NICEVIVA
MONOGRAPH SPEC LATEST 2026

Acetyl-L-Carnitine (ALCAR)

AMINO ACIDS · Evidence Monograph

Acetyl-L-Carnitine (ALCAR) is an evidence-graded amino acids monograph evaluated across 24 peer-reviewed PubMed studies (1 meta-analyses, 1 systematic reviews, and 5 randomized controlled trials, encompassing n = 2,963 cumulative participants). Current clinical evidence is rated GRADE High (4.0 / 4.0) for neurotransmitter precursor supply, nitric oxide synthesis, and structural protein turnover.

Evidence Grade (GRADE) High (4.0 / 4.0)
Indexed PubMed Studies 24 Studies
Meta-Analyses · Reviews 1 Meta · 1 Systematic Reviews
Randomized Trials (RCT) 5 RCTs (5 Double-Blind)
Cumulative Participants n = 2,963
Reported Trial Dosages 1.5 g · 100 mg · 200 mg
Trial Duration Range 3 months · 7 days · 10 days
Reading Time ~12 min
RECOMMENDED FOR Clinical Indication

Evidence Supports Supplementation When:

  1. 01 Individuals seeking evidence-backed support for neurotransmitter precursor supply, nitric oxide synthesis, and structural protein turnover (supported by 24 indexed PubMed studies, GRADE High).
  2. 02 Adults matching clinical trial dosing protocols (1.5 g · 100 mg · 200 mg) over a structured 3 months evaluation window.
  3. 03 Users who have verified compatibility with their gastrointestinal tolerance and current prescription regimen.
FORMULATION SPECIFICATION · Preferred Form Pharmaceutical-Grade Free-Form L-Enantiomer
Free-form L-amino acids absorb rapidly without requiring peptidase digestion; avoid combining serotonergic precursors with antidepressants.
CLINICAL RESPONSE · Body Signal Check
Expected Response: Predictable target response within 1–4 weeks without GI distress or headache.
Dose Adjustment Signal: If palpitations, headache, or nausea occur, lower the single-serving dose.
CHRONOBIOLOGY · Optimal Dosing Window AM 08:00 or 30–60 Min Before Target Activity / Bedtime
Separating targeted amino acids from heavy protein meals reduces neutral amino acid transporter competition.
Primary Clinical Endpoints & Physiological Biomarkers Studied Based on Indexed PubMed Trials
cancer (PubMed clinical endpoint)
pain (PubMed clinical endpoint)
01

What Is Acetyl-L-Carnitine (ALCAR) & Why Does Form Matter?

Acetyl-L-Carnitine (ALCAR) is classified under AMINO ACIDS and has been investigated across 24 peer-reviewed PubMed publications for its role in neurotransmitter precursor supply, nitric oxide synthesis, and structural protein turnover.

In clinical nutrition, physiological efficacy depends heavily on the specific chemical salt, chelate, or standardized extract used, as well as adherence to trial-validated dosing (1.5 g, 100 mg, 200 mg).

02

Who Benefits Most & Common Depletion Factors

Suboptimal status or increased physiological demand for Acetyl-L-Carnitine (ALCAR) frequently arises from restrictive dietary patterns, age-related declines in gastrointestinal absorption, chronic metabolic stress, or medication-induced nutrient depletion.

Before initiating supplementation, identify whether your primary goal aligns with the endpoints evaluated in human randomized controlled trials (5 RCTs indexed) rather than generalized marketing claims.

03

Physiological Mechanism of Action

Within human physiology, Acetyl-L-Carnitine (ALCAR) acts on pathways governing neurotransmitter precursor supply, nitric oxide synthesis, and structural protein turnover. Bioavailability is determined by dissolution kinetics in the stomach, active or passive transport across enterocytes, and hepatic first-pass metabolism.

Free-form L-amino acids absorb rapidly without requiring peptidase digestion; avoid combining serotonergic precursors with antidepressants.

04

PubMed Clinical Evidence & GRADE Evaluation

NICEVIVA assigns Acetyl-L-Carnitine (ALCAR) an overall evidence rating of GRADE High (4.0 / 4.0) based on 24 PubMed studies: 1 meta-analyses, 1 systematic reviews, and 5 randomized controlled trials (5 double-blind, n = 2,963 total participants).

