antiamoebic drugs

1. Antiamoebic drugs
classification
1.Tissue amoebicides
a. For both intestinal and extraintestinal amoebiasis:
Metronidazole,tinidazole,secnidazole,ornidazole
b. For extraintestinal amoebiasis only: chloroquine
2.Luminal amoebicides
a) Amide- diloxanide furoate,nitazoxanide
b) 8-hydroxyquinolines- quiniodochlor
c) Antibiotic - tetracyclines

2. metronidazole
• Antiprotozoal(against amoeba,giardia,trichomonas vaginalis)
• Antibiotic(against anaerobic bacteria-bacteroids fragilis,clostridium
difficile,clostridium perfringes,fusobacterium)
• Not effective against aerobic bacteria.
• MOA- nitro group of metronidazole
reactive nitro radical
cytotoxicity
• A/E -1.metallic taste,nausea,abdominal cramps,anorexia
2.less common-headache,glossitis,dryness of mouth
• C/I- 1.neurological disease
2.blood dyscrasias
3.first trimester of pregnancy
4.chronic alcoholism(a disulfiram like intolerance to alcohol occurs in
some patients)

3. uses
1. Amoebisis-400mg tds for 5-7 days(liver abscess-800mg tds for 7-
10days)
2. Giardiasis
3. Trichomonas vaginitis
4. Anaerobic bacterial infections
5. Pseudomembranous enterocolitis
6. Ulcerative gingivitis,trench mouth
7. Helicobacter pylori gastritis/peptic ulcer
preparations-metrozyl,metron,flazyl 200mg 400mg tab 200mg/5mlsusp
500mg /1ooml iv infusion

4. Tinidazole
• Similar to metronidazole in every way except:
• Metabolis is slower,t1/2-12 hour,duration-longer less frequent dosing
• Amoebiasis-2g od *3 days or o.6gm bd *5-10 days
• Trichomoniasis and giardiasis-2g single dose or 0.6 g od for 7 days.
• Preparations- tiniba 300 500 1000 mg tab 800mg/400ml iv infusion
• Higher cure rates ,better tolerated and lesser side effects
Secnidazole
• same activity and potency as metronidazole,t1/2 -24 hour
• Dose-2g single dose(amoebiasis,giardiasis,trichomoniasis),1.5 gm/day for hepatic
amoebiasis
Ornidazole
• activity similar to metronidazole,dose and duration similar to tinidazole
• Preparation-ornida 5oomg tab,125mg/5ml syp.

5. Diloxanide furoate
• Luminal amoebicide directly kills trophozoite,its anti-amoebic activity
is due to furate ester which is released after hydrolysis in intestine.
• No anti-bacterial action and less effective in invasive amoebiasis.
• Dose-500mg tds for 5-10 days.
• Preparations-furamide o.5 gm tab;generally comes in combination
with metronidazole or tinidazole[metron-df 400mg +500mg,tiniba-df
forte 500mg +300 mg]
• S/E- flatulence,nausea,itching

6. 1.Treatment of invasive intestinal amoebiasis
•metronidazole or tinidazole are drug of choice.
•Note-it is generally metronidazole combined with diloxanide furoate
and given for 5-7 days.
•Alternatively secnidazole/ornidazole can also be used.
•Drug regimen-metronidazole 400mg tds for 5-7 days followed by
luminal amoebicide[diloxanide furoate]for 5-7 days
•Oral rehydration solution[ors] and zinc tab (in children) should also be
given.
2.Treatment of chronic intestinal amoebiasis/asymptomatic
cyst passers
• Diloxanide furoate 500mg tds *7-10 days is drug of choice
• Nitazoxanide-alternative

7. Treatment of amoebic liver abscess
• Metronidazole/tinidazole is drug of choice
• Dose-met.800mg tds for 7-10days
• Big abscess-aspiration +metronidazole
• Met. sd be followed by luminal amoebocides.
Drugs for giardiasis
• metronidazole[400mg tds * 7days] /tinidazole2gm single
dose or 0.6gbd *7days /secnidazole 2g single dose
• Nitazoxanide 500mg bd for 3 days
• Furazolidone-100mg tds for 5-7 days
Drug for trichomoniasis
• Metronidazole/tinidazole/secnidazole as above-orally
• Natamycin,hamycin,clotrimazole,povidone iodine-intravaginally

8. Drugs for leishmaniasis
• Drugs used for treatment of leishmaniasis[kala-azar]are :
• Antimonial- sodium stibogluconate
• Diamidine- pentamidine
• Antifungal drugs-amphotericin B,ketoconazole,liposomal amphotericicin B
• Others-miltefosine paromomycin allopurinol
Sodium stibogluconate
• MOA-blocks glycolytic and fatty acid oxidation pathways of parasites
• DOSE-20mg/kg/day im[in buttocks]or iv infusionfor 20-30 days.
• High failure rate,extensive resistance-not used nowdays.
• A/E- NVD,meattalic taste,stiffness of injected muscle,liver and kidney
damage
Pentamidine
• Interfers with aerobic glycolysis
• Dose-4mg/kg deep im or slow iv injection[over 1 hour]on alternate days for 5-15
weeks til no parasites are demonstrated in 2 spleenic aspirates take 2 weeks
apart.

9. • A/E- hypotension,dyspnea,palpitation,collapse,vomiting fever,
Local tissue necrosisafter injection,liver and kidney damage,hypoglycemia
• Other use- pneumocystis jiroveci[pneumonia in AIDS patient
Amphotericin B[AMB]
• Drug with highest cure rate in kala-azar.
• Inhibits ergosterol synthesis in leishmanial plasma membrane
• It is indicated in resistant kala-azar and is being commonly used.
• Prolonged hospital stay,grater toxicity,monitoring limits its application
• Dose-0.5-1 mg/kg/day slow iv infusion till 15-20mg /kg is administered
Liposomal amphotericin B
• Now liposomal AMB is commonly used
• Less duration,lesser toxicity,delivers drug inside liver spleen with equivalent
blood level as compared to AMB.
• Dose-3-5 mg/kg/day for 3 days

10. miltefosine
• Only oral antileishmania drug used nowdays
• Dose-100mg/day divided in 2 doses 12 hour apart.