Antivirals Antiprotozoals

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Information about Antivirals Antiprotozoals

Published on November 15, 2007

Author: girlie

Source: slideshare.net

Antivirals & Antiprotozoals

Virus Types DNA viruses Herpes viruses – chicken pox, shingles, herpes Adenoviruses – conjunctivitis, pharyngitis Hepadnaviruses – hepatitis B Papillomaviruses – warts RNA viruses Rubella – German measles Rhabdoviruses - rabies Picornaviruses – poliomyelitis, meningitis, colds Arboviruses – yellow fever Orthomyxoviruses – influenza Paramyxoviruses – measles & mumps Retroviruses - HIV

DNA viruses

Herpes viruses – chicken pox, shingles, herpes

Adenoviruses – conjunctivitis, pharyngitis

Hepadnaviruses – hepatitis B

Papillomaviruses – warts

RNA viruses

Rubella – German measles

Rhabdoviruses - rabies

Picornaviruses – poliomyelitis, meningitis, colds

Arboviruses – yellow fever

Orthomyxoviruses – influenza

Paramyxoviruses – measles & mumps

Retroviruses - HIV

Parasites Small, unicellular organisms Include: Protozoa Helminths Arthropods Broken into categories based on locomotion Examples of protozoal infections Amebiasis – Entamoeba histolytica Giardiasis – Giardia Lamblia Trichomoniasis – Trichomonas vaginalis Malaria – Plasmodium falciparum, p. vivax, P. malariae, P. ovale

Small, unicellular organisms

Include:

Protozoa

Helminths

Arthropods

Broken into categories based on locomotion

Examples of protozoal infections

Amebiasis – Entamoeba histolytica

Giardiasis – Giardia Lamblia

Trichomoniasis – Trichomonas vaginalis

Malaria – Plasmodium falciparum, p. vivax, P. malariae, P. ovale

Other Antivirals/Antiinfectives Antiinfluenza Antiherpes Flagyl Plaquenil Metronidazole Chloroquine Other Symmetrel Flumadine Relenza Tamiflu Amantadine Rimantadine Zanamivir Oseltamivir Zovirax Famvir Valtrex Denavir Acyclovir Famciclovir Valacyclovir Penciclovir Antivirals TRADE GENERIC CLASS

Antivirals: Indications Acyclovir, famciclovir, valacyclovir, penciclovir (only used topically)  inhibit viral DNA synthesis – highly selective for infected cells (all have similar chemical structure) HSV 1 & 2: acute infection & chronic suppression VZV: chicken pox & shingles EBV: mononucleosis Amantadine (also used in Parkinsons), rimantadine, zanamivir, oseltamivir – structurally similar to tricyclic amines  inhibit an early step in viral replication, also affect viral assembly Influenza A: amantadine & rimantadine Influenza A & B: zanamivir & oseltamivir Metronidazole Many protozoa, also used in many bacterial and amebic infections Chloroquine Malaria

Acyclovir, famciclovir, valacyclovir, penciclovir (only used topically)  inhibit viral DNA synthesis – highly selective for infected cells (all have similar chemical structure)

HSV 1 & 2: acute infection & chronic suppression

VZV: chicken pox & shingles

EBV: mononucleosis

Amantadine (also used in Parkinsons), rimantadine, zanamivir, oseltamivir – structurally similar to tricyclic amines  inhibit an early step in viral replication, also affect viral assembly

Influenza A: amantadine & rimantadine

Influenza A & B: zanamivir & oseltamivir

Metronidazole

Many protozoa, also used in many bacterial and amebic infections

Chloroquine

Malaria

Important Principles Peak viral activity occurs prior to Sx’s  effectiveness of drug depends on early initiation of Tx Viral agents work by inhibiting reproduction BUT do not eradicate latent viruses  elimination of virus is NOT complete BUT can assist in reducing & suppressing Sx’s Tx can reduce transmission rates in pregnancy & decreases morbidity/mortality associate with HSV infection

