Thiamine Analogues: Benfotiamine vs. Sulbutiamine

Thiamine (vitamin B1) is best known for what happens when it’s missing: confusion, memory problems, and—in severe deficiency—Wernicke encephalopathy and Korsakoff syndrome.

That clinical reality hints at why thiamine biology keeps resurfacing in “brain optimization” conversations. Neurons are unusually dependent on glucose metabolism, and several key enzymes in energy and neurotransmitter pathways require thiamine in its active form (thiamine diphosphate).

The idea behind thiamine analogues is simple: if you can raise functional thiamine availability—especially in nervous tissue—you might improve brain energetics and, in certain contexts, cognition or mental stamina.

Two compounds dominate the modern “nootropic” discussion:

Benfotiamine, a lipid-soluble thiamine prodrug often studied in diabetes-related complications and, more recently, Alzheimer’s disease.
Sulbutiamine, a highly lipophilic thiamine derivative developed to improve brain availability and historically marketed for “asthenia” (a clinical term overlapping fatigue, low drive, and reduced mental energy).

Why thiamine are cognitive agents

A recurring theme in neurodegenerative research is that metabolic changes show up early—sometimes decades before diagnosis.

The rationale for thiamine-based strategies in cognitive decline is that thiamine-dependent enzymes sit at bottlenecks of glucose utilization. If those bottlenecks are impaired, brain networks may become less resilient under the stressors that accumulate with aging and disease.

Benfotiamine and sulbutiamine differ in how they try to solve the “delivery problem”:

Sulbutiamine is described as highly lipophilic and able to cross the blood–brain barrier, and it has been positioned as centrally active in “asthenia” (O. Van Reeth 1999).
Benfotiamine is widely used to raise systemic thiamine-related analytes; in Alzheimer’s-focused trials, investigators explicitly track blood thiamine/esters as proof that dosing meaningfully changes thiamine biology (see below).

Sulbutiamine is often discussed as a central thiamine strategy, while benfotiamine has the strongest clinical cognition data but (mechanistically) may be acting through systemic–metabolic pathways that secondarily affect the brain.

Evidence for Benfotiamine

The most informative controlled study to date is a 12-month, double-blind, placebo-controlled phase IIa trial testing benfotiamine 300 mg twice daily in amyloid-positive amnestic MCI or mild Alzheimer’s (G.E. Gibson et al. 2020).

Participants: 34 benfotiamine vs 36 placebo; mean age ~75.8 years; baseline MMSE ~25.3 (SD 2.6).
Primary outcome (ADAS-Cog): mean 12-month worsening was 3.26 points in placebo vs 1.39 in benfotiamine (ITT analysis), a 43% lower increase numerically, but not statistically significant by simple group comparison (p = 0.162).
Functional/global outcome (CDR): mean 12-month change was 0.22 (placebo) vs 0.05 (benfotiamine), reported as 77% lower worsening with benfotiamine (p = 0.034).
Pharmacokinetics / target engagement: whole-blood thiamine rose from 6.20 ± 2.67 to 999.51 ± 147.4 after 12 months on benfotiamine (described as a 161-fold increase); thiamine diphosphate increased from 64.82 ± 3.00 to 197.39 ± 17.75.
Exploratory biomarkers: serum advanced glycation endproducts (AGEs) showed a significant treatment effect (p = 0.044) and an exploratory FDG-PET “pattern score” analysis reported a treatment effect at one year (p = 0.002).
Safety: the paper reports no adverse events judged related to benfotiamine at this dose over 12 months.

The trial is small, and its primary cognitive endpoint did not reach conventional significance. But it did show a statistically significant difference in a global functional measure (CDR) and strong evidence that the intervention profoundly altered thiamine biology in blood—useful for designing larger trials.

A small 18-month open-label study

An earlier report followed five mild–moderate Alzheimer’s patients taking benfotiamine 300 mg/day for 18 months (X. Pan et al. 2016). MMSE increased by 3.2 points on average at month 18.

Among the three who had follow-up amyloid PET (PiB-PET), amyloid signal (SUVR) increased by 36.7%, while MMSE still rose by ~3 points—suggesting any cognitive change (if real) was not simply explained by reduced amyloid deposition.

This kind of uncontrolled study cannot establish efficacy (practice effects, regression to the mean, and expectancy are major issues), but it helped motivate better-designed trials.

A Larger Trial (BenfoTeam)

A major sign that the field considers benfotiamine biologically interesting is the launch of BenfoTeam, a seamless phase 2A–2B randomized, placebo-controlled trial in 406 participants with early Alzheimer’s over 72 weeks (H.H. Feldman et al. 2024).

In phase 2A, dosing is adaptively chosen between 600 mg and 1200 mg (vs placebo), then carried into phase 2B with co-primary cognitive/functional endpoints including CDR-Sum of Boxes and ADAS-Cog13.

Evidence for Sulbutiamine

Sulbutiamine is often marketed in “nootropic” circles as motivation-enhancing. Clinically, the strongest and most quantifiable findings are in fatigue-adjacent outcomes—where cognitive benefits (if present) tend to be secondary or domain-specific.

Multiple sclerosis fatigue (2-month study)

A commonly cited study assessed MS-related fatigue with sulbutiamine 400 mg daily for two months (S. Sevim et al. 2017). In 26 people with MS, the Fatigue Impact Scale (FIS) total score fell from 77 (SD 30.5) at baseline to 60.5 (SD 29.7) on day 60 (all subscales—including cognitive fatigue—improved; p < 0.01). Notably, benefit clustered in participants on disease-modifying therapy: 13/23 improved vs 0/5 not on DMT.

This supports sulbutiamine as a potential fatigue symptom modifier in a neurologic disease context. It does not demonstrate broad cognitive enhancement in healthy individuals, and it is not a large placebo-controlled cognition trial.

