Antiparasitics, Antifungals & Antivirals – Comprehensive Study Notes

Course Logistics & Administrative Reminders

• Antiviral & Antifungal “Classification Form” (NOT antacids worksheet) is due tonight at 11:59 PM; deadline was extended.

• ALL unfinished ATI modules or other assignments must be completed by Friday to satisfy course requirements (late = zero points but still mandatory).

• Short lecture today; detailed medication review during the afternoon study-hall/“study call.”

• Instructor will upload study-hall materials/Kahoot on Blackboard for students who must miss the live session (e.g., skills checkoffs).

“Pet Poops” Ice-Breaker

• Lighthearted activity shown prior to lecture.

Therapy for Bacterial Infection – Part 2 (Today’s Focus)

• Covers Antiparasitics, Antifungals, Antivirals.

• Quick clarification on bactericidal vs. bacteriostatic from prior content: “-cidal” = kills bacteria directly or indirectly; preventing infection may still involve killing.

Antiparasitics

Key Biology Concepts

• Parasites live inside host blood cells, organs, or structures (esp. intestines, vagina).

• Examples

  • Malaria → enters bloodstream, migrates to liver.

  • Helminths → intestinal worms.

  • Trichomoniasis ("trich") → STI in reproductive tract of all genders.

Drug #1 – Metronidazole (Flagyl)

• Classification: Anti-infective / Antiprotozoal.

• Expected Action: Damages DNA of anaerobic organisms → inhibits replication.

• Therapeutic Uses: Trichomoniasis, Giardiasis, intestinal & systemic amoebiasis; also common for bacterial vaginosis (“BV”).

• Routes/Administration

  • PO: tabs, caps, SR caps; crush regular tabs if needed.

  • Give PO 1 h before or 2 h after meals for best absorption.

  • IV: reconstitute, dilute, infuse slowly.

  • Topical cream & vaginal gel also available.

• Precautions: Use cautiously in HF, hepatic/renal impairment, seizure d/o, blood dyscrasias.

• Contra-indications: Active CNS disease; pregnancy risk – teratogenic (birth defects).

• Major Interactions

  • Alcohol → disulfiram-like reaction: facial flushing, N/V, hypotension, sweating, SOB, dizziness, anxiety.

  • Celexa (citalopram), IV nitroglycerin, sulfamethoxazole, phenobarbital, lithium.

• Adverse Reactions

  • GI (N/V, cramps), metallic taste, anorexia, dry mouth, dark urine.

  • CNS: headache, vertigo, ataxia → severe: seizures, peripheral neuropathy.

• Nursing Interventions

  • Monitor GI & CNS status; d/c if seizures/neuropathy.

  • Teach expected benign effects (metallic taste, dark urine) vs. reportable effects.

  • Alcohol abstinence is critical.

Drug #2 – Chloroquine

• Classification: Antimalarial / Antiprotozoal.

• MOA: Unknown; drug of choice for prophylaxis & treatment of malaria.

• Dosing for travelers: 500\,\text{mg} once weekly

  • Start 1–2 weeks before travel, continue during stay, and 4 weeks after leaving endemic area.

• Weight-based dosing for children.

• Routes: PO (preferred) or IM.

• Precautions: Optic neuritis, psoriasis, liver disease, pregnancy/breast-feeding.

• Contra-indications: Hypersensitivity, prior retinopathy from similar drugs.

• Interactions: Minimal/none documented.

• Adverse Reactions (usually only at high doses): Visual changes, N/D.

• Nursing/Teaching

  • Report vision changes; sunglasses help photophobia.

  • Take with or just after food if GI upset.

Antifungals

Fungal Biology Snapshot

• Fungi are plant-like, thrive in dark, warm, moist areas; eat dead tissue.

• Common infections

  • Tinea pedis (athlete’s foot), tinea corporis (ringworm), tinea cruris (jock itch).

  • Vaginal candidiasis very common due to female anatomy.

Drug Group – Polyene Antibiotics

Prototype: Amphotericin B

• Expected Action: Disrupts fungal cell-wall integrity.

• Therapeutic Uses: Severe systemic fungal infections, disseminated candida.

• Routes: IV (main), PO suspension (swish & swallow e.g., nystatin), topical.

• IV Specifics

  • Daily dosing; dilute correctly; infuse slowly.

  • Weight-based; used only when infection could be fatal.

• Precautions: Bone-marrow suppression, anemia, renal insufficiency.

• Contra-indications: Hypersensitivity, breastfeeding.

• Key Drug Interactions: Corticosteroids, digoxin, aminoglycosides, cyclosporine, furosemide (↑nephrotoxicity), vancomycin.

