Alanyl-Glutamine: Evidence, Mechanism, Dosing & Status

Alanyl-glutamine (Ala-Gln, N(2)-L-alanyl-L-glutamine; brand Dipeptiven, Fresenius Kabi) is a small synthetic dipeptide engineered as a stable, highly water-soluble delivery vehicle for glutamine — a conditionally essential amino acid that is too unstable and poorly soluble to put into standard IV solutions.20 Unlike the gray-market research peptides that dominate this encyclopedia, it is a legitimate pharmaceutical with a deep human evidence base. This monograph separates what is genuinely proven from what is contested.

This article is informational and editorial content for research and educational purposes only. It is not medical advice, not a protocol to follow, and not a sourcing or buying guide. Alanyl-glutamine in its principal evidenced form (Dipeptiven) is a clinician-administered parenteral product for hospitalized patients. Dosing figures are reported strictly as seen in the published literature for completeness — not as recommendations. Consult a licensed clinician before any health decision.

What is alanyl-glutamine and how does it work?

Chemically, alanyl-glutamine is a dipeptide formed by an amide bond between L-alanine and L-glutamine (molecular formula C₈H₁₅N₃O₄), a white crystalline, non-animal-derived solid.21 Its design solves a pharmaceutical problem: free L-glutamine is unstable in aqueous solution — it degrades to ammonia and pyroglutamate, cannot be heat-sterilized, and has limited solubility — so it is omitted from standard commercial parenteral-nutrition solutions. Conjugating glutamine to alanine yields a compound with high solubility, high thermal stability, and a long shelf life, finally allowing glutamine to be delivered intravenously.20

The core mechanism is therefore not receptor signaling but stable delivery — alanyl-glutamine behaves like a prodrug. After IV infusion it is rapidly hydrolyzed by ubiquitous plasma and tissue dipeptidases in the extracellular space, liberating free L-glutamine and L-alanine in equimolar amounts. Pharmacokinetics are striking: the terminal half-life is only about 2.4 to 3.8 minutes, with renal elimination of the intact dipeptide under 5 percent.20 The released glutamine then functions normally — as the primary respiratory fuel for rapidly dividing cells (enterocytes, lymphocytes, macrophages), a nitrogen donor for nucleotide and glutathione synthesis, and a substrate that becomes conditionally essential when demand outstrips supply in critical illness, trauma, sepsis, surgery, and burns.1

Given orally, the intact dipeptide takes a different route: it is absorbed by intestinal epithelium and enhances coupled sodium-water absorption, outperforming free glutamine or glucose alone. Proposed reasons include greater stability than free glutamine at low gut pH, augmentation of ion transport through mucosal signaling, and glutamine's role as the enterocyte's preferred fuel — supporting mucosal repair and tight-junction integrity.1318

What is the evidence by indication?

Alanyl-glutamine is one of the rare compounds in this field with abundant human randomized controlled trials. The table below grades the major indications; note that the headline parenteral-nutrition use carries an essential, contradictory counter-signal that follows it.

The strongest evidence is for parenteral nutrition. A 2017 systematic review and meta-analysis (Stehle et al.) restricted to 15 RCTs and 842 critically ill adults dosed per guideline — parenteral Ala-Gln 0.3 to 0.5 g/kg/day, no hepatic or renal failure, hemodynamically stable, with adequate nutrition — found significant benefit: infectious complications RR 0.70 (95% CI 0.60–0.83), hospital mortality RR 0.55, ICU length of stay reduced by 1.61 days, and hospital stay reduced by 2.30 days.1 Landmark single trials support this: the French double-blind multicenter RCT (Déchelotte et al., n=114) showed Ala-Gln-TPN at 0.5 g/kg/day reduced infectious complications and improved glucose tolerance,2 the Spanish multicenter RCT (Grau et al., n=127) assessed nosocomial infection and 6-month mortality,3 and earlier work showed reduced morbidity in severe acute pancreatitis and improved 6-month outcomes.45

How can the same compound help and harm? The reconciliation is a dose-and-selection story. The harm tracked supraphysiologic combined enteral-plus-parenteral dosing, administration to patients in shock or renal failure, and inadequate co-fed calories — exactly the conditions excluded from Stehle's guideline-concordant pooled analysis. Notably, a meta-analysis of enteral glutamine alone did not show increased mortality, localizing the risk to high-dose parenteral overload in unstable patients.11 Post-2013, major ASPEN and ESPEN guidelines no longer recommend high-dose IV glutamine in the unstable, multi-organ-failure ICU patient, while parenteral glutamine dipeptide may still be considered for stable patients on exclusive PN. The functional-medicine reading is blunt: repletion to normal in a stable patient is not the same intervention as pharmacologic overload in collapsing physiology.

