Post on 03-Apr-2018
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Antiparasitic AgentsMa. Victoria M. Villarica RN, MD, FPSECP
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Objective
•
Differentiate protozoal and helminthic infections• Discuss conditions that promote parasitic infections
• Discuss the kinetics and dynamics of antiparasitic agents
• Enumerate the drug of choice for the different parasiticinfections
• Learn to manage parasitic infections
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Principles of Treatment:
1. Protozoal infections are always treated.2. Helminthic infection therapy depends on:
a. number and life span of worms harbored by
the patient
b. likelihood and seriousness of persons and
public health complicationsc. availability and efficacy of therapeutic agents
3. Individualized treatment
4. Ff-up clinical and laboratory assessment is
needed5. Patient education is a must.
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Conditions promoting parasitic infections:
1. Poor sanitation, personal hygiene and health education
2. Debilitation and compromised resistance of the host
3. High population density
4. Inadequate control of parasite vectors and reservoirs of
infection
5. Increase population migration
6. Military operations
7. Resistance
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3 Major types of potential targets for chemotherapy of parasitic
disease:
- rational approach is to target metabolic pathway that represents points
of vulnerability
1. Unique enzymes found only in the parasite - limited use
because of development of resistance
2. Enzymes indispensable only in the parasite - essential for
survival of the parasite
3. Common indispensable biochemical functions with
different pharmacologic properties - found both on the
human host and the parasite but would target only the
parasite
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Targets of antiparasitic
chemotherapy
• Unique enzymes found only in the parasite
- pyruvate phosphate dikinase –
main source of energy of entamoebas (glycolysis)
• Indispensable enzymes
- lanosterol demethylase is required for ergosterol synthesis
in leishmanias• Common indispensable biochemical functions
- microtubules in ascaris and human host
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Parasitic infections:
a. protozoa
1. Sarcodina - amoebas
2. Sporozoans – plasmodium, toxoplasma,
cryptosporidium
3. Flagellates – trichomonas, giardia, trypanosoma,
leishmania, pneumocystosis
4. Ciliates – Balantidium coli
b. metazoa
1. Cestoda - tapeworms
2. Trematoda - flukes
3. Nematoda – roundworms, pinworms, etc
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Antiprotozoal Agents
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Sporozoans
Malaria:
• 4 species of plasmodium cause human malaria
(P. falcifarum, P. vivax, P. malariae, P. ovale;
P. knowlesi)
• life cycle: liver/tissue phase and blood phase
• radical cure - eliminate both hepatic and erythrocytic stages; no such
drug
• suppressive cure - complete elimination of parasite from the body by
continued therapy
• clinical cure - terminate clinical attack
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Diagnosis of malaria
• Direct microscopy – less expensive but skilled staff is
needed
• RDT (rapid diagnostic test) - expensive
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1. Tissue schizonticide - eliminate developing or dormant
liver forms
a. Primaquine
2. Blood schizonticide - act on erythrocytic parasite
a. Chloroquine
b. Quinine
c. Mefloquine
d. Inhibitors of folate synthesis
e. Tetracycline, Doxycycline, Clindamycin
f. Halofantine
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3. Gameticide - kill sexual stages
a. Quinine
b. Primaquine
4. Causal prophylactic drugs - capable of preventing
erythrocytic infection
a. Chloroquine
b. Mefloquine
c. Inhibitors of folate synthesis
d. Doxycycline, Azithromycin
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Antimalarial Agents:
I. Chloroquine - drug of choice for both treatment and
chemoprophylaxis of sensitive P. falcifarum and other
species
• act by concentrating in parasite food vacoules,
preventing the polymerization of the hgb breakdownproduct, heme, into hemozoin and thus eliciting
parasite toxicity due to build-up of free heme.
• Resistance is due to mutations in a putative
transporter/decreased carrier-mediated transport
• Safe in pregnancy and young children
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Chloroquine
Adverse effect: GI upset, mild headache, visual disturbances, urticaria
- 5 gm. Fatal
Availability: Aralen 250mg tablet (150mg base)
Not given IV: cardiotoxicity
Dose: adult: 1 gm ffed by 500mg at 6hrs., 24 hrs. and 48hrs.
Or
1 gm at 0 , 24hrs then 500mg at 48hrs.
child: 10mg/kg initially then 5mg/kg at 6hrs. ,24 hrs. and 48 hrs.
