Busulfan
Severe
Database
Nitroimidazoles inhibit busulfan metabolism, increasing busulfan toxicity (VOD, mucositis).
Avoid combination; if essential, monitor busulfan levels closely.
Source: Kimi deep-research + Cla
Drug reference
Ornidazole
5-nitroimidazole antiprotozoal and antibacterial agent · Antibiotic
Also known as Ornidazole hydrochloride
START
Confirm anaerobic/protozoal indication. Rule out first-trimester pregnancy. Counsel on alcohol abstinence (disulfiram-like reaction).
TYPICAL MAX
Do not exceed 2g/day. Limit duration to ≤10 days unless essential (neuropathy risk).
STOP IF
Signs of peripheral neuropathy (numbness, tingling), seizures, severe rash, jaundice, severe leukopenia.
WATCH
CNS effects (dizziness, ataxia, seizures)—more common with higher doses and longer duration. Alcohol must be avoided during and for 3 days after treatment. Dark urine is expected and harmless.
CDSCO approvedJan AushadhiATC P01AB03
KDIGO 2024 + manufacturer label
- ONSET
- 1h · Onset within 1-2 hours
- PEAK
- 1.5h · Tmax ~1-2 hours
- t½
- 13h · t½ ~12-14 hours
- DURATION
- 12h · 12 hours (BID)
EXCRETION
Renal as metabolites (~65%)
route + CYP
INTERACTIONS
1 major
SEVERE in our sources
PREGNANCY
Avoid in first trimester (no adequate human data; animal studies show teratogenicity at high doses). Second and third trimesters: use only if clearly needed.
FDA category + note
Top interactionssee all 11 →
- BusulfanSevereDatabaseKimi deep-research + Cla
Available in India
59 branded formulations and 61 fixed-dose combinations. Look up specific brands in the Drugs workspace.
Jan Aushadhi — generic available at GoI pharmacies
Mechanism
After intracellular reduction of the nitro group by low-redox-potential electron transport proteins, toxic reduction products interact with microbial DNA, causing strand breakage and loss of helical structure, leading to cell death. Active against anaerobic bacteria and protozoa.
Indications
Amoebiasis (intestinal and hepatic)GiardiasisTrichomoniasisBacterial vaginosisAnaerobic bacterial infections (intra-abdominal, CNS, bone, pelvic)Surgical prophylaxis (anaerobic coverage)H. pylori eradication (combination therapy)
Dosing
- Adult
- Amoebiasis: 500mg PO BID x 5-10 days. Giardiasis: 1.5g PO once daily x 1-2 days. Trichomoniasis: 1.5g PO single dose or 500mg BID x 5 days. Anaerobic infections: 1g IV/PO loading, then 500mg BID. Surgical prophylaxis: 1g IV 30 min pre-op.
- Pediatric
- Amoebiasis/giardiasis: 25-40mg/kg/day divided BID. Max 1.5g/day.
- Renal adjustment
- No adjustment needed (hepatically metabolized).
- Hepatic adjustment
- Reduce dose by 50% in severe hepatic impairment; monitor for toxicity.
- Geriatric
- No specific adjustment; monitor for CNS side effects.
- Max dose
- 1.5g single dose; 2g/day (divided)
Pharmacokinetics
Onset
Rapid; antiprotozoal effect within hours
Peak effect
Tmax 1-2 hours (PO); tissue penetration excellent including CNS
Duration
12 hours (BID dosing)
Half-life
~12-14 hours (allows BID dosing vs metronidazole QID)
Bioavailability
~90%
Protein binding
~15%
Metabolism
Hepatic via oxidation, hydroxylation, and glucuronidation; CYP3A4 and CYP2C9 involved
Excretion
~60-70% renal (metabolites + ~15% unchanged); ~20% fecal
Contraindications
- Hypersensitivity to nitroimidazoles (metronidazole, tinidazole)
- First trimester of pregnancy
- Severe hepatic impairment
- Blood dyscrasias
- CNS disorders (epilepsy, multiple sclerosis—relative)
Side effects
Common
Metallic tasteNausea and vomitingEpigastric discomfortHeadacheDizzinessDry mouthDark urine discoloration (harmless)
Serious
- Peripheral neuropathy (with prolonged use >10 days)
- Seizures
- Leukopenia
- Hepatotoxicity
- Severe cutaneous reactions
- Pancreatitis (rare)
Pregnancy & lactation
Pregnancy
Avoid in first trimester (no adequate human data; animal studies show teratogenicity at high doses). Second and third trimesters: use only if clearly needed.
Lactation
Excreted in breast milk; concentrations similar to plasma. Discontinue breastfeeding during treatment and for 3 days after last dose.
Drug interactions
Alcohol
Moderate
Database
Disulfiram-like reaction (flushing, vomiting, headache, hypotension) due to inhibition of aldehyde dehydrogenase.
Strict alcohol avoidance during treatment and for 3 days after last dose.
Source: Kimi deep-research + Cla
Ciclosporin
Moderate
Database
Increased ciclosporin levels, leading to increased risk of nephrotoxicity and other ciclosporin-related adverse effects.
Monitor ciclosporin trough levels closely. Adjust ciclosporin dose as needed. Monitor renal function.
Cimetidine
Moderate
Database
Increased plasma concentrations of ornidazole, potentially leading to increased risk of ornidazole-related adverse effects (e.g., CNS effects, gastrointestinal disturbances).
Monitor for increased ornidazole adverse effects. Consider dose reduction of ornidazole if necessary.
Fluorouracil
Moderate
Database
Increased risk of fluorouracil-related adverse effects, including myelosuppression, mucositis, and gastrointestinal toxicity.
Monitor for increased fluorouracil toxicity. Consider dose reduction of fluorouracil if co-administration is necessary.
Lithium
Moderate
Database
Increased lithium levels due to reduced renal clearance.
Monitor lithium levels; may need dose reduction.
Source: Kimi deep-research + Cla
Phenobarbital
Moderate
Database
Decreased plasma concentrations of ornidazole, potentially leading to reduced therapeutic efficacy.
Monitor for reduced efficacy of ornidazole. Consider increasing ornidazole dose or using an alternative antibiotic if necessary.
Phenytoin
Moderate
Database
Mutual inhibition of metabolism; levels of both drugs may increase.
Monitor phenytoin levels and for ornidazole CNS toxicity.
Source: Kimi deep-research + Cla
Rifampicin
Moderate
Database
Decreased plasma concentrations of ornidazole, potentially leading to reduced therapeutic efficacy.
Monitor for reduced efficacy of ornidazole. Consider increasing ornidazole dose or using an alternative antibiotic if necessary.
Tacrolimus
Moderate
Database
Increased tacrolimus levels, leading to increased risk of nephrotoxicity and other tacrolimus-related adverse effects.
Monitor tacrolimus trough levels closely. Adjust tacrolimus dose as needed. Monitor renal function.
Warfarin
Moderate
Database
Inhibits warfarin metabolism (CYP2C9), increasing INR and bleeding risk.
Monitor INR closely; reduce warfarin dose by 30-50% during and after therapy.
Source: Kimi deep-research + Cla
Related guidelines
Ask House about Ornidazole
Continue into a citation-backed clinical answer with the drug context already attached.
Sources: KD Tripathi 7e, Harrison 22e·Verified: 2026-05-19 · House clinical team·Cockpit curated: 2026-05-19