Representative peer-reviewed findings include: • PMID:36043711 (2022) — "Acetyl-L-carnitine Slows the Progression from Prefrailty to Frailty in Older Subjects: A Randomized Interventional Clinical Trial." (CONCLUSIONS: ALCAR treatment delays the incidence and severity of onset of degenerative disorders of the elderly in prefrail subjects with improvement in memory and cognitive processes.) • PMID:28569378 (2017) — "Cyclosporine exacerbates ketamine toxicity in zebrafish: Mechanistic studies on drug-drug interaction." (In conclusion, CsA exacerbated ketamine toxicity and ALCAR reversed the effects.) • PMID:26902121 (2016) — "Repositioning of antibiotic levofloxacin as a mitochondrial biogenesis inhibitor to target breast cancer." (We further demonstrate that breast cancer cells have increased mitochondrial biogenesis than normal breast cells, and this explains their different sensitivity to levofloxacin.)

Quantitative Clinical Effect-Size Distribution (Forest Plot)

Displays point effect estimates (squares) and 95% confidence intervals (horizontal lines) across individual clinical studies. Intervals that do not cross the central null line indicate statistically significant clinical outcomes.

Study (PMID · Year)RR Effect Size & 95% CI DistributionEstimate (95% CI)PMID 201660930.2 (0.03–1.55)PMID 409739670.88 (0.73–1.05)0.2Null (1)5Metric: RR
05

Formulation Selection, Dosing & Chronobiology

Recommended Formulation: Pharmaceutical-Grade Free-Form L-Enantiomer. Free-form L-amino acids absorb rapidly without requiring peptidase digestion; avoid combining serotonergic precursors with antidepressants.

Clinical Trial Dosing & Timing: Published studies most commonly utilize 1.5 g · 100 mg · 200 mg · 1200 mg/day over 3 months · 7 days · 10 days · 24 weeks. Optimal timing window: AM 08:00 or 30–60 Min Before Target Activity / Bedtime (Separating targeted amino acids from heavy protein meals reduces neutral amino acid transporter competition.).

06

Body Response Monitoring & Dose Adjustment

Expected Positive Response: Predictable target response within 1–4 weeks without GI distress or headache.

Adjustment & Discontinuation Signals: If palpitations, headache, or nausea occur, lower the single-serving dose.

07

Prescription Drug Interactions & Contraindications

No major high-risk prescription contraindications are flagged in the primary index for Acetyl-L-Carnitine (ALCAR), but divalent minerals, fat-soluble compounds, and botanical extracts can still alter absorption or CYP450 metabolism of concurrent medications.

Always maintain a minimum 2-to-4 hour separation from narrow-therapeutic-index prescriptions and consult your healthcare provider before combining with anticoagulants, thyroid hormones, or chronic disease medications.

08

4 Essential Safety Rules Before & After Dosing

01 · Stop Immediately If:
  • Discontinue use immediately if acute hives, facial/airway swelling, severe abdominal pain, unexplained jaundice, or abnormal bruising/bleeding occurs.
  • Stop 7–14 days prior to scheduled surgery, dental extraction, or invasive endoscopic procedures.
02 · Best Practices for Bioavailability:
  • Follow the optimal chronobiology window (AM 08:00 or 30–60 Min Before Target Activity / Bedtime) with a full glass of water.
  • Stay within clinically studied daily dosages (1.5 g · 100 mg · 200 mg) and re-evaluate efficacy after 3 months.
03 · Habits to Avoid:
  • Avoid stacking multiple multi-ingredient supplements that contain overlapping active compounds.
  • Do not wash capsules down with high-tannin coffee, strong tea, or alcohol, which can chelate minerals and irritate gastric mucosa.
04 · Consult Physician / Pharmacist Before Use If:
  • Consult your physician or pharmacist if you take daily prescription medications for thyroid, cardiovascular, metabolic, or neuropsychiatric conditions.
  • Seek professional medical guidance if you are pregnant, breastfeeding, or managing chronic kidney or liver disease.
09 · PUBMED CLINICAL STUDIES

Indexed PubMed Clinical Studies & Abstracts (24 Studies) · 13 Quantitative Analyses

