L-CITRULLINE

L-Citrulline is also produced from arginine as a by-product of the reaction catalyzed by NOS family. 
L-Citrullines name is derived from citrullus, the Latin word for watermelon, from which it was first isolated.
L-Citrulline has a role as an EC 1.14.13.39 (nitric oxide synthase) inhibitor, a protective agent, a nutraceutical, a micronutrient, a human metabolite, an Escherichia coli metabolite, a Saccharomyces cerevisiae metabolite and a mouse metabolite. 

CAS Number: 372-75-8
Molecular Formula: C6H13N3O3
Molecular Weight: 175.19
EINECS Number: 206-759-6

Synonyms: L-citrulline, citrulline, 372-75-8, delta-Ureidonorvaline, Sitrulline, N5-Carbamoyl-L-ornithine, (S)-2-Amino-5-ureidopentanoic acid, L-Cytrulline, Citrulline, L-, N(delta)-Carbamylornithine, N5-(Aminocarbonyl)ornithine, N5-carbamoylornithine, alpha-Amino-delta-ureidovaleric acid, N5-(Aminocarbonyl)-L-ornithine, L-2-Amino-5-ureidovaleric acid, L-Ornithine, N5-(aminocarbonyl)-, (2S)-2-amino-5-(carbamoylamino)pentanoic acid, 2-Amino-5-ureidovaleric acid, 29VT07BGDA, 2-Amino-5-uredovaleric acid, CHEBI:16349, Ngamma-carbamylornithine, N(5)-(aminocarbonyl)-L-ornithine, NSC-27425, DTXSID80883373, DTXCID301022909, 206-759-6, (2S)-2-azaniumyl-5-(carbamoylamino)pentanoate, alpha-Amino-gamma-ureidovaleric acid, CHEBI:18211, NSC27425, H-cit-oh, L(+)-citrulline, MFCD00064397, Ornithine, N5-(aminocarbonyl)-, L-citrullin, cit, d-ureidonorvaline, (2S)-2-amino-5-(aminocarbonylamino)pentanoic acid, CIR, L-(+)-Citrulline, C6H13N3O3, (2S)-2-Amino-5-(carbamoylamino)pentanoic Acid (Citrulline), Ornithine, N5-carbamoyl-, L- (8CI), N5-carbamylornithine, N5-carbamoyl-L-ornithine, EINECS 206-759-6, NSC 27425, UNII-29VT07BGDA, Cytrulline, Ureidonorvaline, Ureidovalerate, H-Orn(carbamoyl)-OH;L-Citrulline, L-Citruline, Ornithine, N5-carbamoyl-, L-, gammaureidonorvaline, N-carbamylornithine, L-Citrulline, 4, Amino-ureidovalerate, ND-carbamylornithine, N()-carbamylornithine, L-Citrulline (DCF), L-Citrulline, 98%, Ndelta-Carbamylornithine, starbld0002494, Amino-ureidovaleric acid, Ndelta-carbamy-ornithine, CITRULLINE [MI], A-amino-d-ureidovalerate, L-Citrulline (Standard), 2-Amino-5-uredovalerate, 2-Amino-5-ureidovalerate, L-N5-carbamoyl-Ornithine, CITRULLINE [VANDF], bmse000032, bmse000800, bmse000858, CITRULLINE [MART.], CITRULLINE [WHO-DD], A-amino-d-ureidovaleric acid, L-2-Amino-5-ureidovalerate, N(5)-carbamoyl-L-ornithine, SCHEMBL20588, GTPL722, N5-(aminocarbonyl)-Ornithine, L-2-Amino-5-ureido-valerate, L-CITRULLINE [USP-RS], CHEMBL444814, orb1302545, Alpha-amino-delta-ureidovalerate, Alpha-amino-gamma-ureidovalerate, BDBM92903, HY-N0391R, (S)-2-Amino-5-ureidopentanoate, L(+)-2-Amino-5-ureidovalerate, MSK8335, L-2-Amino-5-ureido-valeric acid, L-Citrulline, >=98% (TLC), HY-N0391, pentanoic acid, 2-amino-5-ureido-, L(+)-2-Amino-5-ureidovaleric acid, s3798, SBB012374, AKOS005259571, AKOS006240677, CCG-266398, CS-W019940, DB00155, FC15792, SMP1_000146, NCGC00142602-01, AC-23976, AS-12594, BP-14067, ST069317, SY023288, (2S)-2-amino-5-(carbamoylamino)pentanoate, (S)-2-amino-5-(aminocarbonyl)aminopentanoate, N(SUP 5)-(AMINOCARBONYL)-L-ORNITHINE, C00327, D07706, D71216, EN300-251063, M03230, (S)-2-amino-5-(aminocarbonyl)aminopentanoic acid, Q408641, L-2-AMINO-5-(CARBAMOYLAMINO)PENTANOIC ACID, EA65B21D-61C4-4748-9E9F-0CF6EDF9A21D, Z1198149761, (S)-2-Amino-5-ureidopentanoic acid,;L-2-Amino-5-ureidovaleric acid, L-Citrulline, United States Pharmacopeia (USP) Reference Standard, Ibuprofen Impurity 78;Arginine Impurity 2（Arginine EP Impurity B）（Citrulline）;L-CTRULLINE;L-Citrullne;Arginine EP Impurity B;n5-(aminocarbonyl)-l-ornithin;N5-(aminocarbonyl)-L-Ornithine;ALPHA-AMINO-DELTA-UREIDO-N-VALERIC ACID

