coat the mouth.
- Amphotericin B ("ampho-terrible"): serious systemic fungal infections — nephrotoxic with chills, fever, and shaking during infusion (pre-medicate and infuse slowly).
Teaching That Applies to All Anti-Infectives
- Finish the entire course, even after feeling better — prevents relapse and resistance.
- Obtain a culture before the first dose when ordered, but don't delay urgent antibiotics.
- Watch for superinfection — C. difficile diarrhea, oral or vaginal yeast — from disrupted normal flora.
- Take doses evenly spaced (around the clock) to keep steady blood levels; don't share or save antibiotics.
Amphotericin B is famous for its toxicity — nephrotoxicity and infusion reactions (fever, chills, rigors). Clients are pre-medicated (antipyretics, antihistamines) and it's infused slowly with close monitoring. The nickname helps you remember to watch the kidneys and the infusion.
? Why does nystatin need to stay in contact with the mouth after it's given?
Frequently Asked Questions
Common student questions on this topic.
Can a client allergic to penicillin take a cephalosporin?
Why is it important to finish the full course of antibiotics?
What teaching is important for tetracyclines like doxycycline?
What must be monitored with aminoglycosides and vancomycin?
What is the boxed warning for fluoroquinolones?
How is nystatin used for oral thrush?
Quick-Reference Cheatsheet
Every key point from this guide on a single printable page.
Anti-Infective Medications Cheatsheet
Free, printable PDF · no spam · returning visitors skip the email step.