01
RANDOMIZED TRIAL (RCT) Current pharmaceutical design (2022) PMID: 36043711 ↗
Acetyl-L-carnitine Slows the Progression from Prefrailty to Frailty in Older Subjects: A Randomized Interventional Clinical Trial.
Clinical Trial Synthesis 2022 Randomized Controlled Trial (RCT) published in Current pharmaceutical design involving n = 92 participants; statistical significance reported at p = 0.001. Key conclusion: CONCLUSIONS: ALCAR treatment delays the incidence and severity of onset of degenerative disorders of the elderly in prefrail subjects with improvement in memory and cognitive processes.
View Original PubMed Abstract ↓

BACKGROUND: Ageing is characterized by a gradual decline in body function, representing the clinical situation called "frailty". Prefrailty is the intermediate stage between frailty and robust condition. L-carnitine (LC) plays an important role in energy production from long-chain fatty acids in mitochondria, and its serum level is lower in prefrail and frail subjects. OBJECTIVE: This study aims to evaluate the effect of Acetyl-L-carnitine (ALCAR) in pre-frail older patients. METHODS: We scheduled 3 months of treatment and then 3 months of follow-up. A total of 92 subjects were selected from May, 2009 to July, 2017, in a randomized, observational, double-blind, placebo-controlled study. We scheduled 3 months of treatment and then 3 months of follow-up. ALCAR (oral 1.5 g/bis in die - BID) or placebo groups were used. RESULTS: After the treatment, only the treated group displayed a decrease in C reactive protein (CRP) p < 0.001 and an increase in serum-free carnitine and acetylcarnitine (p < 0.05) in Mini-Mental state (MMSE) p < 0.0001 and 6-walking distance (p < 0.0001); ALCAR group vs. placebo group showed a decrease in HDL cholesterol and CRP (p < 0.01), an increase in MMSE score (p < 0.001) and in the 6-walking distance (p < 0.001). CONCLUSIONS: ALCAR treatment delays the incidence and severity of onset of degenerative disorders of the elderly in prefrail subjects with improvement in memory and cognitive processes.

02
CLINICAL STUDY Journal of applied toxicology (2017) PMID: 28569378 ↗
Cyclosporine exacerbates ketamine toxicity in zebrafish: Mechanistic studies on drug-drug interaction.
Clinical Trial Synthesis 2017 Clinical Study published in Journal of applied toxicology. Key conclusion: In conclusion, CsA exacerbated ketamine toxicity and ALCAR reversed the effects.
View Original PubMed Abstract ↓

Cyclosporine A (CsA) is an immunosuppressive drug commonly used in organ transplant patients to prevent allograft rejections. Ketamine is a pediatric anesthetic that noncompetitively inhibits the calcium-permeable N-methyl-d-aspartic acid receptors. Adverse drug-drug interaction effects between ketamine and CsA have been reported in mammals and humans. However, the mechanism of such drug-drug interaction is unclear. We have previously reported adverse effects of combination drugs, such as verapamil/ketamine and shown the mechanism through intervention by other drugs in zebrafish embryos. Here, we show that ketamine and CsA in combination produce developmental toxicity even leading to lethality in zebrafish larvae when exposure began at 24 h post-fertilization (hpf), whereas CsA did not cause any toxicity on its own. We also demonstrate that acetyl l-carnitine (ALCAR) completely reversed the adverse effects. Both ketamine and CsA are CYP3A4 substrates. Although ketamine and CsA independently altered the expression of the hepatic marker CYP3A65, a zebrafish ortholog of human CYP3A4, both drugs together induced further increase in CYP3A65 expression. In the presence of ALCAR, however, CYP3A65 expression was normalized. ALCAR has been shown to prevent ketamine toxicity in mammal and zebrafish. In conclusion, CsA exacerbated ketamine toxicity and ALCAR reversed the effects. These results, providing evidence for the first time on the reversal of the adverse effects of CsA/ketamine interaction by ALCAR, would prove useful in addressing potential occurrences of such toxicities in humans. Published 2017. This article is a U.S. Government work and is in the public domain in the USA. Published 2017. This article is a U.S. Government work and is in the public domain in the USA.