Peak viral activity occurs prior to Sx’s  effectiveness of drug depends on early initiation of Tx

Viral agents work by inhibiting reproduction BUT do not eradicate latent viruses  elimination of virus is NOT complete BUT can assist in reducing & suppressing Sx’s

Tx can reduce transmission rates in pregnancy & decreases morbidity/mortality associate with HSV infection

Antivirals: Patient Variables Geriatrics Generally effective & well tolerated Pediatrics Famciclovir & Valacyclovir: S&E in children < 18 yrs NOT established Acyclovir: S&E in children < 2 yr NOT established Amantadine & Rimantadine: S&E in children < 1 yr NOT established Pregnancy Famciclovir & Valacyclovir: Category B Acyclovir, Amantadine & Rimantadine: Category C Lactation Acyclovir, Amantadine & Rimantadine: in breast milk Famciclovir & Valacyclovir: Unknown

Geriatrics

Generally effective & well tolerated

Pediatrics

Famciclovir & Valacyclovir: S&E in children < 18 yrs NOT established

Acyclovir: S&E in children < 2 yr NOT established

Amantadine & Rimantadine: S&E in children < 1 yr NOT established

Pregnancy

Famciclovir & Valacyclovir: Category B

Acyclovir, Amantadine & Rimantadine: Category C

Lactation

Acyclovir, Amantadine & Rimantadine: in breast milk

Famciclovir & Valacyclovir: Unknown

Patient Ed: Genital Herpes Avoid sexual contact when visible lesions are present Does not cure viral infection, but can decrease severity & duration of outbreak Women may be at higher risk of cervical cancer  annual PAP

Avoid sexual contact when visible lesions are present

Does not cure viral infection, but can decrease severity & duration of outbreak

Women may be at higher risk of cervical cancer  annual PAP

Acyclovir (Zovirax) Pharmacokinetics Absorption 15-30% from GI; not affected by food; bioavailability decreases with increasing doses Can achieve therapeutic serum levels Distribution WIDE including: brain, kidney, lung, liver, muscles, spleen, uterus, vaginal mucosa, CSF (50% plasma), herpetic vesicular fluid Peak 1.5-2 hr; ½ life 3 hrs Protein-binding 9-33% Metabolism Liver Excretion - dependent on renal function Kidneys (parenteral 62-91% unchanged)

Pharmacokinetics

Absorption

15-30% from GI; not affected by food; bioavailability decreases with increasing doses

Can achieve therapeutic serum levels

Distribution

WIDE including: brain, kidney, lung, liver, muscles, spleen, uterus, vaginal mucosa, CSF (50% plasma), herpetic vesicular fluid

Peak 1.5-2 hr; ½ life 3 hrs

Protein-binding 9-33%

Metabolism

Liver

Excretion - dependent on renal function

Kidneys (parenteral 62-91% unchanged)

Acyclovir (Zovirax) Contraindications Hypersensitivity or intolerance Warnings / Precautions Extreme caution in decreased renal function Caution in poor hydration or w/nephrotoxic drugs  can precipitate ARF Consider obtaining viral culture 1% neurologic reaction – lethargy, obtundation, tremors, confusion, hallucinations, agitation, seizures, coma Testicular atrophy in rats Emergence of resistant viruses

Contraindications

Hypersensitivity or intolerance

Warnings / Precautions

Extreme caution in decreased renal function

Caution in poor hydration or w/nephrotoxic drugs  can precipitate ARF

Consider obtaining viral culture

1% neurologic reaction – lethargy, obtundation, tremors, confusion, hallucinations, agitation, seizures, coma

Testicular atrophy in rats

Emergence of resistant viruses

Acyclovir (Zovirax) Adverse effects COMMON: PO  GI: nausea, vomiting, diarrhea IV  inflammation or phlebitis Increased SE’s w/longer term use Drug interactions Probenecid  increases bioavailability & ½ life; may also decrease renal clearance & excretion AZT + Zovirax  may cause severe lethargy