• Major Adverse Effects

  • Infusion reaction (1–2 h after start): chills, fever, N/V, tachycardia, hypotension, headache (resolves ~4 h).

  • Nephrotoxicity, hypokalemia & hypomagnesemia.

  • Anemia (RBC suppression).

  • Thrombophlebitis at IV site.

• Nursing Interventions

  • Pre-medicate with diphenhydramine + acetaminophen.

  • Monitor VS throughout infusion; stop if severe reaction.

  • Check labs: BUN, creatinine, K^{+}, Mg^{2+}, CBC.

  • Track I&O and daily weights.

  • Use large vein, observe for phlebitis; discontinue for respiratory distress.

• Client Education

  • Explain infusion-reaction symptoms & importance of reporting.

  • Report fatigue (possible anemia).

  • Keep all lab appointments.

Drug Group – Azoles

Prototype: Ketoconazole

• Expected Action: Blocks fungal cell-wall synthesis.

• Uses: Yeast & tinea infections; sometimes systemic mycoses.

• Formulations: PO tablet, topical cream, medicated shampoo.

• Interesting Clinical Pearl: Dermatologists often prescribe shampoo for scalp mycoses leading to hair loss.

• Precautions: Pregnancy/lactation; oddly, caution in onychomycosis (nail fungus).

• Interactions

  • Antacids → raise gastric pH, impair absorption (needs acidic environment).

  • Warfarin → ↑bleeding risk.

• Adverse Reactions

  • Topical: burning, itching, erythema, localized hypersensitivity.

  • Systemic: Hepatotoxicity, GI upset, drowsiness, dizziness.

• Nursing/Teaching

  • Monitor LFTs; teach signs of liver injury: abdominal pain, jaundice, fatigue, anorexia.

  • Take with acidic beverage (water, soda, coffee, juice) & food to minimize GI upset.

  • Avoid antacids; separate by >2 h if absolutely needed.

  • Caution with driving until CNS effects known.

Antivirals

Virology Basics

• Viruses become intracellular parasites; hide within host cells, making treatment hard.

• Antibiotics are ineffective against viral illnesses (e.g., common cold).

• Illustrative viruses in lecture: HSV-1 (cold sores), HSV-2 (genital), VZV (chickenpox & shingles), HHV-4 (Epstein–Barr → mono), Influenza, HIV.

Drug – Acyclovir (Zovirax)

• Classification: Antiviral.

• Expected Action: Inhibits viral DNA replication.

• Therapeutic Uses: HSV-1, HSV-2, VZV (shingles/chickenpox); severe infections in immunocompromised patients.

• Routes/Forms

  • IV for severe/immunocompromised.

  • PO caps, tabs, oral suspension for routine therapy.

  • Topical cream/ointment for cold sores, genital lesions, mild skin involvement.

• Administration Pearls

  • Wear gloves when applying topical to prevent self-inoculation.

  • For IV: Infuse slowly; encourage ↑oral fluids for >2 h after infusion.

• Precautions: Renal insufficiency, neurological disorders, dehydration (adds renal risk).

• Interactions: Probenecid & other nephrotoxic drugs ↑ risk of renal & CNS toxicity.

• Adverse Reactions

  • Topical: transient burning/itching.

  • PO: GI upset, headache, vertigo.

  • IV: Nephrotoxicity, rare CNS effects (restlessness, tremors, seizures, psychosis), thrombophlebitis.

• Nursing Interventions

  • Monitor skin & GI symptoms; bun/creatinine pre- & intra-therapy.

  • Hydrate patient; ensure adequate urine output.

  • Inspect IV site; stop infusion if phlebitis or CNS S/S emerge.

• Client Teaching

  • Don’t scratch lesions; avoid eye contact with cream.

  • Take PO with food if needed; increase fluid intake.

  • Report IV site pain, persistent rash, or neuro symptoms immediately.

  • Use condoms/abstain during active HSV outbreaks; acyclovir reduces but does not eliminate transmission.

Study & Exam Guidance From Instructor

• Focus on unique adverse reactions, lab monitoring, patient-teaching points for each drug.

• Know which lab you would order (e.g., BUN/Cr for kidneys, LFT for liver, CBC for anemia) – not numeric values.

• No dosage calculations on upcoming exam.

• Blueprint & Kahoot posted; attend 1 PM study hall if possible (or review recording/materials on Blackboard).

Ethical/Practical Notes

• Counseling on alcohol abstinence with metronidazole is ethical duty (prevent harm).

• Emphasize glove use for topical antivirals to protect both patient & clinician.

• Travel prophylaxis (chloroquine) prevents disease importation, public-health importance.