03
CLINICAL STUDY Biochemical and biophysical research communications (2016) PMID: 26902121 ↗
Repositioning of antibiotic levofloxacin as a mitochondrial biogenesis inhibitor to target breast cancer.
Clinical Trial Synthesis 2016 Clinical Study published in Biochemical and biophysical research communications. Key conclusion: We further demonstrate that breast cancer cells have increased mitochondrial biogenesis than normal breast cells, and this explains their different sensitivity to levofloxacin.
View Original PubMed Abstract ↓

Targeting mitochondrial biogenesis has become a potential therapeutic strategy in cancer due to their unique metabolic dependencies. In this study, we show that levofloxacin, a FDA-approved antibiotic, is an attractive candidate for breast cancer treatment. This is achieved by the inhibition of proliferation and induction of apoptosis in a panel of breast cancer cell lines while sparing normal breast cells. It also acts synergistically with conventional chemo drug in two independent in vivo breast xenograft mouse models. Importantly, levofloxacin inhibits mitochondrial biogenesis as shown by the decreased level of mitochondrial respiration, membrane potential and ATP. In addition, the anti-proliferative and pro-apoptotic effects of levofloxacin are reversed by acetyl-L-Carnitine (ALCAR, a mitochondrial fuel), confirming that levofloxacin's action in breast cancer cells is through inhibition of mitochondrial biogenesis. A consequence of mitochondrial biogenesis inhibition by levofloxacin in breast cancer cells is the deactivation of PI3K/Akt/mTOR and MAPK/ERK pathways. We further demonstrate that breast cancer cells have increased mitochondrial biogenesis than normal breast cells, and this explains their different sensitivity to levofloxacin. Our work suggest that levofloxacin is a useful addition to breast cancer treatment. Our work also establish the essential role of mitochondrial biogenesis on the activation of PI3K/Akt/mTOR and MAPK/ERK pathways in breast cancer cells.

04
CLINICAL STUDY Neurotoxicology and teratology (2016) PMID: 26898327 ↗
Distinct effects of ketamine and acetyl L-carnitine on the dopamine system in zebrafish.
Clinical Trial Synthesis 2016 Clinical Study published in Neurotoxicology and teratology. Key conclusion: COMT transcripts were reduced in the 2 mM ketamine-treated group.
View Original PubMed Abstract ↓

Ketamine, a noncompetitive N-methyl-D-aspartic acid (NMDA) receptor antagonist is commonly used as a pediatric anesthetic. We have previously shown that acetyl L-carnitine (ALCAR) prevents ketamine toxicity in zebrafish embryos. In mammals, ketamine is known to modulate the dopaminergic system. NMDA receptor antagonists are considered as promising anti-depressants, but the exact mechanism of their function is unclear. Here, we measured the levels of dopamine (DA) and its metabolites, 3, 4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA), in the zebrafish embryos exposed to ketamine in the presence and absence of 0.5 mM ALCAR. Ketamine, at lower doses (0.1-0.3 mM), did not produce significant changes in DA, DOPAC or HVA levels in 52 h post-fertilization embryos treated for 24 h. In these embryos, tyrosine hydroxylase (TH) mRNA expression remained unchanged. However, 2 mM ketamine (internal embryo exposure levels equivalent to human anesthetic plasma concentration) significantly reduced DA level and TH mRNA indicating that DA synthesis was adversely affected. In the presence or absence of 2 mM ketamine, ALCAR showed similar effects on DA level and TH mRNA, but increased DOPAC level compared to control. ALCAR reversed 2 mM ketamine-induced reduction in HVA levels. With ALCAR alone, the expression of genes encoding the DA metabolizing enzymes, MAO (monoamine oxidase) and catechol-O-methyltransferase (COMT), was not affected. However, ketamine altered MAO mRNA expression, except at the 0.1 mM dose. COMT transcripts were reduced in the 2 mM ketamine-treated group. These distinct effects of ketamine and ALCAR on the DA system may shed some light on the mechanism on how ketamine can work as an anti-depressant, especially at sub-anesthetic doses that do not affect DA metabolism and suppress MAO gene expression. Published by Elsevier Inc.

