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.
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
| Mechanism | Drug Classes | Key Point |
|---|---|---|
| Cell Wall Synthesis Inhibitors | Penicillins, Cephalosporins, Carbapenems, Vancomycin | Bactericidal |
| Protein Synthesis Inhibitors | Macrolides, Aminoglycosides, Tetracyclines | Some bacteriostatic |
| DNA/RNA Synthesis Inhibitors | Fluoroquinolones, Metronidazole, Rifampin | Bactericidal |
| Folate Synthesis Inhibitors | Sulfonamides, Trimethoprim | Often combined (Bactrim) |
Penicillins (Suffix: -cillin)
| Generic Name | Brand Name | Spectrum | Key Points |
|---|---|---|---|
| amoxicillin | Amoxil | Broad | Most common; available as suspension |
| amoxicillin/clavulanate | Augmentin | Broad (beta-lactamase resistant) | Keep suspension refrigerated |
| penicillin VK | Pen-VK | Narrow | Strep throat treatment |
| ampicillin | Various | Broad | Often IV; used for meningitis |
Allergy Alert: Penicillin allergies can be life-threatening. Cross-reactivity with cephalosporins is approximately 1-2%.
Cephalosporins
| Generation | Examples | Brand Names | Coverage |
|---|---|---|---|
| 1st | cephalexin, cefazolin | Keflex, Ancef | Gram-positive focus |
| 2nd | cefuroxime, cefaclor | Ceftin, Ceclor | Improved gram-negative |
| 3rd | ceftriaxone, cefdinir | Rocephin, Omnicef | Broad gram-negative |
| 4th | cefepime | Maxipime | Extended spectrum |
| 5th | ceftaroline | Teflaro | MRSA coverage |
Macrolides (Suffix: -thromycin)
| Generic Name | Brand Name | Key Points |
|---|---|---|
| azithromycin | Zithromax, Z-pack | QT prolongation risk; 5-day course |
| clarithromycin | Biaxin | Drug interactions (CYP3A4) |
| erythromycin | Various | GI side effects; many interactions |
Fluoroquinolones (Suffix: -floxacin)
| Generic Name | Brand Name | Key Points |
|---|---|---|
| ciprofloxacin | Cipro | Avoid with dairy/antacids; photosensitivity |
| levofloxacin | Levaquin | Once daily; respiratory infections |
| moxifloxacin | Avelox | No renal adjustment needed |
Black Box Warning: Tendon rupture, peripheral neuropathy, CNS effects
Tetracyclines
| Generic Name | Brand Name | Key Points |
|---|---|---|
| doxycycline | Vibramycin, Doryx | Take with full glass of water; photosensitivity |
| tetracycline | Sumycin | Avoid dairy; don't give to children <8 years |
| minocycline | Minocin | Vertigo/dizziness common |
Key Interactions: Dairy products, antacids, iron decrease absorption
Antiviral Medications
| Condition | Generic Name | Brand Name | Key Points |
|---|---|---|---|
| Herpes/Shingles | acyclovir | Zovirax | Maintain hydration |
| Herpes/Shingles | valacyclovir | Valtrex | Prodrug of acyclovir; better absorption |
| Influenza | oseltamivir | Tamiflu | Start within 48 hours of symptoms |
| HIV | Many combinations | Biktarvy, Descovy, Truvada | Strict adherence required |
| Hepatitis C | sofosbuvir/velpatasvir | Epclusa | Curative in most cases |
Antifungal Medications
| Generic Name | Brand Name | Use | Key Points |
|---|---|---|---|
| fluconazole | Diflucan | Yeast infections | Many drug interactions |
| itraconazole | Sporanox | Systemic fungal infections | Take with food |
| terbinafine | Lamisil | Nail fungus | Liver monitoring |
| nystatin | Mycostatin | Oral/topical candida | Swish and swallow |
| clotrimazole | Lotrimin | Topical fungal | OTC available |
Analgesic Medications
Opioid Analgesics (Schedule II unless noted)
| Generic Name | Brand Name | Relative Potency | Schedule |
|---|---|---|---|
| morphine | MS Contin, Roxanol | 1 (reference) | C-II |
| oxycodone | OxyContin, Percocet | 1.5x morphine | C-II |
| hydrocodone | Vicodin, Norco | Similar to morphine | C-II |
| hydromorphone | Dilaudid | 4-5x morphine | C-II |
| fentanyl | Duragesic (patch) | 80-100x morphine | C-II |
| codeine | Tylenol #3 | 0.1x morphine | C-II |
| tramadol | Ultram | Weak opioid + SNRI | C-IV |
Common Side Effects: Constipation, nausea, sedation, respiratory depression Antidote: Naloxone (Narcan)
Non-Opioid Analgesics
| Generic Name | Brand Name | Max Daily Dose | Key Points |
|---|---|---|---|
| acetaminophen | Tylenol | 3,000-4,000 mg | Hepatotoxicity risk; in many combinations |
| ibuprofen | Advil, Motrin | 3,200 mg (Rx); 1,200 mg (OTC) | GI bleeding risk; avoid in kidney disease |