L-Citrulline is the L-enantiomer of citrulline. 
L-Citrulline is an enantiomer of a D-citrulline. 
L-Citrulline is a tautomer of a L-citrulline zwitterion.

L-Citrulline is an amino acid. 
L-Citrulline is made from ornithine and carbamoyl phosphate in one of the central reactions in the urea cycle. 
Inhalation of L‑citrulline refers to the potential delivery of this amino acid directly to the lungs, a method that is still being explored in experimental and preclinical studies. 

L-Citrulline is best known as a natural precursor to L‑arginine, which in turn serves as a substrate for nitric oxide (NO) production, an essential molecule involved in the relaxation of blood vessels, regulation of airway tone, and reduction of inflammation in lung tissues. 
Delivering L‑citrulline directly to the respiratory system could provide targeted benefits, particularly in conditions where NO availability is impaired.
Inhaled L‑citrulline is being investigated as a way to enhance nitric oxide production locally in lung tissues, which can lead to improved vasodilation and better blood flow within the pulmonary circulation. 

This approach has shown promise in experimental models for conditions such as pulmonary hypertension, bronchopulmonary dysplasia, and oxygen-induced lung injury, where restoring NO levels helps protect and repair lung structures. 
The direct delivery bypasses systemic circulation and targets the lungs, potentially allowing for smaller doses with fewer side effects.
Although most studies have focused on oral or intravenous forms, their results provide insight into what inhalation might achieve. 

Systemically administered L‑citrulline increases L‑arginine levels more efficiently than taking L‑arginine itself, leading to enhanced NO synthesis. 
This mechanism supports airway relaxation, improved lung function, and better oxygen exchange. 
In conditions like asthma, increased NO availability has been linked to better symptom control, reduced airway inflammation, and improved breathing performance.

L-Citrulline is an amino acid found in watermelon. 
L-Citrulline is also made in the body. 
The body changes L-citrulline into another amino acid called L-arginine.

The name citrulline comes from Citrullus vulgaris, the Latin term for watermelon. Unlike some amino acids, L-citrulline isn't used to make protein, but it might help increase other chemicals the body needs to make protein. 
L-Citrulline might also help improve blood flow and reduce blood pressure.

