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Salivary and urinary lithium clearance while recumbent and upright
Clinical Pharmacology and Therapeutics
|February 1, 1977
Summary
Lithium clearance in urine decreased when moving from lying down to standing, but saliva lithium clearance remained unchanged. Saliva lithium excretion data may not accurately predict urinary lithium clearance in upright positions.
Area of Science:
- Pharmacokinetics
- Clinical Chemistry
- Renal Physiology
Background:
- Lithium is a medication primarily used to treat bipolar disorder.
- Monitoring lithium levels is crucial due to its narrow therapeutic index.
- Urinary and salivary lithium excretion are potential indicators of systemic lithium levels.
Purpose of the Study:
- To investigate the effect of posture on lithium excretion in urine and saliva.
- To determine the correlation between urinary and salivary lithium clearance in different postures.
- To assess the validity of using salivary lithium levels to estimate urinary lithium clearance.
Main Methods:
- Healthy males received an oral dose of lithium carbonate.
- Urine and saliva samples were collected during recumbent and upright (walking and standing) positions.
- Lithium clearance was measured in both urine and saliva under varying postural conditions.
Main Results:
- Urinary lithium clearance significantly decreased when participants changed from a recumbent to an upright posture.
- Salivary lithium clearance was not significantly affected by the postural change.
- A positive correlation between urinary and salivary lithium clearance was observed only in the recumbent position.
Conclusions:
- Posture significantly influences urinary lithium clearance but not salivary lithium clearance.
- The correlation between urinary and salivary lithium clearance is posture-dependent.
- Extrapolation of salivary lithium excretion data to predict urinary lithium clearance may be unreliable in upright postures.