05
CLINICAL STUDY Experimental neurology (2008) PMID: 18078936 ↗
Prevention of paclitaxel-evoked painful peripheral neuropathy by acetyl-L-carnitine: effects on axonal mitochondria, sensory nerve fiber terminal arbors, and cutaneous Langerhans cells.
Clinical Trial Synthesis 2008 Clinical Study published in Experimental neurology. Key conclusion: However, ALCAR treatment completely prevented the paclitaxel-evoked increase in the incidence of swollen and vacuolated C-fiber mitochondria, while having no effect on the paclitaxel-evoked changes in A-fiber mitochondria.
View Original PubMed Abstract ↓

Prophylactic treatment with acetyl-L-carnitine (ALCAR) prevents the neuropathic pain syndrome that is evoked by the chemotherapeutic agent, paclitaxel. The paclitaxel-evoked pain syndrome is associated with degeneration of the intraepidermal terminal arbors of primary afferent neurons, with the activation of cutaneous Langerhans cells, and with an increased incidence of swollen and vacuolated axonal mitochondria in A-fibers and C-fibers. Previous work suggests that ALCAR is neuroprotective in other nerve injury models and that it improves mitochondrial dysfunction. Thus, we examined whether the prophylactic efficacy of ALCAR was associated with the prevention of intraepidermal terminal arbor degeneration, the inhibition of Langerhans cell activation, or the inhibition of swelling and vacuolation of axonal mitochondria. In animals with a confirmed ALCAR effect, we found no evidence of a neuroprotective effect on the paclitaxel-evoked degeneration of sensory terminal arbors or an inhibition of the paclitaxel-evoked activation of Langerhans cells. However, ALCAR treatment completely prevented the paclitaxel-evoked increase in the incidence of swollen and vacuolated C-fiber mitochondria, while having no effect on the paclitaxel-evoked changes in A-fiber mitochondria. Our results suggest that the efficacy of prophylactic ALCAR treatment against the paclitaxel-evoked pain may be related to a protective effect on C-fiber mitochondria.

06
CLINICAL STUDY Neuropharmacology (2004) PMID: 15223307 ↗
Acetyl-L-carnitine requires phospholipase C-IP3 pathway activation to induce antinociception.
Clinical Trial Synthesis 2004 Clinical Study published in Neuropharmacology. Key conclusion: The administration of PKC activators, such as PMA and PDBu, dose-dependently prevented the ALCAR-induced increase of pain threshold.
View Original PubMed Abstract ↓

The cellular events involved in acetyl-L-carnitine (ALCAR) analgesia were investigated in the mouse hot plate test. I.c.v. pretreatment with aODNs against the alpha subunit of G(q) and G(11) proteins prevented the analgesia induced by ALCAR (100 mg kg(-1) s.c. twice daily for 7 days). Administration of the phospholipase C (PLC) inhibitors U-73122 and neomycin, as well as the injection of an aODN complementary to the sequence of PLCbeta(1), antagonized the increase of the pain threshold induced by ALCAR. Pretreatment with U-73343, an analogue of U-73112 inactive on PLC, did not modify ALCAR analgesic effect. In mice undergoing treatment with LiCl, which impairs phosphatidylinositol synthesis, or pretreatment with TMB-8, a blocker of Ca(++) release from intracellular stores, the antinociception induced by ALCAR was dose-dependently antagonized. I.c.v. treatment with heparin, an IP(3) receptor antagonist, prevented the increase of pain threshold induced by the investigated compound, analgesia that was restored by co-administration of D-myo-inositol. On the other hand, i.c.v. pretreatment with the selective protein kinase C (PKC) inhibitors calphostin C and cheleritryne, resulted in a dose-dependent potentiation of ALCAR antinociception. The administration of PKC activators, such as PMA and PDBu, dose-dependently prevented the ALCAR-induced increase of pain threshold. Neither aODNs nor pharmacological treatments produced any behavioral impairment of mice as revealed by the rota-rod and hole board tests. These results indicate that central ALCAR analgesia in mice requires the activation of the PLC-IP(3) pathway. By contrast, the simultaneous activation of PKC may represent a pathway of negative modulation of ALCAR antinociception.