L-Citrulline is converted to L-arginine by argininosuccinate synthase. 
L-arginine is in turn responsible for citrulline's therapeutic affects. 
Many of L-arginine's activities, including its possible anti-atherogenic actions, may be accounted for by its role as the precursor to nitric oxide or NO. 

NO is produced by all tissues of the body and plays very important roles in the cardiovascular system, immune system and nervous system. NO is formed from L-arginine via the enzyme nitric oxide synthase or synthetase (NOS), and the effects of NO are mainly mediated by 3',5' -cyclic guanylate or cyclic GMP. 
NO activates the enzyme guanylate cyclase, which catalyzes the synthesis of cyclic GMP from guanosine triphosphate or GTP. 

L-Citrulline is converted to guanylic acid via the enzyme cyclic GMP phosphodiesterase. 
L-Citrulline is a heme-containing enzyme with some sequences similar to cytochrome P-450 reductase. 
Several isoforms of NOS exist, two of which are constitutive and one of which is inducible by immunological stimuli. 

The constitutive NOS found in the vascular endothelium is designated eNOS and that present in the brain, spinal cord and peripheral nervous system is designated nNOS. 
The form of NOS induced by immunological or inflammatory stimuli is known as iNOS. 
iNOS may be expressed constitutively in select tissues such as lung epithelium. 

All the nitric oxide synthases use NADPH (reduced nicotinamide adenine dinucleotide phosphate) and oxygen (O2) as cosubstrates, as well as the cofactors FAD (flavin adenine dinucleotide), FMN (flavin mononucleotide), tetrahydrobiopterin and heme. 
Interestingly, ascorbic acid appears to enhance NOS activity by increasing intracellular tetrahydrobiopterin. 
L-Citrulline and nNOS synthesize NO in response to an increased concentration of calcium ions or in some cases in response to calcium-independent stimuli, such as shear stress. 

In vitro studies of NOS indicate that the Km of the enzyme for L-arginine is in the micromolar range. 
The concentration of L-arginine in endothelial cells, as well as in other cells, and in plasma is in the millimolar range. 
In other words, L-arginine would not be expected to be rate-limiting for the enzyme, and it would not appear that supraphysiological levels of L-arginine which could occur with oral supplementation of the amino acid would make any difference with regard to NO production. 

The reaction would appear to have reached its maximum level. However, in vivo studies have demonstrated that, under certain conditions, e.g. hypercholesterolemia, L-arginine could enhance endothelial-dependent vasodilation and NO production.
L-Citrulline is a nonessential amino acid that is made in the body, consumed in foods, and is available as a dietary supplement. 

L-Citrulline helps the body eliminate harmful substances such as ammonia, may have antioxidant effects, acts as a vasodilator (widening the blood vessels), and may have other purported benefits that include improved athletic performance.
L-Citrulline is an amino acid derived from ornithine in the catabolism of proline or glutamine and glutamate, or from l-arginine via arginine-citrulline pathway.

Melting point: 214 °C
alpha: 25.5 º (c=8, 6N HCl)
Boiling point: 306.48 °C (rough estimate)
Density: 1.2919 (rough estimate)
Refractive index: 26 ° (C=8, 6 mol/L HCl)
Storage temp.: Keep in dark place, sealed in dry, room temperature
Solubility: Aqueous acid (sparingly), water (slightly)
Form: Crystals or crystalline powder
pKa: 2.43 (at 25 °C)
Color: White
Odor: Odorless
Optical activity: +4.025 (H₂O), +24.225 (1 mol dm⁻³ HCl)
Water solubility: 200 g/L (20 °C)
Merck: 14,2331
BRN: 6055157
InChIKey: RHGKLRLOHDJJDR-BYPYZUCNSA-N
LogP: -3.190

Inhalation of L‑citrulline is an emerging concept that combines the known benefits of this amino acid with a delivery method that directly targets lung tissues. 
By boosting local nitric oxide production, it has the potential to improve lung function, reduce pulmonary artery pressure, and protect delicate respiratory structures from damage. 
While current research is still in early stages, the results from systemic use suggest that inhaled L‑citrulline could become a valuable therapeutic approach for a variety of respiratory conditions in the future.