Adverse effects

COMMON: PO  GI: nausea, vomiting, diarrhea

IV  inflammation or phlebitis

Increased SE’s w/longer term use

Drug interactions

Probenecid  increases bioavailability & ½ life; may also decrease renal clearance & excretion

AZT + Zovirax  may cause severe lethargy

Famciclovir (Famvir) Structurally similar to acyclovir – used as an alternative Decreased duration but not incidence of post-herpetic neuralgia age>50 Effective in treating first episodes & recurrences of HSV; also for chronic suppression of HSV as well as HBV Cross resistance observed Drug interactions Cimetidine, probenecid, theophylline increase levels; drug increases digoxin levels COMMON SE’s: headache, nausea, diarrhea

Structurally similar to acyclovir – used as an alternative

Decreased duration but not incidence of post-herpetic neuralgia age>50

Effective in treating first episodes & recurrences of HSV; also for chronic suppression of HSV as well as HBV

Cross resistance observed

Drug interactions

Cimetidine, probenecid, theophylline increase levels; drug increases digoxin levels

COMMON SE’s: headache, nausea, diarrhea

Valacyclovir (Valtrex) Warnings Thrombotic thrombocytopenic purpura / hemolytic uremic syndrome in HIV Caution in renal impairment Drug interactions Cimetidine & probenecid reduce rate but not extent of conversion of drug

Warnings

Thrombotic thrombocytopenic purpura / hemolytic uremic syndrome in HIV

Caution in renal impairment

Drug interactions

Cimetidine & probenecid reduce rate but not extent of conversion of drug

Amantadine (Symmetrel) Warnings / Precautions Observe closely if seizure Hx Caution in liver disease, psychosis or psychoneurosis, cardiac Hx (CHF), renal impairment CNS effects: blurred vision Development of resistant strains Do NOT D/C abruptly in Parkinsons Adverse effects Nausea, dizziness, lightheadedness, insomnia

Warnings / Precautions

Observe closely if seizure Hx

Caution in liver disease, psychosis or psychoneurosis, cardiac Hx (CHF), renal impairment

CNS effects: blurred vision

Development of resistant strains

Do NOT D/C abruptly in Parkinsons

Adverse effects

Nausea, dizziness, lightheadedness, insomnia

Amantadine (Symmetrel) Drug interactions Anticholinergic – may need to reduce dose if atropine-like effect occurs HCTZ – decreases urinary excretion  increases plasma concentration Overdosage Nausea, vomiting, anorexia, CNS effects Can cause death Notify HCP if Mood or mental changes, swelling of extremities, difficulty urinating, SOB

Drug interactions

Anticholinergic – may need to reduce dose if atropine-like effect occurs

HCTZ – decreases urinary excretion  increases plasma concentration

Overdosage

Nausea, vomiting, anorexia, CNS effects

Can cause death

Notify HCP if

Mood or mental changes, swelling of extremities, difficulty urinating, SOB

Rimantadine (Flumadine) Adverse effects MOST COMMON: GI & CNS Drug interactions Acetaminophen & ASA decrease peak concentration Cimetidine increases serum concentration

Adverse effects

MOST COMMON: GI & CNS

Drug interactions

Acetaminophen & ASA decrease peak concentration

Cimetidine increases serum concentration

Vancomycin (Vancocin) Mechanism of action Rarely used in primary care Prevents synthesis of bacterial cell wall by block peptidoglycan strand formation Indications IV for serious life-threatening staph or strept infections Drug of choice for severe cases of C. difficile Primary care use: Tx of pseudomembranous colitis caused by C. difficile & given PO if metronidazole contraindicated or ineffective

Mechanism of action

Rarely used in primary care

Prevents synthesis of bacterial cell wall by block peptidoglycan strand formation

