Summary

The interaction between lithium and naproxen is clinically significant, as naproxen can increase lithium blood levels and potentially lead to lithium toxicity. This interaction requires careful monitoring and possible dose adjustments when both medications are used concurrently.

Introduction

Lithium is a mood stabilizer primarily used to treat bipolar disorder and prevent manic episodes. It belongs to the class of antimanic agents and has a narrow therapeutic window. Naproxen is a nonsteroidal anti-inflammatory drug (NSAID) commonly used to treat pain, inflammation, and fever. It works by inhibiting cyclooxygenase enzymes and is available both over-the-counter and by prescription for various inflammatory conditions.

Mechanism of Interaction

Naproxen reduces lithium clearance by the kidneys through inhibition of prostaglandin synthesis. NSAIDs like naproxen decrease renal blood flow and glomerular filtration rate by blocking prostaglandin E2 and prostacyclin production. Since lithium is primarily eliminated unchanged through the kidneys, this reduction in renal function leads to decreased lithium excretion and subsequent accumulation in the blood, potentially reaching toxic levels.

Risks and Symptoms

The primary risk of this interaction is lithium toxicity, which can manifest as nausea, vomiting, diarrhea, tremor, confusion, drowsiness, and in severe cases, seizures, coma, or kidney damage. Lithium levels can increase by 15-60% when combined with NSAIDs. Patients with pre-existing kidney disease, dehydration, or those taking other medications affecting kidney function are at higher risk. The interaction typically develops within days to weeks of starting naproxen therapy.

Management and Precautions

Close monitoring of lithium serum levels is essential when naproxen is initiated, discontinued, or dose-adjusted. Lithium levels should be checked within 4-7 days of starting naproxen and regularly thereafter. Consider reducing lithium dose by 25-50% when starting naproxen, with subsequent adjustments based on serum levels and clinical response. Alternative pain management options such as acetaminophen should be considered when possible. If naproxen is necessary, use the lowest effective dose for the shortest duration, ensure adequate hydration, and monitor kidney function regularly.

Lithium interactions with food and lifestyle

Lithium has several important food and lifestyle interactions that require careful monitoring. Sodium intake significantly affects lithium levels - both low sodium diets and sudden increases in sodium intake can alter lithium concentrations and potentially lead to toxicity or reduced effectiveness. Patients should maintain consistent sodium intake and avoid drastic dietary changes. Adequate fluid intake (8-10 glasses of water daily) is essential, as dehydration can increase lithium levels and risk of toxicity. Caffeine intake should be kept consistent, as sudden changes in caffeine consumption can affect lithium levels. Alcohol should be avoided or used with extreme caution, as it can increase the risk of lithium toxicity and may worsen mood symptoms. Patients should also avoid excessive sweating through intense exercise or saunas without proper hydration, as fluid loss can concentrate lithium levels. These interactions are well-documented in major drug databases and clinical guidelines, requiring regular monitoring of lithium blood levels.

Naproxen interactions with food and lifestyle

Alcohol: Concurrent use of naproxen with alcohol increases the risk of gastrointestinal bleeding and ulceration. Patients should avoid or limit alcohol consumption while taking naproxen. Food: Taking naproxen with food or milk can help reduce gastrointestinal irritation and stomach upset. While not required for efficacy, administration with food is recommended to minimize GI side effects.