| naproxen | Aleve, Naprosyn | 1,500 mg | Longer acting than ibuprofen |
| meloxicam | Mobic | 15 mg | Once daily NSAID |
| celecoxib | Celebrex | 400 mg | COX-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 Name | Brand Name | Key Points |
|---|---|---|
| fluoxetine | Prozac | Long half-life; many interactions |
| sertraline | Zoloft | Most commonly prescribed |
| paroxetine | Paxil | Withdrawal symptoms; weight gain |
| escitalopram | Lexapro | Well-tolerated; anxiety |
| citalopram | Celexa | QT prolongation at high doses |
Black Box Warning: Increased suicidality in young adults (under 25)
SNRIs (Serotonin-Norepinephrine Reuptake Inhibitors)
| Generic Name | Brand Name | Key Points |
|---|---|---|
| duloxetine | Cymbalta | Also for neuropathy, fibromyalgia |
| venlafaxine | Effexor XR | Blood pressure monitoring; taper slowly |
Other Antidepressants
| Generic Name | Brand Name | Class | Key Points |
|---|---|---|---|
| bupropion | Wellbutrin | NDRI | No sexual side effects; seizure risk |
| trazodone | Desyrel | SARI | Often used for sleep |
| mirtazapine | Remeron | Tetracyclic | Weight gain; sedation |
Anxiolytics (Anti-anxiety)
Benzodiazepines (Suffix: -azepam, -am - Schedule IV)
| Generic Name | Brand Name | Duration | Key Points |
|---|---|---|---|
| alprazolam | Xanax | Short | High abuse potential |
| lorazepam | Ativan | Short-intermediate | Available IV; no active metabolites |
| diazepam | Valium | Long | Muscle relaxant; multiple uses |
| clonazepam | Klonopin | Long | Also for seizures |
Side Effects: Sedation, dependence, respiratory depression Antidote: Flumazenil
Non-Benzodiazepine Anxiolytics
| Generic Name | Brand Name | Key Points |
|---|---|---|
| buspirone | BuSpar | Non-controlled; takes 2-4 weeks to work |
| hydroxyzine | Vistaril, Atarax | Antihistamine; also for itching |
Antiseizure/Anticonvulsant Medications
| Generic Name | Brand Name | Key Points |
|---|---|---|
| phenytoin | Dilantin | NTI drug; gingival hyperplasia |
| valproic acid | Depakote | Teratogenic; monitor liver/platelets |
| carbamazepine | Tegretol | NTI drug; many interactions |
| levetiracetam | Keppra | Few interactions; first-line |
| lamotrigine | Lamictal | Rash risk; titrate slowly |
| gabapentin | Neurontin | Also for neuropathy; not controlled |
| pregabalin | Lyrica | Schedule V; neuropathy |
| topiramate | Topamax | Weight 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.
| Class | Example | Key Counseling/Warning |
|---|---|---|
| Penicillins | amoxicillin | Cross-allergy with cephalosporins possible |
| Cephalosporins | cephalexin | Caution if severe penicillin allergy |
| Macrolides | azithromycin | Many drug interactions (CYP) |
| Fluoroquinolones | ciprofloxacin | Tendon rupture; avoid with antacids/dairy |
| Tetracyclines | doxycycline | Photosensitivity; avoid in pregnancy/children |
| Sulfonamides | sulfamethoxazole/trimethoprim | Sun 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.
| Drug | Schedule | Note |
|---|---|---|
| morphine | C-II | Reference opioid |
| oxycodone | C-II | Often combined with acetaminophen |
| hydrocodone/APAP | C-II | Watch acetaminophen ceiling (4 g/day) |
| codeine | C-II to C-V (combo) | Antitussive in low-dose combos |
| tramadol | C-IV | Lowers 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.
| Class | Example | Note |
|---|---|---|
| SSRI | sertraline, fluoxetine | First-line; 2-4 week onset |
| SNRI | venlafaxine, duloxetine | Also for neuropathic pain |
| TCA | amitriptyline | Anticholinergic; overdose risk |
| MAOI | phenelzine | Tyramine/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.
What is the antidote for an opioid overdose such as morphine or oxycodone?
Flumazenil
Naloxone (Narcan)
Vitamin K
Protamine sulfate
A patient is dispensed ciprofloxacin. An appropriate auxiliary counseling point is to:
Take with a calcium-rich antacid for best absorption
Separate from antacids, dairy, and iron by about 2 hours
Take only on an empty stomach with grapefruit juice
Double the dose if a dose is missed
A patient asks how long their new SSRI will take to relieve depression. The pharmacist will explain it typically takes:
A few hours
1 to 2 days
2 to 4 weeks
6 months
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