The concept of inhaling L‑citrulline fits into a broader movement toward targeted respiratory therapies that aim to deliver active compounds directly to the lungs. 
As research progresses, it may become part of combination treatments, perhaps alongside bronchodilators, anti-inflammatory agents, or oxygen therapy, to enhance therapeutic outcomes in complex respiratory diseases. 
Furthermore, inhaled formulations could be adapted to different patient groups, from infants with developmental lung problems to adults with chronic conditions.

The inhalation of L‑citrulline represents a promising direction in pulmonary medicine, combining the well-established benefits of L‑citrulline with the efficiency of targeted lung delivery. 
By directly increasing nitric oxide levels in the respiratory system, this approach has the potential to improve breathing capacity, reduce pulmonary vascular resistance, and protect lung tissues against inflammation and oxidative injury. 
Although this therapeutic method is still under development, its strong biological basis and wide range of potential applications make it an exciting candidate for future respiratory treatments.

While L‑citrulline is generally considered safe when consumed orally, inhalation requires additional safety evaluations. 
Factors such as particle size, formulation stability, and potential irritation to airways must be thoroughly assessed. 
Clinical trials would be needed to confirm its safety profile, determine optimal dosing, and identify any long-term effects of repeated inhalation.

Citrulline is obtained as a result of a reaction of L-arginine hydrochloride with sodium hydroxide, copper oxide and hydrogen sulfide.
L-citrulline is used for Alzheimer's disease, dementia, fatigue, muscle weakness, sickle cell disease, erectile dysfunction, high blood pressure, and diabetes. 
L-Citrulline is used for heart disease, body building, increasing energy, and for improving athletic performance.

L-Citrulline, when orally administered is found to ameliorate the condition of sickle cell disease in humans. 
L-citrulline can be a replacement for L-arginine administration in case of defective NO synthetase. 
L-Citrulline supplementation is found to fulfill the purpose of NO-dependent signaling.

However, the supplement may affect the way certain drugs work in your body. 
Do not take this supplement if you are taking: A non-essential amino acid and a precursor of arginine. 
Citrulline supplements have been claimed to promote energy levels, stimulate the immune system and help detoxify ammonia (a cell toxin). 

L-Citrulline is made from L-ornithine and carbamoyl phosphate in one of the central reactions in the urea cycle. 
L-Citrulline is also produced from L-arginine as a by-product of the reaction catalyzed by the enzyme NO synthase. 
L-citrulline, while being an amino acid, is not involved in protein synthesis and is not one of the amino acids coded for by DNA. 

Although citrulline cannot be incorporated in proteins during protein synthesis, several proteins are known to contain citrulline as an amino acid. 
These citrulline residues are generated by a family of enzymes called peptidylarginine deiminases (PADs), which convert the amino acid arginine into citrulline. 
Proteins that contain citrulline residues include myelin basic protein (MBP), fillagrin and several histone proteins.

Beyond lung-specific effects, L‑citrulline is known to enhance circulation, reduce blood pressure, and improve oxygen utilization in muscles. 
These systemic effects indirectly support respiratory efficiency during exercise or under stress. 
Inhaled forms, if developed successfully, could amplify these benefits by directly addressing the respiratory system’s needs.

Inhalation of L‑citrulline can be considered an innovative therapeutic approach that aims to harness the biological properties of this amino acid directly within the respiratory system. 
Unlike oral supplementation, where the compound must undergo digestion and metabolism before reaching the bloodstream, inhalation has the potential to deliver L‑citrulline directly to the pulmonary tissues, allowing for faster action and localized effects.
When inhaled, L‑citrulline would directly reach the epithelial cells of the lungs, where it is quickly converted into L‑arginine by specific cellular enzymes. 