Course Logistics & Administrative Reminders

• Antiviral & Antifungal “Classification Form” (NOT antacids worksheet) is due tonight at 11:59 PM; the deadline was extended to accommodate unforeseen circumstances and ensure all students have ample time to submit this critical assignment for foundational understanding.

• ALL unfinished ATI modules or other assignments must be completed by Friday to satisfy course requirements. While late submissions will receive zero points, their completion is still mandatory for course progression and to meet clinical hour equivalents.

• Short lecture today, focusing on new therapy classes; a more detailed and interactive medication review with practical application will occur during the afternoon study-hall/“study call.”

• Instructor will upload comprehensive study-hall materials and the Kahoot game on Blackboard for students who must miss the live session (e.g., due to scheduled skills checkoffs or other clinical duties).

“Pet Poops” Ice-Breaker

• Lighthearted activity shown briefly prior to the lecture to foster engagement and create a relaxed learning environment.

Therapy for Bacterial Infection – Part 2 (Today’s Focus)

• This session covers treatments for Antiparasitics, Antifungals, and Antivirals, moving beyond purely bacterial infections to address a broader spectrum of microbial pathogens.

• Quick clarification revisited from prior content: “-cidal” agents kill bacteria directly (e.g., by destroying cell walls), whereas “-static” agents inhibit bacterial growth (e.g., by interfering with protein synthesis), allowing the host immune system to eliminate the infection. Preventing infection, in a broader sense, may still involve bacterial eradication.

Antiparasitics

Key Biology Concepts

• Parasites are organisms that live on or in a host and obtain their nourishment from the host; they often reside inside host blood cells, organ tissues, or specific structures (especially intestines and vaginal tracts), adapting to their host's environment.

• Examples:

  • Malaria → Caused by Plasmodium parasites, transmitted by mosquitoes. Once in the human body, they enter the bloodstream, migrate to the liver for an initial growth phase, and then re-enter the bloodstream to infect red blood cells, leading to cyclical fever.

  • Helminths → Broad category for parasitic worms (e.g., roundworms, tapeworms, flukes) that often infest the gastrointestinal tract, causing various digestive and systemic symptoms.

  • Trichomoniasis ("trich") → A sexually transmitted infection (STI) caused by Trichomonas vaginalis, a flagellated protozoan. It primarily infects the reproductive tract and urethra in all genders, leading to inflammation and discomfort.

Drug #1 – Metronidazole (Flagyl)

• Classification: Anti-infective / Antiprotozoal; specifically effective against anaerobic bacteria and certain protozoa.

• Expected Action: Metronidazole acts as a prodrug that is non-enzymatically reduced by anaerobic organisms. The activated form then damages the DNA structure of these anaerobic organisms, leading to DNA strand breakage and loss of helical structure, which in turn inhibits nucleic acid synthesis and replication, effectively killing the pathogen.

• Therapeutic Uses: Widely used for Trichomoniasis, Giardiasis (an intestinal protozoal infection), intestinal & systemic amoebiasis (caused by Entamoeba histolytica), and is also very common for treating bacterial vaginosis (“BV”) due to its efficacy against anaerobic bacteria responsible for the condition.

• Routes/Administration:

  • PO: Available as tablets, capsules, and sustained-release (SR) capsules. Regular tablets can be crushed if needed for patients with difficulty swallowing.

  • For optimal absorption and efficacy, administer PO doses 1 hour before or 2 hours after meals.

  • IV: Requires reconstitution and dilution according to pharmacy guidelines and must be infused slowly to minimize adverse reactions like thrombophlebitis.

  • Topical cream & vaginal gel formulations are also available for localized infections like rosacea or bacterial vaginosis.

• Precautions: Exercise caution in patients with a history of heart failure (HF), significant hepatic (liver) or renal (kidney) impairment (as it is metabolized in the liver and excreted by the kidneys), seizure disorders (due to potential CNS effects), and blood dyscrasias (e.g., neutropenia, agranulocytosis) as it can exacerbate these conditions.

• Contra-indications: Absolutely contraindicated in patients with active central nervous system (CNS) disease due to the risk of severe neurological adverse effects. Also, a significant pregnancy risk – it is teratogenic (known to cause birth defects) in the first trimester, thus generally avoided during early pregnancy unless absolutely necessary.

• Major Interactions:

  • Alcohol → disulfiram-like reaction: Concurrent ingestion of alcohol (including alcohol-containing medications or products) can lead to a severe and uncomfortable reaction characterized by facial flushing, intense nausea and vomiting, significant hypotension, profuse sweating, shortness of breath, dizziness, and anxiety. This reaction is due to the inhibition of aldehyde dehydrogenase by metronidazole, leading to acetaldehyde accumulation.

