Amoebiasis is an infection of the intestine, liver, or other tissues caused by a one-celled parasite called Entamoeba histolytica. Amoebiasis is most prevalent in tropical and subtropical countries Poverty, ignorance, overcrowding, poor sanitation and malnutrition favour transmission It is acquired by ingesting food or water contaminated by infected feces.
Mostly they are quite mild and can include loose stools stomach pain abdominal cramps Amoebic dysentery – severe form stomach pain bloody stools fever jaundice anorexia weight loss Rarely the parasite invades liver and forms an abscess and spread to other parts of the body, such as lungs or brain
Medical history, physical examination, lab tests and stool examination Blood test to reveal antibodies against the organism Sigmoidoscopy to evaluate the intestinal wall Radiological studies including ultrasound and CT scans to detect liver abscesses
The choice of drug depends on the severity of the symptom Drugs include Metronidazole Emetine Chloroquine Diloxanide furoate 8 - hydroxyquinoline Tetracycline
Tissue amoebicides For both intestinal and extra intestinal amoebiasis: ▪Nitroimidazoles: Metronidazole, Tinidazole, Secnidazole, Ornidazole, Satranidazole. ▪Alkaloids: Emetine, Dehydroemetine For extraintestinal amoebiasis only: ▪Chloroquine Luminal amoebicides Amide: Diloxanide furoate 8-Hydroxyquinolines: Quiniodochlor, Diiodohydroxyquin Antibiotics: Tetracycline
Prototype nitromidazole.(1959) Highly active amoebicide. Broad spectrum cidal activity against protozoa. It is selectively toxic to anaerobic microorganism. MOA Nitro group is reduced to highly reactive nitro radical that causes damage to DNA and other critical biomolecules by cytotoxicity It disrupts energy metabolism DNA helix destabilization and strand breakage are observed Found to inhibit cell mediated immunity to induce mutagenesis and to cause radiosensitization
Completely absorbed from small intestine Metabolized in liver by oxidation and glucoronide conjucation Excreted in urine Plasma t1/2 is 8hrs ADR Frequent- Anorexia, Nausea, Metallic taste, Abdominal cramps Less frequent-Headache, Glossitis, Dizziness, Rashes Peripheral neuropathy and CNS effects Seizures Thromboflebitis
Equally efficacious as metronidazole Metabolism is slower, t1/2 approx.12hrs Better tolerated Lower incidence of side effects ADRs- Nausea, Rash, Metallic taste Secnidazole Congener of metranidazole Same spectrum of activity and potency Absorption rapid after oral administration Slow metabolism (17-29hrs)
Activity similar to metronidazole Slowly metabolized (12-14hrs) Dose and duration resemble those for Tinidazole Side effect profile is also similar Satranidazole Longer t1/2 (14hrs) Better tolerability No nausea, vomiting or metallic taste, absence of neurological diseases
Neurological diseases Blood dyscrasia First trimester of pregnancy Chronic alcoholism
MOA: Alkaloid from Cephalis ipecacuanha. Potent directly acting amoebicide (trophozoites). Does not kill cysts. Inhibiting protein synthesis in amoebae. Cannot given orally, administered by s.c or i.m injection.
ADR: Cumulative toxicity high It is an irritant; pain, stiffness, eczematous lession at site of injection. Nausea and vomiting, abdominal cramp and diarrhoea, Weakness and stiffness of muscle Hypotension, tachycardia, ECG change, mayocarditis. Contraindicated in presence of cardiac or renal disease and during pregnancy.
USES: Seldom used as Reserve drug in intestinal and extra intestinal amoebiasis Patients not responding / intolerant to metronidazole. Luminal amoebicide follows emetine to eradicate cysts. Also effective in liver fluke infestation. Dihydroemetin = effective but less toxic. Preferred over emetine.
MOA By accumulating in the acidic vesicle of amoeba it raises the vesicular PH interfere with degradation of haemeoglobin by parasitic lyzosomes. PHARMACOKINETICS Oral absorbtion Have the high affinity for melanin and nuclear chromatin Partly metabolised in liver 50% bound in the plasma
Anorexia Epigastric pain Loss of vision due to retinal damage Loss of hearing Mental disturbance Uses Rhematoid arthritis Lepra reaction Photogenic reaction
MOA Luminal amoebicidal Furoate ester hydrolysed in intestine Then released diloxanide which gets largely absorbed Diloxanide is weaker amoebicide than furoate ester. Pharmacokinetics Its is metabolised by glucoronidation. Excreted in urine.
Mild intestinal/asymptomatic amoebiasis Combined with metroniadazole or tinidazole. ADR Occasional nausea Itching Rarely urticaria
Widely employed in past. MOA Active against ENTAMOEBA Kill cyst forming tropozoids in intestine Eradicate cyst from asymptomatic carrier PHARMACOKINETIC Absorption from intestine (10-30%) Absorbed fraction conjugate in liver with glucoronic acid. Excreted in urine. ½ life is 12 hour.
Uses Giardiasis Trichomonas Vaginitis Non specific diarrhoea Dietry indiscretion. Fungal and bacterial skin infection ADR SMON-sub acute myelo optic neuropathy in Japan Goitre Transient loose and green stool
Directly Inhibit amoebae at high concentration. Older tetracycline is incompletely absorbed in the small intestine which reaches colon and inhibits bacterial flora along with Entamoeba living symbiotically. USES: It is adjuvant in chronic, difficult to treat cases Tetracycline lessen risk of opportunistic infection, perforation, peritonitis. When given along with systemic amoebicide. Not good for acute dysentery and for hepatic amoebiasis.
This review compares different drugs used against amoebic colitis, alone or in combination, and also assesses single- dose regimens versus longer regimens. Thirty-seven trials with 4487 participants were included, and only one was of high methodological quality. Tinidazole reduced clinical failure compared with metronidazole and was associated with fewer adverse events. Combination therapy resulted in fewer parasitological failures than metronidazole alone. Tinidazole appears more effective at reducing clinical failures than metronidazole and has fewer associated adverse events. There is insufficient evidence to draw conclusions regarding the efficacy of the other antiamoebic drugs. The choice of antiamoebic drugs would depend largely on the availability and accessibility of drugs. Drugs for treating amoebic colitis
Essential of medical pharmacology by K. D. Tripathi http://www.2.cochrone.org/review/en/ab006 085.html Journal of Ethano pharmacology http://www.medlineplus.com/ http://www.drugs.com/multimedia/pdfs.pdf