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# D-Citrulline (as L-Citrulline)
## Overview
D-Citrulline is the dextrorotatory enantiomer of citrulline, an amino acid. L-citrulline, the naturally occurring enantiomer, is more commonly used therapeutically and is the focus of most clinical data. L-citrulline is a precursor to L-arginine, which is involved in nitric oxide production.
## Primary Indications
* Primary Pulmonary Hypertension (PPH)
* Sickle Cell Disease (SCD) - to improve endothelial function and reduce vaso-occlusive events.
* Erectile Dysfunction - due to its role in nitric oxide synthesis.
* Exercise Performance Enhancement - potential to reduce fatigue and improve endurance.
## Adult Dosing
* **Pulmonary Hypertension:** Typically initiated at 3 grams TID, titrating up to 6 grams TID.
* **Sickle Cell Disease:** 3 grams BID.
* **Erectile Dysfunction:** 3-6 grams once daily.
* **Exercise Performance:** 2-5 grams once daily, taken 60-90 minutes before exercise.
Maximum dose generally not well-established and depends on indication.
## Pediatric Dosing
* **Sickle Cell Disease:** 150 mg/kg/day divided BID, not to exceed 3 grams BID.
* **Pulmonary Hypertension:** Dosing is not well-established in pediatric populations.
## Dose Adjustments
No specific dose adjustments are typically required for hepatic or renal impairment, as L-citrulline is metabolized and excreted without significant hepatic involvement. However, caution is advised in severe renal dysfunction.
## Contraindications
* Hypersensitivity to L-citrulline or any component of the formulation.
* Concurrent use with nitrates (e.g., nitroglycerin, isosorbide mononitrate/dinitrate) due to potential for additive hypotensive effects.
## Adverse Effects
Generally well-tolerated.
* Gastrointestinal: Nausea, diarrhea, abdominal discomfort.
* Cardiovascular: Hypotension (especially when combined with antihypertensives or nitrates).
* Other: Headache, dizziness.
## Key Drug Interactions
* **Nitrates (e.g., nitroglycerin, isosorbide dinitrate/mononitrate):** Additive hypotensive effects. Avoid concurrent use.
* **Antihypertensives (e.g., ACE inhibitors, ARBs, diuretics, beta-blockers):** Potential for additive blood pressure lowering effects. Monitor blood pressure closely.
* **Phosphodiesterase-5 (PDE5) inhibitors (e.g., sildenafil, tadalafil):** Potential for additive hypotensive effects. Use with caution.
## Monitoring
* Blood pressure: Monitor for hypotension, especially when initiating therapy or with concomitant antihypertensive medications.
* Renal function: In patients with pre-existing renal disease.
* Symptoms of pulmonary hypertension or sickle cell disease progression.
## Clinical Pearls
* L-citrulline is often preferred over L-arginine supplements due to better oral bioavailability and direct increase in plasma L-arginine levels.
* For sickle cell disease, L-citrulline is thought to improve endothelial function by increasing nitric oxide production, potentially reducing pain crises.
* The efficacy and optimal dosing for exercise performance are still under investigation.
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*This information is intended for healthcare professionals. Always consult the most current prescribing information and relevant clinical guidelines before making therapeutic decisions. Dosing can vary based on individual patient factors and specific product formulations.*
