- Primary pathogen (Giardia duodenalis (Giardia lamblia, Giardia intestinalis))
- Clinical context (Fecal-oral transmission · untreated water · childcare · travel · malabsorption and failure to thrive in chronic infection)
First-line therapy
Tinidazole • p.o. • 50–50 mg/kg/dose • 1×/day
Max 2000 mg/dose · Max 2000 mg/day · Duration: Single dose · Give with food · FDA-approved in children ≥3 years — use nitazoxanide or metronidazole in younger infants
Enter weight on Kids to calculate doses
Metronidazole • p.o. • 5–5 mg/kg/dose • 3×/day
Max 250 mg/dose · Max 750 mg/day · Duration: 5–7 days · Alternative when tinidazole unavailable or not tolerated — not FDA-approved for giardiasis; suspension may be compounded
- • Metronidazole: alternative when tinidazole unavailable, not tolerated, or in infants <3 years (CDC, AAP, NIH Pediatric OI) — lower cure rates than tinidazole but widely available.
- • Nitazoxanide: preferred in children 1–3 years when tinidazole is not used (FDA ≥1 year); comparable efficacy to metronidazole; also active against Cryptosporidium (CDC, AAP, FDA).
- • Nitazoxanide age ≥12 years: 500 mg BID × 3 days — tablet or 25 mL suspension BID (FDA Alinia label).
- • Persistent or recurrent infection: use alternative agent not used initially; consider longer course or combination therapy; distinguish reinfection from resistance (CDC, StatPearls).
- • Breastfeeding: interrupt breastfeeding during and for 72 hours after tinidazole; metronidazole requires shorter interruption per local guidance (FDA, AAP).
Enter weight on Kids to calculate doses
Clinical notes
- • Treat symptomatic giardiasis with confirmed or highly suspected infection — asymptomatic carriers generally do NOT require treatment in otherwise healthy children (CDC, WHO, AAP).
- • Indications for treatment: acute or chronic diarrhea, abdominal pain, malabsorption, steatorrhea, failure to thrive, weight loss, or immunocompromise (including HIV); confirm with stool antigen, microscopy, or PCR (CDC, AAP Red Book).
- • Persistent or recurrent infection: verify adherence and correct dosing; distinguish reinfection (hygiene/water exposure) from treatment failure; switch to alternate agent (e.g. tinidazole ↔ metronidazole ↔ nitazoxanide) or specialist-guided combination/longer course (CDC, NIH Pediatric OI).
- • Hygiene to prevent reinfection: thorough handwashing, avoid swallowing untreated surface water, safe diaper/childcare practices, launder soiled clothing and bedding (CDC, WHO).
- • Household contacts: routine treatment of asymptomatic contacts is NOT recommended — consider treating asymptomatic contacts only to reduce transmission to immunocompromised persons, pregnant women, or in high-risk settings (childcare, food handling) per public health guidance (CDC, StatPearls).
- • CDC — Giardia infection (Treatment) (2024)
- • AAP Red Book — Giardiasis (2024)
- • NIH / AAP — Pediatric Opportunistic Infections: Giardiasis (2024)
+ 6 more
- • FDA — Tinidazole prescribing information (2024)
- • FDA — Nitazoxanide (Alinia) prescribing information (2024)
- • SEIP / AEPap — Consensus on infectious acute gastroenteritis (2025)
- • ESPGHAN / ESPID — Evidence-based guidelines for management of acute gastroenteritis (2014)
- • NICE NG84 — Diarrhoea and vomiting in under 5s (principles applicable) (2017)
- • WHO — Preventing diarrhoea through better water, sanitation and hygiene (2014)