(for P. vivax: ffed by: Primaquine 0.3mg/kg once a day x 14days)
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II. Amodiaquine- same mechanism of action as Chloroquine (not available in the Phils)
• low cost; limited toxicity; effective against chloroquine-resistant
strains in certain areas
• Tx for chloroquine resistant strains of P. falcifarum
• Not for chemoprophylaxis
• AE: agranulocytosis
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III. Quinine•
Used for treatment of severe Falcifarum malaria and chloroquineresistant strains
• MOA: inhibits plasmodium hgb polymerase
• AE: cinchonism, hemolytic anemia, blackwater fever
Preparation: 300mg (350mg base) tablet
300mg/l ampule
Dose: child: 25 mg (8.33mg base)/kg/day in
3 doses x 3-7 days
adult: 600 mg TID x 3-7 days
IV: 20mg/kg loading dose over 4 hrs. ffed by
10mg/kg IV over 2-4hrs. every 8hrs. until
oral therapy can be started
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CNS or complicated malaria
Quinidine 10mg/kg IV for 1-2hrs ffed by 0.02mg/kg or
15mg/kg IV in 4 hrs. ffed
by 7.5mg/kg in 4 hrs. every 8hrs.OR
Artesunate 2.4mg/kg IV or IM then 1.2mg/kg every 12hrs. for 1
day, then everyday
OR
Artemether 3.2mg/kg IM then 1.6mg/kg/day everyday IM
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IV. Melfloquine - chemically related to Quinine
- chemoprophylaxis and blood schizonticide for chloroquine-resistant
strains of P. falcifarum
- given only orally; severe local irritations
- MOA: swelling of parasitic food vacuoles
- considered safe for young children; safe in pregnancy but limitedexperience in 1st trimester
- AE: confusion, psychosis (lessened by splitting the dose)- Availability: Lariam 250 mg tab- Dose: (treatment)
adult: 750 mg then 500mg in 6-8hrs.
child: 15mg/kg single dose
(prophylaxis):250 mg weekly (1 week before and 4 weeks after)
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Mefloquine
• 2002 –
reported murders and suicides among US soldiersat Fort Bragg, N.C., given Lariam while stationed in war
zones
• March 5, 2009 Jeff Schogol, Arlington, Va
- C/I in patients with depression, traumatic brain injury,convulsions
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V. Primaquine- drug of choice for the eradication of dormant liver forms
of P. vivax and ovale- MOA: : - unknown mechanism of action
- swelling of parasitic food vacuoles
- gametocidal (4 strains)- check G6PD status- not used as standard treatment; oral- C/I: pregnancy- Other uses: pneumocystis carinii infection
- AE: hemolytic anemia- Dose: 26.3mg (15mg base)/kg once a day x 14 days
- preparation: Primaquine 15mg tab (US)
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VI. Inhibitors of folate synthesis
- selectively inhibit plasmodial dihydrofolate reductase, a
key enzyme in the pathway for the synthesis of folate
- resistance is due to mutations in dihydrofolate
reductase and dihydropterase synthase
1. Pyrimethamine (Fansidar)- safe in pregnancy,
chemoprophylaxis; toxoplasmosis, pneumocystosis
2. Proguanil (Chloroguanide)- safe in pregnancy; for
treatment and prophylaxis (safe alternative to
mefloquine; (+) chloroquine 500mg weekly and
proguanil 200mg daily
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1. Pyrimethamine (Fansidar)
- safe in pregnancy, chemoprophylaxis;
- toxoplasmosis, pneumocystosis
- MOA: inhibit dihydropteroate synthase (failure of nuclear division)
- synergism (sulfonamides)
- not recommended for chemoprophylaxis because of toxicity (once weekly)- Dose: adult: 2 tabs. Single dose
child: 1.25mg pyrimethamine/kg and 25mg sulfa/kg 0R
sulfadoxine-pyrimethamine
4 yrs. – ½ tab ; 4-8yrs. – 1 tab;
9-14yrs. –
2 tabs; > 14yrs. –
2-3 tabs.- Preparation: 500mg sulfadoxine + 25mg pyrimethamine tablet
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2. Proguanil
- safe in pregnancy; for treatment and prophylaxis (safe
alternative to mefloquine);
- (+) chloroquine 500mg weekly and proguanil 200mg daily
- Ineffective against resistant strains
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VII. Antibiotics - Unclear mechanism of action (inhibits cell wall
synthesis)
- Tetracycline (for malaria, intestinal amoebiasis),20mg/kg/day in 4 doses (max. 250mg QID) x 7days(treatment)
preparation: 250mg and 500mg caps.- Doxycycline (chemoprophylaxis in SE Asia;for tx: (+quinidine or quinine) 100mg BID x 7days
prophylaxis: 100mg daily 2 days before and 1 week after departure from endemic area
- Clindamycin (malaria, toxoplasmosis, pneumocystosis, babesiosis) (treatment): 600 mg BID x 7days - Azithromycin
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VIII. Halofantrine
- limited use because of irregular absorption and cardiac
toxicity
- C/I: pregnancy
- dose: (treatment)
>40kg: 2 – 250mg at 6-hrs interval (6 tabs) or
<40kg. 24mg/kg divided in 3doses at 6 hrs. interval
- preparation: (not available in the Phils)
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IX. Artemisinin and derivatives
- only drug reliably effective against quinine-resistant strains
- production of free radicals; best given with doxycycline or
Fansidar - C/I: pregnancy
- Quinghaosu- insoluble and can only be used orally
- preparation: 20mg artemether + 120mg lumefantrin tab.
