Established constipation can be treated with various drugs (eg, bisacodyl 5 to 15 mg orally every 24 hours, milk of magnesia 15 to 30 mL orally at bedtime, lactulose 15 to 30 mL (10 to 20 g) every 12 to 24 hours, magnesium citrate 195 to 300 mL once every 24 hours.