Indications

IV for serious life-threatening staph or strept infections

Drug of choice for severe cases of C. difficile

Primary care use: Tx of pseudomembranous colitis caused by C. difficile & given PO if metronidazole contraindicated or ineffective

Clindamycin (Cleocin) Indications Reserved for serious infections where less toxic drugs are inappropriate Used for serious infections caused by strepto-, pneumo-, and staphylococci In primary care used in combination with tretinoin gel for Tx of acne vulgaris Can cause severe & possibly fatal colitis PCPs should work closely w/specialist in Tx of patients with this drug

Indications

Reserved for serious infections where less toxic drugs are inappropriate

Used for serious infections caused by strepto-, pneumo-, and staphylococci

In primary care used in combination with tretinoin gel for Tx of acne vulgaris

Can cause severe & possibly fatal colitis

PCPs should work closely w/specialist in Tx of patients with this drug

Nitrofurantoin (Macrobid et al) Indications UTI caused by: E. coli , enterococci, S. aureus , Kleibsiella and Enterobacter species Contraindications Not for use in impaired renal function or pregnancy Warnings/Precautions Acute pulmonary reactions: dyspnea, chest pain, cough, fever, chills Chronic pulmonary reactions seen in prolonged therapy Hemolytic anemia Hepatic reactions: hepatitis, cholestatic jaundice (rare fatalities)

Indications

UTI caused by: E. coli , enterococci, S. aureus , Kleibsiella and Enterobacter species

Contraindications

Not for use in impaired renal function or pregnancy

Warnings/Precautions

Acute pulmonary reactions: dyspnea, chest pain, cough, fever, chills

Chronic pulmonary reactions seen in prolonged therapy

Hemolytic anemia

Hepatic reactions: hepatitis, cholestatic jaundice (rare fatalities)

Nitrofurantoin (Macrobid et al) Patient variables Pediatric: contraindicated in age <1 mo Pregnancy: Category B Lactation: excreted in milk Adverse effects Peripheral neuropathy: may be severe or irreversible Superinfection MOST COMMON: anorexia, nausea, emesis Overdosage Vomiting

Patient variables

Pediatric: contraindicated in age <1 mo

Pregnancy: Category B

Lactation: excreted in milk

Adverse effects

Peripheral neuropathy: may be severe or irreversible

Superinfection

MOST COMMON: anorexia, nausea, emesis

Overdosage

Vomiting

Nitrofurantoin (Macrobid et al) Drug interactions Anticholinergics increase bioavailability Mg salts decrease absorption Uricosurics (probenecid) increase serum levels Patient education GI upset  may take with food or milk Brown discoloration of urine Notify HCP if: Fever, chills, cough, chest pain, difficulty breathing, skin rash, numbness or tingling of fingers or toes, intolerable GI upset

Drug interactions

Anticholinergics increase bioavailability

Mg salts decrease absorption

Uricosurics (probenecid) increase serum levels

Patient education

GI upset  may take with food or milk

Brown discoloration of urine

Notify HCP if:

Fever, chills, cough, chest pain, difficulty breathing, skin rash, numbness or tingling of fingers or toes, intolerable GI upset

Fosfomycin (Monurol) Indication UTI Patient variables Pediatrics: contraindicated in children Pregnancy: Category B Lactation: Use NOT recommended Adverse effects Diarrhea, nausea, dyspepsia, vaginitis, headache, dizziness, asthenia (muscle weakness) Drug interactions Serum levels lowered by drugs that slow GI motility

Indication

UTI

Patient variables

Pediatrics: contraindicated in children

Pregnancy: Category B

Lactation: Use NOT recommended

Adverse effects

Diarrhea, nausea, dyspepsia, vaginitis, headache, dizziness, asthenia (muscle weakness)