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Artemisinin and derivatives
• Artemether + Lumefantrine (AL) –
BID X 3days
•
Artesunate + Amodiaquine (AS+AQ) –
OD X 3 days
• Artesunate + mefloquine (AS + MQ) –
OD X 3 days
• Artesunate + Sulfadoxine-Pyrimethamine (AS + SP) – OD X 3 days
• Dihydroartemisinin + Piperaquine (DHA + PPQ) - OD X 3 days
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X. Malarone
• Atovaquone + proguanil
• Alternative therapy to P. carinii (750mg TID with meals X 21days)
• Dose: 4 tabs. Daily x 3 days (treatment)
250 mg tab (prophylaxis)
• Preparation: 250mg/100mg tab
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WHO 2010 Guidelines for the
Treatment of Malaria
• Tx for uncomplicated malaria:
• Dihydroartemisinin + Piperaquine (DHA + PPQ) - OD X 3 days –
first line; strong recommendation; high quality of evidence
• Artemether + Lumefantrine (AL) – BID X 3days
• Artesunate + Amodiaquine (AS+AQ) – OD X 3 days
• Artesunate + mefloquine (AS + MQ) – OD X 3 days
• Artesunate + Sulfadoxine-Pyrimethamine (AS + SP) – OD X 3 days
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Treatment for uncomplicated
P. vivax malaria
• Choloroquine + Primaquine
• ACT (except AS + SP) + Primaquine
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Treatment of Malariaduring Pregnancy
• 1st trimester
- Quinine + Clindamycin X 7 days
- Artesunate + Clindamycin X 7 days
ACT X 3 days
• 2nd trimester
- ACTSP X 3 days
- AS + Clindamycin X 7 days
- Quinine + Clindamycin X 7 days
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2nd line antimalarialagents
•Artesunate (OD) + Tetracycline (QID) or Doxycycline(OD) or Clindamycin (BID)
X 7 days
• Quinine + Tetracycline (QID) or Doxycycline (OD) or
Clindamycin (BID)X 7 days
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Pneumocystis pneumonia
Trimethoprim + Sulfamethoxazole
Use: Pneumocystis jirovecii (carinii) pneumonia
chemoprophylaxis: 1 (160 mg) tab OD or 3x/week
treatment: 2 (160mg) tabs every 8 hrs. x 21 days
Preparation: - 40mg/80mg trimetoprim +
200mg/400mg sulfamethoxazole susp.
- 80mg/160mg trimetoprim tab. +
400mg/800mg sulfamethoxazole tab.