This increased L‑arginine pool fuels nitric oxide (NO) synthesis within the lung environment. 
NO acts as a powerful signaling molecule, promoting the relaxation of bronchial and vascular smooth muscle, thereby improving airway patency and enhancing blood flow through the pulmonary capillaries. 
This dual effect—airway dilation and vascular dilation—has a significant impact on improving oxygen transfer efficiency in the lungs.

Additionally, NO produced locally in response to inhaled L‑citrulline exerts anti-inflammatory effects by reducing the activity of pro-inflammatory cells and cytokines. 
L-Citrulline also has antioxidant properties, limiting the damage caused by oxidative stress, which is a common factor in many chronic lung diseases. 
This protective role makes inhaled L‑citrulline potentially valuable in conditions where oxidative injury and inflammation damage lung structures.

Inhaled L‑citrulline may lower elevated blood pressure in the pulmonary arteries by increasing NO availability, improving right heart function, and reducing strain on the heart and lungs.
By increasing NO levels, inhaled L‑citrulline may help reduce airway constriction and improve airflow. 
This could also enhance the response to bronchodilators, offering an additional tool in asthma management.

L-Citrulline involves persistent inflammation and airway narrowing. 
Inhalation therapy with L‑citrulline could contribute to reducing inflammation, easing breathing difficulties, and possibly slowing disease progression.

In premature infants who often suffer from underdeveloped lungs and oxygen-related injuries, inhaled L‑citrulline could help stimulate normal vascular growth and alveolar development, protecting against conditions like bronchopulmonary dysplasia.
By enhancing NO production, inhaled L‑citrulline may improve oxygen delivery and reduce airway reactivity during intense physical activity, benefiting athletes or individuals with exercise-induced bronchoconstriction.

Uses Of L-Citrulline:
L-Citrulline, is used as an essential intermediate in the biosynthesis of nitric oxide from L-arginine. 
L-Citrulline is also used as a nutritional drink and biochemical reagent.

An amino acid, L-Citrulline can be used in the treatment of asthenia and as an essential intermediate in the biosynthesis of nitric oxide.
L-Citrulline has a wide range of uses due to its unique biological role as a non‑essential amino acid involved in the urea cycle and as a precursor for L‑arginine, which in turn boosts nitric oxide (NO) production. 
These properties give it applications in medical treatments, sports nutrition, metabolic health, and experimental therapies involving respiratory function.

L‑citrulline is widely used to support cardiovascular health because it naturally increases nitric oxide levels, leading to relaxation of blood vessels, improved circulation, and lower blood pressure. This makes it beneficial in conditions such as hypertension, endothelial dysfunction, and pulmonary arterial hypertension. 
L-Citrulline is also used in medical settings to support patients with heart failure, where better vascular function enhances oxygen delivery and reduces strain on the heart. 
Its ability to enhance nitric oxide synthesis also makes it a candidate for improving respiratory conditions, as increased NO helps dilate pulmonary vessels and airways, improving lung function and oxygen exchange.

L‑citrulline is an integral component of the urea cycle, the pathway by which the body removes excess nitrogen produced during protein metabolism. 
Supplementation with L‑citrulline is therefore used to manage certain urea cycle disorders, rare genetic conditions where patients cannot efficiently eliminate ammonia from the body. 
By enhancing the removal of nitrogen as urea, citrulline supplementation helps prevent toxic ammonia buildup, protecting the brain and other organs from damage.

Because of its role in boosting nitric oxide and improving circulation, L‑citrulline is popular in sports nutrition. 
Athletes use it to improve endurance, delay fatigue, and enhance recovery after intense exercise. 
The increased blood flow delivers oxygen and nutrients more effectively to muscles during training, reducing soreness and promoting faster healing. 

In addition, it helps clear ammonia, a byproduct of intense exercise, which contributes to muscle fatigue. 
This dual action—better oxygenation and reduced metabolic waste—explains its widespread use in pre‑workout supplements.
L‑citrulline is sometimes used as a natural aid for erectile dysfunction (ED). 