  • Other interactions include Celexa (citalopram), IV nitroglycerin, sulfamethoxazole, phenobarbital, and lithium, which can alter metronidazole metabolism or enhance its effects/toxicity.

• Adverse Reactions:

  • GI: Common effects include nausea, vomiting, abdominal cramps, a persistent and unpleasant metallic taste in the mouth, anorexia, and dry mouth. These are usually mild to moderate.

  • Other benign effects: Urine may appear reddish-brown or dark due to a metabolite.

  • CNS: Headache, vertigo (dizziness), and ataxia (impaired coordination) are common. Severe reactions, though rare, can include seizures and peripheral neuropathy (tingling, numbness, weakness), which necessitate immediate discontinuation.

• Nursing Interventions:

  • Continuously monitor the patient's GI status (e.g., severity of nausea, incidence of vomiting) and CNS status (e.g., changes in mental status, signs of gait instability, seizures). Discontinue the drug immediately if seizures or signs of peripheral neuropathy emerge.

  • Educate the client about expected benign effects such as the metallic taste and dark urine, reassuring them that these are typically harmless, and distinguish these from reportable adverse effects.

  • Absolute alcohol abstinence is critical during treatment and for at least 72 hours after the last dose to prevent the severe disulfiram-like reaction.

Drug #2 – Chloroquine

• Classification: Antimalarial / Antiprotozoal. It is a 4-aminoquinoline derivative.

• MOA: While the exact molecular mechanism remains unknown, it is thought to concentrate in the parasite's food vacuole and interfere with the detoxification of heme, which is a byproduct of hemoglobin digestion by the parasite. Chloroquine is considered the drug of choice for prophylaxis and treatment of uncomplicated malaria caused by susceptible Plasmodium species (excluding some resistant strains).

• Dosing for travelers: For malaria prophylaxis, the typical adult dose is 500 \text{ mg} (chloroquine phosphate) once weekly.

  • Administration: Must be started 1–2 weeks before entering an endemic area, continued throughout the stay, and for a full 4 weeks after leaving the endemic area to cover the lifecycle of the parasite.

• Weight-based dosing is crucial for children to ensure efficacy and minimize toxicity.

• Routes: Primarily PO (preferred due to convenience and safety profile) or IM (used in severe cases or when oral intake is not possible).

• Precautions: Requires careful use in patients with a history of optic neuritis, psoriasis (can exacerbate skin condition), liver disease (due to hepatic metabolism), and during pregnancy/breast-feeding due to potential risks to the fetus/infant.

• Contra-indications: Hypersensitivity to chloroquine or related compounds, and a history of prior retinopathy (retinal damage) from chloroquine or other 4-aminoquinoline drugs due to irreversible visual impairment risk.

• Interactions: Generally minimal to none documented, which simplifies its co-administration with other medications.

• Adverse Reactions (usually only at high doses or with prolonged use): Visual changes (e.g., blurred vision, difficulty focusing), and gastrointestinal upset (nausea/diarrhea).

• Nursing/Teaching:

  • Instruct patients to immediately report any vision changes, difficulties with reading, or blurred vision. Regular ophthalmic exams are recommended for long-term use.

  • Advise wearing sunglasses to help manage photophobia (light sensitivity) if it occurs.

  • To minimize GI upset, instruct patients to take the medication with or just after food.

Antifungals

Fungal Biology Snapshot

• Fungi are eukaryotic organisms, distinct from bacteria and viruses, characterized by their plant-like structures and cell walls containing chitin. They thrive in dark, warm, moist environments, making skin folds, between toes, and mucous membranes common sites of infection. Fungi are heterotrophic, meaning they derive nutrition by breaking down and eating dead tissue or keratin.

• Common infections:

  • Tinea pedis (athlete’s foot), tinea corporis (ringworm), tinea cruris (jock itch): These are dermatophyte infections affecting the skin, hair, and nails, characterized by itching, redness, and characteristic ring-like lesions.

  • Vaginal candidiasis (yeast infection) is very common in females due to the anatomy and warm, moist environment of the vagina, often exacerbated by antibiotic use or hormonal changes.

Drug Group – Polyene Antibiotics

Prototype: Amphotericin B

• Expected Action: Amphotericin B is a broad-spectrum fungicidal agent. Its mechanism involves binding irreversibly to ergosterol (a vital component of the fungal cell membrane, analogous to cholesterol in mammalian cells). This binding creates pores and channels in the fungal cell membrane, leading to increased permeability, leakage of intracellular ions (K^{+}, Mg^{2+}) and molecules, and ultimately disrupts fungal cell-wall integrity, causing cell lysis and death. This