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Amoeba Life Cycle:
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Drugs used for Amoebiasis
Classification:
I. Tissue amoebicidea. Dehydroemetine, Emetine
b. Chloroquine
II. Luminal amoebicide
a. Halogenated hydroxyquinolines
1. Diiodohydroxyquin
2. Iodochlorhydroxyquin
3. Dibromohydroxyquinoline
b. Dichloroacetamide
1. Diloxanide furoate
2. Clefamide
3. Teclozan
4. Etofamide
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c. Antibiotic
1. Paramomycin
III. Tissue and Luminal amoebic
a. Nitroimidazole
1. Metronidazole
2. Tinidazole
3. Ornidazole
4. Secnidazole
b. Niridazole
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Amebicidal Agents:
I. Metronidazole - drug of choice for the treatment of
extraluminal amebiasis
- kills trophozoites but not cysts
- nitro group of metronidazole is chemically reduced in
anaerobic bacteria and sensitive protozoas
- DOC: tissue amoebiasis, giardiasis, trichomoniasis (2 g. SD)
- AE: nausea, headache, dry mouth, metallic taste,
disulfiram-effect
- Drug interaction: anticoagulants, phenytoin, phenobarbital
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II. Iodoquinol - effective luminal amoebicide
- unknown mechanism of actionIII. Diloxanide furoate - drug of choice for asymptomatic
luminal infections
- unknown mechanism of action
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IV. Paramomycin sulfate - an aminoglycoside used only
as a luminal amebicide
Availability: 250 mg caps. (US)
V. Emetine and Dihydroemetine - has limited use, given
SC or IM, not IV x 3-5 days
- analog derived from ipecac
AE: pain and tenderness; diarrhea, nausea and
vomiting
C/I: patients with cardiac or renal disease; children and
pregnancy
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Other Protozoal Agents:
I. Pentamidine - only administered parenterally (IV and
aerosol)
- used in Pneumocystosis (aerosol): once a month
(prophylaxis)
IV or IM: OD x 21 days (treatment)
African Trypanosomiasis, Leishmaniasis
- unknown mechanism of action (interferes with nucleic acidmetabolism of protozoas)
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anemia
enlarged liver and spleenfever
weaker inflammatory response (due to the
loss of phagocytes)
weight loss.
cutaneous leishmaniasis
visceral leishmaniasis
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II. Sodium Stibogluconate
- 1st line agents against cutaneous and visceral Leishmaniasis- unknown mechanism of action
- dose: 20mg/kg/day IV or IM x 20 days
- AE: GI upsets, sterile abscess
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III. Drugs for Trypanosomiasis
a. Suramin - for African trypanosomiasis,but do not
enter the CNS
- unknown mechanism of action
- dose: 200mg IM test dose; 1g on days 1,3,7,14,21
b. Melarsoprol - 1st line therapy for advanced CNS
African Trypanosomiasis
- dose: 3.6mg/kg/day x 3-4days
c. Eflornithine - an inhibitor of ornithine decarboxylase
- a 2nd therapy for advanced CNS African trypanosomiasis
- dose: 100mg/kg IV every 6hrs. X 14 days ffed by oral
therapy for 3-4weeks
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d. Nifurtimox - most common drug used for American
Trypanosomiasis (Chagas disease)
dose: 8-10mg/kg orally x 3-4months
e. Benznidazole - for the treatment of acute Chagas disease
toxicities: peripheral neuropathy, rash, GI symptoms,myelosupression
.
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Antihelminthic Agents
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Enterobius vermicularisAscaris lumbricoides
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Rectal prolapse in
Trichuris trichiuria
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“pinworm/treadworm/seatworm”
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Antihelminthic Drugs: I. Albendazole - drug of choice for the treatment of hydatid
disease, neurocysticercosis and cutaneous larva migrans
MOA: act by inhibiting microtubule synthesis in nematodes,
thus irreversibly impairing glucose uptake; also has
larvicidal effects in hydatid disease, cysticercosis,
ascariasis and hookworm infection and ovicidal effects in
ascariasis, ancylostomiasis and trichuriasis
Availability: Zentel 400mg tab and 200mg/5ml
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Albendazole
Roundworms, pinworm, hookworm:
400mg SD may repeat in 3wksStrongyloidiasis, taeniasis:
400mg daily x 3 days (may rpt)
Larval taeniasis:
800mg in 2 divided doses x 14-30days Neurocysticercosis: 15mg/kg OD x 8-30days
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“whipworm”
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II. Mebendazole - same MOA as Albendazole
- used in ascariasis, trichuriasis and hookworm and
pinworm infection
- MOA: act by inhibiting microtubule synthesis in
nematodes, thus irreversibly impairing glucoseuptake; also has larvicidal effects in hydatid
disease, cysticercosis, ascariasis and
hookworm infection and ovicidal effects in
ascariasis, ancylostomiasis and trichuriasis
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Mebendazole
Availability: Antiox 100mg, 500mg tab
50mg/ml and 100mg/mlAscariasis, Trichuriasis, Hookworm:
1-day treatment (500mg SD)
3-day treatment (100mg/day or
100mg BIDx 3days)Enterobiasis:
100mg SD, repeated after 2 weeks
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III. Thiabendazole- alternative drug for the treatment of strongyloidiasis and
cutaneous larva migrans
- same MOA as Albendazole
- a chelating agent
- has anti-inflammatory properties, has immunomodulatingeffects on T cell function
Cream: 2-3x a day x 5 days
Trichinosis: 25mg/kg BID x 7 days
Strongyloidiasis:25mg/kg in 3 divided doses x 2 days
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IV. Bithionol
- drug of choice for the treatment of fascioliasis
- dose: 30-50mg/kg in 2-3divided doses, orally, after meals onalternate days x 10-15days
- AE: abdominal cramps; caution in children
- an alternative drug in the treatment of pulmonary
paragonimiasis
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V. Diethylcarbamazine Citrate- drug of choice for the treatment of filariasis, Loiasis and tropial eosinophilia
- MOA: immobilizes the microfilariae and alters their surface structure,making them more susceptible to destruction by host defense mechanism
- mazzoti reaction (give antihistamines)
- Mass treatment: 6mg/kg weekly every 6-12 mos.