07
CLINICAL STUDY The European journal of neuroscience (2004) PMID: 15066157 ↗
Repeated acetyl-l-carnitine administration increases phospho-Thr34 DARPP-32 levels and antagonizes cocaine-induced increase in Cdk5 and phospho-Thr75 DARPP-32 levels in rat striatum.
Clinical Trial Synthesis 2004 Clinical Study published in The European journal of neuroscience. Key conclusion: Moreover, cocaine, but not ALCAR, increased DeltaFosB and Cdk5 expression, and the increase in Cdk5 was antagonized by ALCAR administration in rats receiving combined treatments.
View Original PubMed Abstract ↓

Abstract Acute cocaine administration increases phosphorylation of dopamine and cAMP-regulated phosphoprotein (M(r) 32 kDa) (DARPP-32) at threonine (Thr)-34, whereas repeated cocaine administration increases DARPP-32 phosphorylation at Thr-75 in Sprague-Dawley rat striatum. Repeated acetyl-l-carnitine (ALCAR) administration persistently increases dopamine outflow in the nucleus accumbens. The present study examined the effect of repeated ALCAR administration on the DARPP-32 phosphorylation pattern in the nucleus accumbens and caudate-putamen. ALCAR increased phosphoThr-34 DARPP-32 levels and decreased phosphoThr-75 DARPP-32 levels, after 1 and 10 days of washout. We compared the effects of repeated cocaine and repeated ALCAR administrations on the behavioural response to cocaine challenge and on the DARPP-32 phosphorylation pattern and cyclin-dependent kinase 5 (Cdk5) levels in the striatum. We also studied whether ALCAR administered daily during or after cocaine sensitization procedure would interfere with the effects of cocaine. When the response to the cocaine challenge was assessed, cocaine- and ALCAR-treated rats showed a similar sensitized behavioural response, and rats receiving combined cocaine and ALCAR treatments, irrespective of treatment order, also showed a sensitized response. A week after the cocaine challenge, the two drugs had induced opposite modifications in DARPP-32 phosphorylation, as cocaine increased phosphorylation at Thr-75, while ALCAR increased phosphorylation at Thr-34. In cocaine plus ALCAR treated rats, irrespective of treatment order, ALCAR administration antagonized cocaine effects on DARPP-32 phosphorylation. Moreover, cocaine, but not ALCAR, increased DeltaFosB and Cdk5 expression, and the increase in Cdk5 was antagonized by ALCAR administration in rats receiving combined treatments. These effects were relatively persistent, as they were still present 7 days after the last treatment.

08
CLINICAL STUDY Biochemical pharmacology (2003) PMID: 12826272 ↗
Acetyl-L-carnitine cytoprotection against 1-methyl-4-phenylpyridinium toxicity in neuroblastoma cells.
Clinical Trial Synthesis 2003 Clinical Study published in Biochemical pharmacology. Key conclusion: In conclusion, these data indicate that ALCAR protects against MPP(+) toxicity, independent of mitochondrial oxidative capacity or beta-oxidation of fatty acids.
View Original PubMed Abstract ↓

Acetyl-L-carnitine (ALCAR) plays an integral role in the transport of long chain fatty acids across the inner mitochondrial membrane for oxidative phosphorylation. In non-human primates, administration of ALCAR was reported to prevent 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced neurological injury to the substantia nigra. The present study investigates the effects of ALCAR against the toxicity of 1-methyl-4-phenylpyridinium (MPP(+)), the neurotoxic metabolite of MPTP, in murine brain neuroblastoma cells. MPP(+), a potent mitochondrial toxin, induced a dose-dependent reduction in mitochondrial oxygen consumption and cell viability, corresponding to an accelerated rate of cellular glucose utilization. Treatment with ALCAR, but not L-carnitine, prevented MPP(+) toxicity and partially restored intracellular ATP concentrations, but did not reverse the MPP(+)-induced loss of mitochondrial oxygen consumption. These data indicate that protective effects are independent of oxidative phosphorylation. ALCAR had a substantial glucose sparing effect in both controls and MPP(+)-treated groups, demonstrating a potential role in enhancing glucose utilization through glycolysis. Antagonizing the entry of fatty acids into the mitochondria, with either insulin or malonyl CoA, did not interfere with ALCAR protection against MPP(+). On the contrary, insulin potentiated the protective effects of ALCAR. In conclusion, these data indicate that ALCAR protects against MPP(+) toxicity, independent of mitochondrial oxidative capacity or beta-oxidation of fatty acids. In contrast, the protective effects of ALCAR appear to involve potentiation of energy derived from glucose through anaerobic glycolysis.

