3.3 Anti-infective, Analgesic, and CNS Medications

Key Takeaways

  • Antibiotics are classified by mechanism: cell wall synthesis inhibitors (penicillins, cephalosporins), protein synthesis inhibitors (macrolides, tetracyclines), DNA/RNA inhibitors (fluoroquinolones).
  • Penicillin allergy may cross-react with cephalosporins; always check allergy status before dispensing.
  • Opioid analgesics (morphine, oxycodone, hydrocodone) are Schedule II controlled substances with addiction potential.
  • NSAIDs (ibuprofen, naproxen) can cause GI bleeding and should be used cautiously with anticoagulants.
  • Benzodiazepines (-azepam) are Schedule IV controlled substances used for anxiety and seizures; can cause dependence.
Last updated: June 2026

Quick Answer: This section covers three major drug categories: anti-infectives (antibiotics, antivirals, antifungals), analgesics (opioids, NSAIDs, acetaminophen), and CNS medications (antidepressants, anxiolytics, antiseizure drugs). Understanding mechanisms, common drugs, and key safety issues is essential.

Anti-infective Medications

Antibiotic Classes by Mechanism

MechanismDrug ClassesKey Point
Cell Wall Synthesis InhibitorsPenicillins, Cephalosporins, Carbapenems, VancomycinBactericidal
Protein Synthesis InhibitorsMacrolides, Aminoglycosides, TetracyclinesSome bacteriostatic
DNA/RNA Synthesis InhibitorsFluoroquinolones, Metronidazole, RifampinBactericidal
Folate Synthesis InhibitorsSulfonamides, TrimethoprimOften combined (Bactrim)

Penicillins (Suffix: -cillin)

Generic NameBrand NameSpectrumKey Points
amoxicillinAmoxilBroadMost common; available as suspension
amoxicillin/clavulanateAugmentinBroad (beta-lactamase resistant)Keep suspension refrigerated
penicillin VKPen-VKNarrowStrep throat treatment
ampicillinVariousBroadOften IV; used for meningitis

Allergy Alert: Penicillin allergies can be life-threatening. Cross-reactivity with cephalosporins is approximately 1-2%.

Cephalosporins

GenerationExamplesBrand NamesCoverage
1stcephalexin, cefazolinKeflex, AncefGram-positive focus
2ndcefuroxime, cefaclorCeftin, CeclorImproved gram-negative
3rdceftriaxone, cefdinirRocephin, OmnicefBroad gram-negative
4thcefepimeMaxipimeExtended spectrum
5thceftarolineTeflaroMRSA coverage

Macrolides (Suffix: -thromycin)

Generic NameBrand NameKey Points
azithromycinZithromax, Z-packQT prolongation risk; 5-day course
clarithromycinBiaxinDrug interactions (CYP3A4)
erythromycinVariousGI side effects; many interactions

Fluoroquinolones (Suffix: -floxacin)

Generic NameBrand NameKey Points
ciprofloxacinCiproAvoid with dairy/antacids; photosensitivity
levofloxacinLevaquinOnce daily; respiratory infections
moxifloxacinAveloxNo renal adjustment needed

Black Box Warning: Tendon rupture, peripheral neuropathy, CNS effects

Tetracyclines

Generic NameBrand NameKey Points
doxycyclineVibramycin, DoryxTake with full glass of water; photosensitivity
tetracyclineSumycinAvoid dairy; don't give to children <8 years
minocyclineMinocinVertigo/dizziness common

Key Interactions: Dairy products, antacids, iron decrease absorption

Antiviral Medications

ConditionGeneric NameBrand NameKey Points
Herpes/ShinglesacyclovirZoviraxMaintain hydration
Herpes/ShinglesvalacyclovirValtrexProdrug of acyclovir; better absorption
InfluenzaoseltamivirTamifluStart within 48 hours of symptoms
HIVMany combinationsBiktarvy, Descovy, TruvadaStrict adherence required
Hepatitis Csofosbuvir/velpatasvirEpclusaCurative in most cases

Antifungal Medications

Generic NameBrand NameUseKey Points
fluconazoleDiflucanYeast infectionsMany drug interactions
itraconazoleSporanoxSystemic fungal infectionsTake with food
terbinafineLamisilNail fungusLiver monitoring
nystatinMycostatinOral/topical candidaSwish and swallow
clotrimazoleLotriminTopical fungalOTC available

Analgesic Medications

Opioid Analgesics (Schedule II unless noted)

Generic NameBrand NameRelative PotencySchedule
morphineMS Contin, Roxanol1 (reference)C-II
oxycodoneOxyContin, Percocet1.5x morphineC-II
hydrocodoneVicodin, NorcoSimilar to morphineC-II
hydromorphoneDilaudid4-5x morphineC-II
fentanylDuragesic (patch)80-100x morphineC-II
codeineTylenol #30.1x morphineC-II
tramadolUltramWeak opioid + SNRIC-IV

Common Side Effects: Constipation, nausea, sedation, respiratory depression Antidote: Naloxone (Narcan)

