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Long-term anticonvulsant therapy and intestinal calcium absorption
Clinical Pharmacology and Therapeutics
|October 1, 1981
Summary
Anticonvulsant drugs lower fractional calcium absorption (FCaA) in patients. This occurs even when vitamin D levels and the body's response to parathyroid hormone (PTH) are normal.
Area of Science:
- Endocrinology
- Gastroenterology
- Pharmacology
Background:
- Anticonvulsant drugs are widely prescribed.
- Potential side effects include alterations in calcium metabolism.
- The impact on gastrointestinal calcium absorption and PTH response requires clarification.
Purpose of the Study:
- To investigate the effects of anticonvulsant therapy on calcium absorption.
- To assess alterations in the response to parathyroid hormone (PTH).
- To determine changes in serum 25-hydroxy vitamin D (25-OHD) concentrations.
Main Methods:
- Studied twelve patients on anticonvulsant therapy.
- Measured fractional calcium absorption (FCaA) using 45Ca.
- Assessed short-term and calcemic responses to parathyroid extract (PTE) by monitoring urinary cyclic adenosine monophosphate (cAMP) and tubular reabsorption of phosphate (TRP).
Main Results:
- Fractional calcium absorption (FCaA) was significantly lower (30.8% vs. normal 42.2%).
- Serum 25-hydroxy vitamin D (25-OHD) levels were within the normal range.
- Renal response to parathyroid hormone (PTH) was not altered, with expected increases in cAMP and decreases in TRP.
Conclusions:
- Anticonvulsant drugs reduce fractional calcium absorption (FCaA).
- This reduction occurs independently of serum 25-hydroxy vitamin D (25-OHD) levels.
- Gastrointestinal calcium malabsorption is a potential consequence of anticonvulsant therapy, irrespective of PTH response.