Beyond the ICU, oral alanyl-glutamine has Grade A–B human evidence for restoring intestinal-barrier function. A randomized double-blind placebo-controlled trial improved intestinal permeability and reduced diarrhea in HIV patients while improving antiretroviral drug levels,15 and the IMAGINE program studied oral Ala-Gln for gut integrity and weight velocity in undernourished children.16 A published RCT protocol (the ACT trial) is testing it as an adjunct for Clostridioides difficile infection.17 Smaller crossover RCTs of oral Ala-Gln (Sustamine) suggest acute hydration and performance benefit under dehydration in athletes, though these are small, single-lab studies without large multi-site replication.1314 You can review one of the registry-listed gut studies directly at ClinicalTrials.gov (NCT01832636).

What doses appear in the literature?

Reported strictly as information, not a protocol. For parenteral use, the approved-abroad product Dipeptiven 20% is given at a maximum of about 0.5 g/kg/day of Ala-Gln, always as a supplement to amino-acid solutions and never as the sole nitrogen source, with at least 1.0 g/kg/day of other amino acids (total amino acid ≥1.5 g/kg/day) and not exceeding roughly 30 percent of total nitrogen; it is admixed into the carrier bag, never given undiluted as a bolus.202 The high-dose ICU regimen used in REDOXS — about 0.35 g/kg/day IV glutamine as Ala-Gln plus ~30 g/day enteral — is associated with harm and is not a recommended regimen.7 Oral gut-barrier studies in undernourished children used up to 24 g/day for about 10 days,16 while athletic-hydration studies used roughly 0.05 to 0.2 g/kg per bolus, or 1 to 2 g per 500 mL of fluid, divided across rehydration timepoints.1314

How safe is alanyl-glutamine?

At guideline parenteral doses in stable patients, alanyl-glutamine is well tolerated; pooled RCT data show benefit, not net harm, on infection and length of stay, and because it is hydrolyzed to physiologic amino acids cleared like any infused amino acid, systemic accumulation is minimal.120 Reported adverse events are mostly infusion-related — chills, rigors, transient temperature or sweating — alongside the general cautions of amino-acid infusions. A liver-safety study found IV Ala-Gln did not significantly raise blood ammonia or cause brain edema in a moderate-liver-dysfunction model.22

The dominant safety finding, however, is the excess mortality with high-dose glutamine in unstable ICU patients seen in REDOXS and MetaPlus, hypothesized to stem from impaired clearance in renal-failure subgroups, supraphysiologic combined dosing, and inadequate co-fed energy.10 Accordingly, alanyl-glutamine is contraindicated or used with great caution in severe renal failure (CrCl under about 25 mL/min), severe hepatic insufficiency, multi-organ failure or shock at the time of dosing, and inborn errors of amino-acid metabolism; pregnancy and lactation data are inadequate.20 A theoretical tumor-fuel concern exists because glutamine fuels rapidly dividing cells, though this is not established as clinical harm in the supplementation trials.

What is the FDA and WADA status in 2026?

In the United States, alanyl-glutamine does not have FDA marketing approval as a parenteral-nutrition drug; it has been used investigationally under an Investigational New Drug application in clinical trials and is explicitly described in trial consent documents as not approved by the FDA and considered investigational.23 (Note that free L-glutamine has a separate, approved oral product, Endari, for sickle-cell disease — a different product.) Internationally the picture is the opposite: it is approved and marketed as Dipeptiven (Fresenius Kabi) across the EU, UK, China, and much of Asia and Latin America as a PN additive, ATC code B05XB02.20 In oral form, L-alanyl-L-glutamine (for example Sustamine) is sold as a dietary-supplement ingredient. It is not a DEA controlled substance.

For athletes the status is favorable: neither glutamine nor alanyl-glutamine appears on the WADA Prohibited List, in or out of competition, including the 2026 update.2425 The standing caveat is supplement contamination — surveys have found banned substances in a meaningful share of products — so WADA-tested athletes should verify specific products through GlobalDRO and choose third-party-tested brands rather than trusting labels.24

Bottom line. Alanyl-glutamine is a legitimate, evidence-graded clinical-nutrition tool, not a speculative peptide — and a textbook lesson that more is not better. As a guideline-dose PN additive in stable surgical and ICU patients it reduces infections and shortens stays (Grade A); orally it restores gut-barrier integrity (Grade A–B); and it shows promising but small athletic-hydration data (Grade B). The benefit is strictly conditional on dose and patient selection: high-dose glutamine in multi-organ failure increased mortality in two large RCTs. It is not FDA-approved in the US, widely approved abroad as Dipeptiven, and not prohibited in sport. Regulatory facts here are current as of mid-2026; confirm FDA and WADA listings directly before acting, as status can change.