- Treatment: 2mg/kg 3x a day x 7 days (lymphatic filariasis) repeated after 3-4 weeks
- Prophylaxis: 50mg monthly (lymphatic filariasis)
- Treatment: 1mg/kg daily x 3 days then
8-10mg/kg x 2-3weeks (loa-loa)- Prophylaxis: 300mg weekly (loa-loa)
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I. Emetine Hydrochloride
- are alternative drugs for the treatment of Fasciola hepatica
infection.
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VII. Ivermectin
- drug of choice in strongyloidiasis and onchocercosis- an alternative drug for scabies and filariasis
- no known pharmacologic or toxic effects in humans because it doesnot cross the blood brain barrier
- MOA: modulates GABA-mediated neurotransmission
- AE: mazzoti reaction- Dose: onchocercosis: 150ug/kg with water, 3 mos. interval x 12 mos.
strongyloidiasis: 200ug/kg SD
Bancroftian filariasis: 400ug/kg + diethylcarbamazine 6mg/kg
scabies
- C/I: children younger than 5 years of age or to those weighing lessthan 15 kg; to pregnant women; or to nursing mothers in the infant'sfirst week of life.
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VIII. Levamisole
- highly effective in eradicating ascaris
and trichostrongylus and moderately
effective against both species of
hookworm (repeat tx once in 3-7days)
- dose: 150mg SD
- used as an immunomodulating agent as adjunct therapy withfluoroucil after surgical resection in patients with Duke stage
C colon cancer.
IX Metrifonate f l t lt ti d f th
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IX. Metrifonate - a safe, low cost alternative drug for the
treatment of Schistosoma haematobium infections
- MOA: cholinesterase inhibition- dose: 7.5-10mg/kg orally TID SD at 14days interval
X. Niclosamide - drug of choice for most tapeworm
infections, but not available in the US
- MOA: inhibition of oxidative phosphorylation or to its
ATPasestimulating property.
- dose: 2 g. (4tabs) SD chewed then swallowed with
water
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II. Oxantel Pamoate/Pyrantel Pamoate
- MOA: depolarizing muscular blocking (Ach) agents (pyrantel:
ascaris and hookworm
oxantel: trichuriasis
- dose: roundworm, pinworm,
trichostrongyliasis: 11mg/kg SD
hookworm: 11mg/kg/day OD x 3 days
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XIII. Piperazine citrate - alternative drug in the treatment
of ascariasis
- almost free of pharmacologic action in the host
- MOA: causes paralysis of ascaris by blocking
acetylcholine at the myoneural junction
- dose: ascariasis: 75mg/kg/day OD x 2days
enterobiasis: 65mg/kg/day OD x 7days
- preparation: 500mg/5 ml and 1 g/5ml
- AE: seizures
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XIV. Praziquantel
- effective in the treatment of schistosome infection of all speciesand most other
trematode and cestode infections, including cysticercosis
- MOA: drug increases cell membrane permeability to calcium,resulting vacuolization, marked contraction,
paralysis, dislodgement, and death
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Praziquantel
• Dose: schistosomiasis: 40mg/kg/dose BID x 1 day at
4-6hrs. intervalflukes: 25mg/kg/dose every 8hrs. X 1-2days
tapeworms: 5-10mg/kg SD
cysticercosis: 15.5mg/kg/dose every 8hrs.
X 15days• Preparation: 600mg tab
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Integrated Management of
Childhood Illness (2008)
• Deworming – 12-59 months old: Mebendazole 500 mg
single dose OR
Albendazole 400 mg single dose
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In summary …..
• Differentiate protozoal and helminthic infections
• Discuss conditions that promote parasitic infections
• Discuss the kinetics and dynamics of antiparasitic agents
• Enumerate the drug of choice for the different parasiticinfections
• Able to manage parasitic infections
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(Boracay!!)
Thanks dami
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