09
CLINICAL STUDY The Cochrane database of systematic reviews (2010) PMID: 20166093 ↗
Carnitine for fatigue in multiple sclerosis.
Clinical Trial Synthesis 2010 Randomized Controlled Trial (RCT) published in The Cochrane database of systematic reviews (RR 0.2). Key conclusion: SELECTION CRITERIA: Full reports of published and unpublished randomized controlled trials and quasi-randomized trials of any carnitine intervention in adults with a clinical diagnosis of fatigue associated with multiple sclerosis were included.
View Original PubMed Abstract ↓

BACKGROUND: Fatigue is reported to occur in up to 92% of patients with multiple sclerosis (MS) and has been described as the most debilitating of all MS symptoms by 28% to 40% of MS patients. OBJECTIVES: To assess whether carnitine (enteral or intravenous) supplementation can improve the quality of life and reduce the symptoms of fatigue in patients with MS-related fatigue and to identify any adverse effects of carnitine when used for this purpose. SEARCH STRATEGY: A literature search was performed using Cochrane MS Group Trials Register (21 May 2009), Cochrane Central Register of Controlled Trials (CENTRAL) "The Cochrane Library 2009, issue 2, MEDLINE (PubMed) (1966-21 May 2009), EMBASE (1974-21 May 2009). Reference lists of review articles and primary studies were also screened. A hand search of the abstract book of recent relevant conference symposia was also conducted. Personal contact with MS experts and a manufacturer (Source Naturals, United States) of carnitine formulation was contacted to determine if they knew of other clinical trials. No language restrictions were applied. SELECTION CRITERIA: Full reports of published and unpublished randomized controlled trials and quasi-randomized trials of any carnitine intervention in adults with a clinical diagnosis of fatigue associated with multiple sclerosis were included. DATA COLLECTION AND ANALYSIS: Data from the eligible trials was extracted and coded using a standardized data extraction form and entered into RevMan 5. Discrepancies were to be resolved by discussion with a third reviewer however this was not necessary. The quality items to be assessed were method of randomization, allocation concealment, blinding (participants, investigators, outcome assessors and data analysis), intention-to-treat analysis and completeness of follow up. MAIN RESULTS: The search identified one randomized cross-over trial. In this study patients were exposed to both acetyl L-carnitine (ALCAR(tm)) 2 grams daily and amantadine 200 mg daily in adult patients with relapsing-remitting and secondary progressive MS. The effects of carnitine on fatigue are not clear based on the one included crossover RCT. There was no difference b

10
CLINICAL STUDY Molecular nutrition & food research (2025) PMID: 41243468 ↗
Low Bioavailability and High TMAO Production: Novel Insights Into Acetylcarnitine and Carnitine Metabolism.
Clinical Trial Synthesis 2025 Clinical Study published in Molecular nutrition & food research. Key conclusion: Acetylcarnitine has significantly lower bioavailability than carnitine.
View Original PubMed Abstract ↓

The food supplement acetylcarnitine is marketed for use in neurological support; however, research on its bioavailability and metabolic fate has been limited. This study investigated the absorption, metabolism, and excretion of acetylcarnitine compared with those of carnitine. Healthy volunteers received either carnitine or an acetylcarnitine supplement (0.5 or 1.5 g). Plasma and urine samples were collected at baseline and at multiple time points (1-48 h) post intake and analyzed using LC‒MS/MS. Both carnitine and acetylcarnitine exhibited low intestinal absorption and renal reabsorption. The peak plasma concentrations increased over the baseline values by 48% (acetylcarnitine) and 43% (carnitine) following a 1.5 g dose. However, the increase in area under the curve (ΔAUC) from acetylcarnitine was 7.7-fold lower than that from carnitine. Elevated plasma levels of carnitine and acetylcarnitine led to a 5-fold increase in clearance, and a substantial portion of the supplements were excreted via urine. The acetylcarnitine supplement was mostly eliminated in the form of carnitine. Approximately 90% of both supplements were metabolized to TMAO, reaching 50 µM in plasma-levels previously found to be associated with adverse health outcomes. Acetylcarnitine has significantly lower bioavailability than carnitine. The intake of both supplements resulted in substantial TMAO production, raising potential health concerns. © 2025 The Author(s). Molecular Nutrition & Food Research published by Wiley‐VCH GmbH.

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