This study evaluates the efficacy of melatonin 5mg in the prevention of Delirium in the older adults in emergency department. Half of the participants will receive melatonin 5mg and the other half will use a starch-based placebo.

Melatonia is useful for the treatment of sleep disorders due to the interruption of the circadian rhythm, secondary to alterations caused by the environment. The doses of 5 to 10mg oral or sublingual can improve the quality of the sleep-wake cycle and alertness in short-term use.

Mechanism of action of melatonin are:

1. Binding to membrane receptors: MT1 and MT2 coupled to G protein
2. - Union to nuclear receptors.
3. - Interaction with cytosolic proteins.
4. - Antioxidant of direct and indirect action.
5. - Interaction with mitochondria.

Melatonin circulates 80% bound to albumin and the rest in free form in plasma, 85-90% is metabolized by 6-hydroxymelatonin in the liver, which is then conjugated with sulfuric acid (70-80%) or glucuronic ( 5-3%), and is excreted in urine and feces.

Melatonin and its metabolites act as catalytic antioxidants to safeguard mitochondrial electron transfer reactions, therefore, increases the efficiency of energy metabolism. Melatonin synthesis decreases significantly as age progresses and changes in the circadian cycle have been associated with accelerated aging.

Inclusion Criteria:

• Men and women over 60 who enter the emergency department with a stay in the ward for more than 8 hours and who will remain hospitalized for more than 48 hours due to admission pathology.
• Patients who agree to participate in the study by signing an informed consent (Signature by patient and / or family member).

Exclusion Criteria:

• Patients with a history of dementia or previous neurological diseases.
• Patients with a history of psychiatric disorder.
• Patients diagnosed with any type of liver disease.
• Warfarin treatment.
• Delirium data on admission to the emergency department.
• Patients under invasive mechanical ventilation and sedation.