A further area where evidence for policy is lacking is on the use of metronidazole in severely malnourished children. The WHO guidelines recommend "Metronidazole 7.5 mg/kg every 8 h for 7 days may be given in addition to broad-spectrum antibiotics; however, the efficacy of this treatment has not been established in clinical trials." Metronidazole is effective against Giardia, which is common amongst children with SAM; and against other anaerobic infections, including small bowel bacterial overgrowth and Clostridium difficile colitis. Small cohort studies suggest there may be benefits for nutritional recovery. In Jamaica, half of the children admitted for nutritional rehabilitation had evidence of small bowel anaerobic bacterial overgrowth and this was improved by metronidazole. However, metronidazole can cause nausea and anorexia, potentially impairing recovery from malnutrition and may also cause liver and neurological toxicity. One small study of metronidazole in children with SAM conducted in in Mexico reported significantly prolonged clearance in SAM, without symptomatic toxicity, but suggesting a dosing frequency reduction. Overall, very few pharmacokinetic studies have been done in malnourished children. Changes in body composition as well as metabolic and drug elimination mechanisms may alter the potential toxicity or effective dose.