Its ability to increase nitric oxide enhances blood flow not only to the heart and muscles but also to the penile tissues, supporting the physiological mechanisms required for an erection.
While it is not as potent as pharmaceutical drugs for ED, it may provide a safer, well‑tolerated alternative for men seeking a natural option.
Supplementation with L‑citrulline has shown benefits in improving immune function, as it is involved in amino acid metabolism that supports immune cell activity. 

L-Citrulline may also help regulate metabolism in conditions such as diabetes, where vascular health and insulin sensitivity are often impaired. 
Additionally, by reducing oxidative stress and inflammation through nitric oxide pathways, it contributes to overall immune resilience.
Although primarily studied in oral form, L‑citrulline has potential uses in the treatment of respiratory diseases. 

By increasing nitric oxide in the lungs, it may help dilate airways, improve pulmonary blood flow, and reduce inflammation. 
This has led to investigations into its role in managing asthma, pulmonary hypertension, chronic obstructive pulmonary disease (COPD), and even lung injury in premature infants. 
In these conditions, supplementation may improve breathing efficiency, oxygenation, and lung tissue health.

In neonatal care, L‑citrulline is being explored as a therapeutic agent for bronchopulmonary dysplasia (BPD), a condition affecting premature babies whose lungs are underdeveloped. 
By stimulating nitric oxide production, it supports normal vascular and alveolar development, reducing the risk of long‑term breathing difficulties. 
Early intervention with citrulline could enhance lung function in infants who have been exposed to prolonged oxygen therapy.

Researchers are currently investigating L‑citrulline in other fields, including neuroprotection, metabolic syndrome management, and chronic inflammatory conditions. 
Its antioxidant and anti‑inflammatory properties make it a candidate for slowing the progression of degenerative diseases or reducing tissue damage in high‑stress physiological states. 
Future applications may also include aerosolized or inhaled formulations, which could directly target lung tissue for improved local effects in respiratory diseases.

Beyond clinical and therapeutic settings, L‑citrulline is widely used as a dietary supplement to improve general wellness, support vascular health, and boost energy levels. 
L-Citrulline is commonly found in formulations aimed at heart health, workout enhancement, and recovery support. 
Because it is naturally present in foods such as watermelon, supplementation is considered safe and well‑tolerated for most individuals.

The uses of L‑citrulline are diverse, ranging from medical treatments for cardiovascular, metabolic, and respiratory disorders to performance enhancement in athletics and overall health support. 
Its unique role as a nitric oxide booster and urea cycle component allows it to positively influence circulation, detoxification, and tissue repair. 
Emerging research continues to expand its potential applications, particularly in the field of targeted respiratory therapies, where localized delivery could maximize benefits for lung health.

L‑Citrulline is not just an amino acid supplement; it is a compound with multifaceted applications in medicine, wellness, and biotechnology, owing to its central role in metabolic pathways and its ability to enhance nitric oxide production. 
Its uses can be further elaborated to show how it contributes to various areas of health and research.
Although most studies focus on its cardiovascular and muscular effects, L‑citrulline may also benefit brain health. 

By improving blood flow to the brain through nitric oxide–mediated vasodilation, it can enhance oxygen and nutrient delivery to neural tissues. 
This may support cognitive performance, memory, and overall mental clarity, particularly in aging individuals where vascular-related cognitive decline is common. 
Additionally, nitric oxide plays a role in neurotransmission, suggesting that citrulline could indirectly support brain signaling processes.

Another emerging use of L‑citrulline is in accelerating wound healing. 
Nitric oxide, produced as a result of citrulline metabolism, is known to facilitate collagen deposition, angiogenesis (the growth of new blood vessels), and cellular repair. 
These processes are crucial for the healing of skin injuries, burns, and even internal tissue damage. 