Drug interactions

Serum levels lowered by drugs that slow GI motility

Metronidazole (Flagyl) Indications Short-acting synthetic antiprotozoal & antibacterial Active against most anaerobic bacteria, certain protozoa, and H. pylori Outpatient: most often used to Tx T. vaginalis and non-specific BV Excellent tissue penetration  used in Tx of many pelvic & intra-abdominal infections Can lower potential for overgrowth of C. difficile associated with certain antibiotics Mechanism of action Cytotoxic BUT mechanism NOT well understood  directly damages DNA synthesis  cell death

Indications

Short-acting synthetic antiprotozoal & antibacterial

Active against most anaerobic bacteria, certain protozoa, and H. pylori

Outpatient: most often used to Tx T. vaginalis and non-specific BV

Excellent tissue penetration  used in Tx of many pelvic & intra-abdominal infections

Can lower potential for overgrowth of C. difficile associated with certain antibiotics

Mechanism of action

Cytotoxic BUT mechanism NOT well understood  directly damages DNA synthesis  cell death

Metronidazole (Flagyl) Drug Tx principles Excellent activity against G(-) & G(+) anaerobes Indicated for use in serious infections Reaches high concentrations in most body tissues Does NOT cover G(+) cocci or aerobic organisms Primary care: drug of choice for Trichomonas vaginalis (both partners require Tx) & bacterial or non-specific vaginitis Tx of choice for symptomatic Giardia Recommended initial Tx for C. difficile (vanco for severe cases) Tx for H. pylori in gastritis & PUD in conjunction with bismuth & tetracycline

Drug Tx principles

Excellent activity against G(-) & G(+) anaerobes

Indicated for use in serious infections

Reaches high concentrations in most body tissues

Does NOT cover G(+) cocci or aerobic organisms

Primary care: drug of choice for Trichomonas vaginalis (both partners require Tx) & bacterial or non-specific vaginitis

Tx of choice for symptomatic Giardia

Recommended initial Tx for C. difficile (vanco for severe cases)

Tx for H. pylori in gastritis & PUD in conjunction with bismuth & tetracycline

Metronidazole (Flagyl) Pharmacokinetics Absorption Well absorbed; peak 1-2 hr; ½ life 8 hrs Food does NOT alter bioavailability BUT can delay peak Plasma concentration proportional to administered dose Distribution Large Vd; 20% protein binding Reaches all body tissues & fluids including: bone, pelvic tissue, CSF, meninges, bile, saliva, seminal fluid, breast milk, placenta, abscesses (including brain & hepatic), empyema fluid, middle ear fluid Metabolism Liver; plasma clearance decreased in liver dysfunction Excretion Urine; accumulation in renal failure BUT rarely toxic

Pharmacokinetics

Absorption

Well absorbed; peak 1-2 hr; ½ life 8 hrs

Food does NOT alter bioavailability BUT can delay peak

Plasma concentration proportional to administered dose

Distribution

Large Vd; 20% protein binding

Reaches all body tissues & fluids including: bone, pelvic tissue, CSF, meninges, bile, saliva, seminal fluid, breast milk, placenta, abscesses (including brain & hepatic), empyema fluid, middle ear fluid

Metabolism

Liver; plasma clearance decreased in liver dysfunction

Excretion

Urine; accumulation in renal failure BUT rarely toxic

Metronidazole (Flagyl) Contraindications Avoid ALL alcohol  antabuse or disulfuram-like reaction Hypersensitivity Warnings/Precautions CNS disease: seizures & peripheral neuropathy reported Hepatic disease: accumulation of drug & metabolites  dose reduction required with impairment Crohn’s: increased GI cancers Hx blood dyscrasias: can induce mild leukopenia Carcinogenesis in rodents with chronic oral administration

Contraindications

Avoid ALL alcohol  antabuse or disulfuram-like reaction

Hypersensitivity

Warnings/Precautions

CNS disease: seizures & peripheral neuropathy reported

Hepatic disease: accumulation of drug & metabolites  dose reduction required with impairment

