Mild hyponatremia is the commonest electrolyte imbalance in the older population. Recently, association between hyponatremia and bone fractures in the ambulatory elderly has been shown.

Mild chronic hyponatremia is causing falls and lead to hospitalisation because of attention deficit.

Symptoms related to hyponatremia can be very subtle and difficult to detect clinically. Twenty elderly patients, retirement homes residents, with serum sodium < 135mEq/L will be included. They will be randomised. The physician will review the drug treatment of ten patients in coordination with the opinion of pharmacologists. Drug treatment for ten other patients wil remained unchanged during the three months of inclusion.

Useful elements of the medical records of patients randomized to the experimental arm will be forwarded to the Pharmacovigilance Regional Center for opinion pharmacologist. The notice, subject to the attention of physician of retirement homes, give rise to a therapeutic approach towards the patient. It will be followed by weekly monitoring of serum sodium for 4 weeks to evaluate the impact of the intervention. Thus, the effectiveness of medical intervention will be evaluated by an objective biological criteria: serum sodium in the fourth week. Secondary endpoints will evaluate the duration of normalization of serum sodium and check the interest of correcting hyponatremia to improve postural capacities and eventually reduce the number of falls in the medium term (three months).

Inclusion Criteria:

• Patient over 65 years Resident of dependent elderly
• Plasma sodium <135 mmol / l less than a week, confirming earlier hyponatremia within a week to three month agreement given after patient information

Exclusion Criteria:

• Venous system does not allow sampling - Patient not taking medication-Dementia