Antiprotozoal drugs - Classification, Mechanism of action and therapeutic uses

1. Antiamoebic and Other
Antiprotozoal Drugs
Dr. Netravathi
Associate Professor
J. N. Medical College
Belagavi

5. Antiamoebic Drugs

6. Metronidazole
• It is the prototype nitroimidazole
• It has broad spectrum cidal- anaerobic protozoa &
Giardia lamblia
• Many anaerobic and microaerophilic bacteria
Bact. fragilis,
Fusobacterium
Clostridium perfringens
Cl. difficile,
Helico bacter pylori
Campylobacter
Peptococci
spirochetes and anaerobic Streptococci
Aerobic
bacteria
X

7. Metronidazole- Mechanism of action

8. Pharmacokinetics
 Oral or IV.
 Is completely and rapidly absorbed after oral
administration
 It distributes well in body tissues and appears in body
fluids. saliva, breast milk
 Metabolized in liver by oxidases followed by
glucuronidation
 Excreted in urine(red color)
 Clearance is decreased in liver impairment

9. Uses of Metronidazole
• Amoebiasis: Invasive dysentry -800mg TDS 7-10 days
• Liver abscess- 500mg TDS 7-10 days(iv)
• Mild intestinal disease- 400mg TDS 5-7days
• Giardiasis- 400mg TDS -7days
• Trichomonas vaginitis- 2gm single dose
• Anaerobic bacterial infections- iv/Oral

10. Uses of metronidazole
• Pseudomembranous enterocolitis- 800mg TDS 10-14 days
• Ulcerative gingivitis/ Trench mouth(ANUG)- 400mg TDS
5-7days along with amoxycillin
• H.pylori gastritis/peptic ulcer- 400mg TDS 5-7days
• Guinea worm infestation

11. Adverse effects of Metronidazole

12. Tinidazole
Advantages over metronidazole:
Metabolism is slower – Plasma half life – 12
hours. Single dose or once daily therapy.
Higher cure rates than Metronidazole in
amoebiasis.
Better tolerated.

13. Uses of Tinidazole
• Trichomoniasis and Giardiasis: 2g single
dose.
• Intestinal amoebiasis: 2g OD for 3 days.
• Amoebic liver abscess: 2g OD for 3 -6
days.

14. Uses of Tinidazole
H plori eradication: 500mg BD for 2
weeks.
Anaerobic infections:
Prophylactic: 2g single dose before
colorectal/biliary surgery.
Therapeutic: 2g followed by 0.5g BD for
5days.

15. Choloroquine
• Direct toxicity to trophozoites.
• Used when nitroimidazoles C/I or not available.
• Indication: Amoebic liver abscess along with
luminal agent.
• Dose: 600mg (base) for 2 days
followed by 300mg daily for 2-3 weeks.

16. Luminal Amoebicides
Diloxanide furoate
• It is a highly effective luminal amoebicide which
directly kills trophozoites
• single course produces high (80–90%) cure rate
in mild intestinal amoebiasis and in
asymptomatic cyst passers.
• 500 mg TID for 5- 10 days

17. 8 Hydroxyquinolones (Clioquinol,
Iodoquinol)
• Iodoquinol – safer of the two.
• Clioquinol – subacute myelo-optic neuropathy.
• Iodoquinol – High doses – Children – optic
atrophy & permanent blindness.
• Indication: Iodoquinol with metronidazole –
amebic colitis
• Single agent: Asymptomatic individuals.

18. Nitazoxanide
• Broad spectrum antiparastic
agent.
• Salicylamide congener of
niclosamide.
• MOA: Tizoxanide: Inhibits PFOR
enzyme dependent electron
transfer reaction.

19. Uses of nitazoxanide
• Giardia intestinalis infection and diarrhoea
caused by cryptosporidia: 500mg every 12
hours.
• Mixed infections with intestinal parasites
(protozoa and helminths).
• Fasciola hepatica infection

20. Paromomycin
• Aminoglycoside
• Amoebic liver abscess and amoebic colitis.
• Giardiasis in first trimester of pregnancy.
• 6.25% cream – Vaginal trichomoniasis.
• Topical formulation: Cutaneous leishmaniasis.
• Parenterally alone or combination with antimony:
Visceral leishmaniasis.

21. Pharmacotherapy of amoebiasis
• Acute amoebic dysentery

22. Pharmacotherapy of amoebiasis

23. Pharmacotherapy of amoebiasis

24. Giardiasis

25. Drugs for giardiasis
• Nitroimidazoles
• Nitazoxanide
• Quinidochlor
• Furazolidine

26. Treatment regimens for giardiasis
• Metronidazole: 2g daily for 3 days.
• Secnidazole/Tinidazole: 2g single dose.
• Nitazoxanide: 500mg BD for weeks.
• Quiniodochlor: 250mg TDS for 7 days.
• Furazolidine: 100mg TDS for 5-7 days.

27. Drugs for Trichomoniasis
• Trichomonas vaginalis- Vulvovaginitis
• Drugs used orally
• Drugs used intravaginally

28. Drugs used orally:
Metronidazole: 400mg TDS for 7 days or 2g
single dose.
Tinidazole/Secnidazole: 2g single dose.
Drugs used vaginally:
Diiodohydroxyquin: (Pessary): 200mg inserted
intravaginally at bedtime – 1-2 weeks.
Quiniodochlor: (Vaginal tab): 200mg – 1-3
weeks.
Povidone iodine: (Pessary): 400mg – 2 weeks.

29. Drugs for Leishmaniasis

30. Recommended treatment regimens for visceral
leishmaniasis (Kala-azar)
1. Amphotericin B deoxycholate (AMB-DOC): 0.75–1.0 mg/kg i.v.
infusion over 4 hours daily or on alternate days till 15 mg/kg total
dose.
2. Liposomal amphotericin B (L-AMB): 3–5 mg/kg i.v. infusion daily for
3–5 days (total dose 15 mg/kg
3. Miltefosine (all doses given orally with meals for 28 days)
Adults (>12 years) weighing > 25 kg: 100 mg/day
4. Paromomycin sulfate: 15 mg (11 mg base) per kg/day i.m. for 21
days

31. COMBINATIONS (co-administered drugs)
1. L-AMB (5 mg/kg i.v. infusion single dose) + Miltefosine
(as above) for 7 days.
2. L-AMB (5 mg/kg i.v. infusion single dose) +
Paromomycin (as above) for 10 days.
3. Miltefosine (as above) daily for 10 days + Paromomycin
(as above) daily for 10 days.