Non-Opioid Analgesics

Generic NameBrand NameMax Daily DoseKey Points
acetaminophenTylenol3,000-4,000 mgHepatotoxicity risk; in many combinations
ibuprofenAdvil, Motrin3,200 mg (Rx); 1,200 mg (OTC)GI bleeding risk; avoid in kidney disease
naproxenAleve, Naprosyn1,500 mgLonger acting than ibuprofen
meloxicamMobic15 mgOnce daily NSAID
celecoxibCelebrex400 mgCOX-2 selective; less GI bleeding

NSAID Warnings: GI bleeding, cardiovascular risk (except aspirin), renal impairment

Central Nervous System (CNS) Medications

Antidepressants

SSRIs (Selective Serotonin Reuptake Inhibitors - Suffix: -oxetine, -pram)

Generic NameBrand NameKey Points
fluoxetineProzacLong half-life; many interactions
sertralineZoloftMost commonly prescribed
paroxetinePaxilWithdrawal symptoms; weight gain
escitalopramLexaproWell-tolerated; anxiety
citalopramCelexaQT prolongation at high doses

Black Box Warning: Increased suicidality in young adults (under 25)

SNRIs (Serotonin-Norepinephrine Reuptake Inhibitors)

Generic NameBrand NameKey Points
duloxetineCymbaltaAlso for neuropathy, fibromyalgia
venlafaxineEffexor XRBlood pressure monitoring; taper slowly

Other Antidepressants

Generic NameBrand NameClassKey Points
bupropionWellbutrinNDRINo sexual side effects; seizure risk
trazodoneDesyrelSARIOften used for sleep
mirtazapineRemeronTetracyclicWeight gain; sedation

Anxiolytics (Anti-anxiety)

Benzodiazepines (Suffix: -azepam, -am - Schedule IV)

Generic NameBrand NameDurationKey Points
alprazolamXanaxShortHigh abuse potential
lorazepamAtivanShort-intermediateAvailable IV; no active metabolites
diazepamValiumLongMuscle relaxant; multiple uses
clonazepamKlonopinLongAlso for seizures

Side Effects: Sedation, dependence, respiratory depression Antidote: Flumazenil

Non-Benzodiazepine Anxiolytics

Generic NameBrand NameKey Points
buspironeBuSparNon-controlled; takes 2-4 weeks to work
hydroxyzineVistaril, AtaraxAntihistamine; also for itching

Antiseizure/Anticonvulsant Medications

Generic NameBrand NameKey Points
phenytoinDilantinNTI drug; gingival hyperplasia
valproic acidDepakoteTeratogenic; monitor liver/platelets
carbamazepineTegretolNTI drug; many interactions
levetiracetamKeppraFew interactions; first-line
lamotrigineLamictalRash risk; titrate slowly
gabapentinNeurontinAlso for neuropathy; not controlled
pregabalinLyricaSchedule V; neuropathy
topiramateTopamaxWeight loss; kidney stones

Exam Tip: Know opioid schedules, antibiotic classes with their suffixes, and which drugs require monitoring (NTI drugs, warfarin, digoxin).


Antibiotic Classes and Auxiliary Counseling Points

Anti-infectives are heavily tested. Match the class to its stem and its key warning.

ClassExampleKey Counseling/Warning
PenicillinsamoxicillinCross-allergy with cephalosporins possible
CephalosporinscephalexinCaution if severe penicillin allergy
MacrolidesazithromycinMany drug interactions (CYP)
FluoroquinolonesciprofloxacinTendon rupture; avoid with antacids/dairy
TetracyclinesdoxycyclinePhotosensitivity; avoid in pregnancy/children
Sulfonamidessulfamethoxazole/trimethoprimSun sensitivity; sulfa allergy

Exam Trap: Fluoroquinolones and tetracyclines chelate with calcium, magnesium, iron, and antacids, reducing absorption. Separate dosing by 2 hours. Expect an auxiliary-label question on this.


Opioid Analgesics and the Naloxone Antidote

Opioids treat moderate-to-severe pain and are high-alert, controlled substances. Respiratory depression is the lethal risk.

DrugScheduleNote
morphineC-IIReference opioid
oxycodoneC-IIOften combined with acetaminophen
hydrocodone/APAPC-IIWatch acetaminophen ceiling (4 g/day)
codeineC-II to C-V (combo)Antitussive in low-dose combos
tramadolC-IVLowers seizure threshold

Exam Tip: The opioid reversal agent is naloxone (Narcan). Acetaminophen combination products carry a 4 g/day maximum to prevent liver toxicity, a frequent counseling and safety item.


Antidepressant Onset and Interactions

SSRIs and SNRIs take 2 to 4 weeks for full effect, a common counseling point. Combining serotonergic drugs risks serotonin syndrome.

ClassExampleNote
SSRIsertraline, fluoxetineFirst-line; 2-4 week onset
SNRIvenlafaxine, duloxetineAlso for neuropathic pain
TCAamitriptylineAnticholinergic; overdose risk
MAOIphenelzineTyramine/food and drug interactions

Worked Example: A patient on sertraline (SSRI) is prescribed tramadol; both raise serotonin, so the technician flags the combination for the pharmacist to assess serotonin-syndrome risk.

Test Your Knowledge

What is the antidote for an opioid overdose such as morphine or oxycodone?

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Test Your Knowledge

A patient is dispensed ciprofloxacin. An appropriate auxiliary counseling point is to:

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D
Test Your Knowledge

A patient asks how long their new SSRI will take to relieve depression. The pharmacist will explain it typically takes:

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D