In this way, citrulline supplementation can potentially be applied in clinical settings to improve recovery after surgeries or trauma.
While it is already popular in athletic circles for reducing muscle soreness, its benefits extend beyond muscle recovery. 
By improving systemic circulation, L‑citrulline enhances the removal of metabolic waste products such as lactic acid and ammonia, which accumulate during strenuous physical activity. 

This not only aids in faster recovery but also allows athletes to train more intensely with shorter rest periods. 
Its role in reducing exercise-induced oxidative stress further contributes to protecting muscle fibers from damage.
L‑citrulline helps in managing chronic fatigue by improving mitochondrial efficiency and oxygen utilization at the cellular level. 

In individuals with conditions that cause persistent tiredness—such as chronic fatigue syndrome or fibromyalgia—this amino acid may help restore energy balance and reduce feelings of exhaustion. 
Furthermore, by supporting blood flow and nutrient delivery, it optimizes the energy metabolism required for day-to-day activities.
The compound has potential uses in managing metabolic disorders, including insulin resistance and type 2 diabetes. 

Its ability to improve vascular function and reduce oxidative stress can help counteract the complications associated with these conditions. 
Additionally, citrulline supplementation may influence hormonal balance by supporting pathways related to growth hormone secretion during exercise, which further enhances recovery and muscle development.
Since L‑citrulline is naturally produced in the kidneys from ornithine and carbamoyl phosphate, supplementation may support kidney function in conditions where renal nitric oxide production is impaired. 

L-Citrulline can help maintain renal blood flow and filtration efficiency, which are critical for detoxification and electrolyte balance. 
For patients with mild kidney dysfunction, citrulline supplementation may offer a supportive role in maintaining renal health.
L‑citrulline is often combined with other therapeutic agents to amplify their effects. 

For example, it may be paired with antioxidants to further reduce oxidative stress, or with L‑arginine to synergistically boost nitric oxide production. 
In sports nutrition, it is commonly combined with branched-chain amino acids (BCAAs) or creatine to maximize performance and recovery. 
This versatility allows it to be integrated into numerous treatment and supplementation strategies.

Safety Profile Of L-Citrulline:
L‑Citrulline is generally considered a safe amino acid, especially when used as a dietary supplement or in clinical treatments under controlled conditions. 
However, when discussing its hazards—particularly in the context of inhalation, high doses, or industrial handling—certain risks must be considered. 
These hazards include possible effects on health, environmental risks, and concerns related to improper usage.

While L‑citrulline is not classified as a toxic inhalant, the inhalation of its powdered form during manufacturing or handling can cause mechanical irritation of the respiratory tract. 
Dust particles may irritate the nose, throat, and lungs, leading to symptoms such as coughing, sneezing, and mild discomfort. 
In sensitive individuals, this irritation may provoke shortness of breath or exacerbate pre-existing respiratory conditions like asthma. 

Prolonged exposure to airborne dust in poorly ventilated areas can increase the risk of respiratory stress.
Direct contact with L‑citrulline powder can occasionally cause mild irritation to the skin and eye discomfort, especially if particles enter the eyes. 
Symptoms may include redness, itching, or a gritty sensation. 

While these effects are typically temporary and non-severe, protective equipment such as gloves and safety goggles is recommended in industrial settings.
Although L‑citrulline is safe in recommended doses, excessive intake can lead to gastrointestinal disturbances such as stomach pain, nausea, diarrhea, or bloating. 
Extremely high doses might also influence blood pressure due to its vasodilatory effects, potentially causing dizziness, headaches, or hypotension (abnormally low blood pressure), particularly in individuals already taking medications for hypertension.

Because L‑citrulline enhances nitric oxide production, it has the effect of dilating blood vessels. 
While this is beneficial in many therapeutic contexts, it can become hazardous in individuals who already have low blood pressure, or those taking medications that lower blood pressure. 
Combining citrulline with such medications could result in excessive hypotension, leading to fainting or cardiovascular instability.