13. Serum potassium, magnesium, and calcium levels should be at least within institutional normal limits, and every effort should be made to keep potassium concentrations above 4.0 mEq/dL, magnesium concentrations above 1.8 mg/dL, and serum calcium at normal concentration with the administration of oral/IV potassium and/or magnesium and/or calcium replacement during the study. If this is not possible, potassium and magnesium (and calcium) concentrations should at least be kept within institutional normal limits.