Crohn’s: increased GI cancers

Hx blood dyscrasias: can induce mild leukopenia

Carcinogenesis in rodents with chronic oral administration

Metronidazole (Flagyl) Patient variables Geriatrics Altered pharmacokinetics – monitor serum levels Pediatrics S&E NOT established in children except for Tx of amebiasis Pregnancy Category C Crosses placenta & enters fetal circulation Lactation Found in breast milk Safety in nursing NOT established

Patient variables

Geriatrics

Altered pharmacokinetics – monitor serum levels

Pediatrics

S&E NOT established in children except for Tx of amebiasis

Pregnancy

Category C

Crosses placenta & enters fetal circulation

Lactation

Found in breast milk

Safety in nursing NOT established

Metronidazole (Flagyl) Adverse effects MOST COMMON: GI  nausea, vomiting, diarrhea, epigastric discomfort Also: Metallic taste, dizziness, headache, dysuria, vaginal dryness, dark urine Less common BUT SERIOUS: seizures, ataxia, peripheral neuropathy Drug interactions Disulfuram-like reaction with alcohol (immediate n/v/d & CV effects) Patient education GI upset, darkens urine, metallic taste Avoid alcohol Trichomoniasis is STI  need to Tx both partners for cure Finish all medication – do NOT share medication with others

Adverse effects

MOST COMMON: GI  nausea, vomiting, diarrhea, epigastric discomfort

Also: Metallic taste, dizziness, headache, dysuria, vaginal dryness, dark urine

Less common BUT SERIOUS: seizures, ataxia, peripheral neuropathy

Drug interactions

Disulfuram-like reaction with alcohol (immediate n/v/d & CV effects)

Patient education

GI upset, darkens urine, metallic taste

Avoid alcohol

Trichomoniasis is STI  need to Tx both partners for cure

Finish all medication – do NOT share medication with others

Chloroquine (Plaquenil) Indications Prophylaxis & Tx of acute attacks of malaria Also: rheumatoid, SLE, scleroderma Mechanism of action Unknown – raises internal pH of parasites; may interfere with Hgb digestion or nucleoprotein synthesis Contraindications Hypersensitivity Retinal or visual changes

Indications

Prophylaxis & Tx of acute attacks of malaria

Also: rheumatoid, SLE, scleroderma

Mechanism of action

Unknown – raises internal pH of parasites; may interfere with Hgb digestion or nucleoprotein synthesis

Contraindications

Hypersensitivity

Retinal or visual changes

Chloroquine (Plaquenil) Warnings/Precautions Resistance Irreversible retinal damage  monitor vision frequently Patient variables Pediatric: sensitive  fatalities have occurred Pregnancy: only if clearly indicated Lactation: safety NOT established Monitoring Periodic CBC for blood disorders Adverse effects SEVERE: CV, ophthalmic retinal damage, agranulocytosis

Warnings/Precautions

Resistance

Irreversible retinal damage  monitor vision frequently

Patient variables

Pediatric: sensitive  fatalities have occurred

Pregnancy: only if clearly indicated

Lactation: safety NOT established

Monitoring

Periodic CBC for blood disorders

Adverse effects

SEVERE: CV, ophthalmic retinal damage, agranulocytosis

Chloroquine (Plaquenil) Overdosage Headache, drowsiness, visual disturbances, CV collapse, convulsions, death Tx symptomatic Drug interactions Cimetidine reduces clearance Patient eduation GI upset  take with food Report: Visual disturbances, difficulty hearing or ringing in ears, diarrhea, vomiting, muscle weakness, or rash

Overdosage

Headache, drowsiness, visual disturbances, CV collapse, convulsions, death

Tx symptomatic

Drug interactions

Cimetidine reduces clearance

Patient eduation

GI upset  take with food

Report:

Visual disturbances, difficulty hearing or ringing in ears, diarrhea, vomiting, muscle weakness, or rash

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