What medication should be used for treatment?

A 22 year old patient has recently returned from travelling in South Africa, and is unwell with diarrhoea. She had a 2-week history of profuse loose brow n stools, lethargy, weakness, nausea and abdominal discomfort. The diarrhoea had initially settled with loperamide, but then recurred again.
A faecal specimen was collected for microscopy and culture, and it subsequently grew Giardia lamblia.
What medication should be used for treatment?

1.Erythromycin
2.Gentamicin
3.Amoxycillin
4.Albendazole
5.Metronidazole

Summary

Giardia lamblia infection can present with abdominal pains and diarrhoea or steatorrhoea. Metronidazole or tinidazole are first line treatments. It does not cause dysentery (cholera or amoebiasis do). Duodenal aspirate biopsy can confirm the diagnosis. Villous atrophy is associated.