Chronic post-infectious fatigue

A large general-practice trial enrolled 326 patients with chronic post-infectious fatigue and randomized them to sulbutiamine 400 mg/day (n=106), 600 mg/day (n=111), or placebo (n=109) for 28 days (K.P. Tiev et al. 1999).

The overall fatigue evaluation found no significant difference between groups; a short-lived signal appeared at day 7 in women taking 600 mg (p < 0.01), but it did not persist to day 28.

major depressive episodes

In an 8-week randomized, double-blind trial where hospitalized patients with major depressive episodes received clomipramine, sulbutiamine 600 mg/day did not outperform placebo on core depression rating scales at 4 weeks.

Baseline severity was substantial (MADRS 32, HAM-A 23, CGI 5, psychomotor scale ERD 27). However, disability and subjective inhibition measures (including affective/cognitive facets) improved significantly in the sulbutiamine group (H. Lôo et al. 2000).

Alzheimer’s adjunct evidence

A randomized, double-blind trial examined sulbutiamine combined with a cholinesterase inhibitor (donepezil) in mild–moderate Alzheimer’s, reporting domain-specific improvements (attention in both groups early; episodic memory and daily activities improving in the combination sequence) (H. Ollat et al. 2007).

Neurological effects beyond cognition

Benfotiamine’s neurological literature is heavily shaped by diabetic neuropathy research:

In BENDIP, 165 patients with diabetic polyneuropathy were randomized to 600 mg/day, 300 mg/day, or placebo. After 6 weeks, the Neuropathy Symptom Score differed significantly in the per-protocol analysis (p = 0.033) and was borderline in ITT (p = 0.055); Total Symptom Score showed no significant difference. (H. Stracke et al. 2008).
A 12-month randomized, placebo-controlled, double-blind trial in type 2 diabetes with symptomatic neuropathy (BOND study) reported 57 randomized participants. The primary morphometric endpoint (corneal nerve fiber length) and a wide range of secondary neuropathy outcomes did not differ; only Neuropathy Symptom Score “tended” to improve (p = 0.098). Benfotiamine significantly increased all measured thiamine analytes (p ≤ 0.003 vs placebo) and was well tolerated (D. Ziegler et al. 2026).

This pattern—strong biochemical engagement but weak or inconsistent clinical signal—is a theme you also see in cognition trials and is exactly why larger, better-powered studies are now underway.

Vascular/AGE biomarker trials

Because glycation and vascular dysfunction intersect with brain health, benfotiamine has been tested on intermediate biomarkers.

In a 12-week randomized trial in type 2 diabetes with nephropathy-range albumin excretion, 39 received benfotiamine and 43 placebo; benfotiamine did not significantly reduce plasma or urinary AGEs or markers of endothelial dysfunction/inflammation (A. Alkhalaf et al. 2012).

That doesn’t rule out brain effects, but it argues against assuming benfotiamine reliably “fixes” glycation biology in all clinical contexts.

Sulbutiamine safety

In the MS fatigue study, there were no serious adverse events over two months.
However, sulbutiamine has a small cluster of psychiatric case reports suggesting possible triggering of mania/hypomania in vulnerable individuals (case-report literature; not proof of causality).

A neutral take is that sulbutiamine’s “activation” profile—one reason it’s sought as a nootropic—may also be the reason clinicians should be cautious in people with bipolar-spectrum risk.

Thiamine analogues as nootropics

There are not many modern, well-powered trials showing meaningful gains in learning, working memory, or executive function in healthy adults.

Benfotiamine has the clearest controlled signal suggesting slower functional/global decline in early Alzheimer’s over 12 months (CDR change 0.22 → 0.05, p = 0.034) with large effects on thiamine analytes (e.g., blood thiamine ~6 → ~1000).
Sulbutiamine has its best quantitative support for fatigue reduction, including the cognitive fatigue domain in MS (FIS 77 → 60.5, p < 0.01), with mixed results in other fatigue syndromes.

Thiamine analogues are like context-dependent metabolic modulators—with the best near-term cognitive relevance in early Alzheimer’s research for benfotiamine, and in fatigue/drive-related symptoms for sulbutiamine.

The key question isn’t whether thiamine biology matters for the brain—it does—but whether boosting it can produce clinically meaningful cognitive benefits.

The near-term answer will likely hinge on:

BenfoTeam’s large 72-week trial (406 participants, 600 vs 1200 mg adaptive selection) and whether it replicates or strengthens the earlier CDR/ADAS signals.
Better clarity on who responds (e.g., genotype/biomarker subgroups suggested in earlier work).
For sulbutiamine, whether future trials use placebo-controlled designs with cognition-first endpoints rather than fatigue-only outcomes.

References

Alkhalaf A, Klooster A, van Oeveren W, Achenbach U, Kleefstra N, et al. (2012). Effect of Benfotiamine on Advanced Glycation Endproducts and Markers of Endothelial Dysfunction and Inflammation in Diabetic Nephropathy. PLoS ONE. “https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0040427”

Feldman HH, et al. (2024). Protocol for a seamless phase 2A-phase 2B randomized, double-blind, placebo-controlled 72-week clinical trial of benfotiamine in early Alzheimer’s disease. PLoS ONE. “https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0302998”

Gibson GE, et al. (2020). Benfotiamine and Cognitive Decline in Alzheimer’s Disease: Results of a Randomized Placebo-Controlled Phase IIa Clinical Trial. Journal of Alzheimer’s Disease. “https://pubmed.ncbi.nlm.nih.gov/33074237/”

Lôo H, et al. (2000). Effects of sulbutiamine (Arcalion 200) on psycho-behavioral inhibition in major depressive episodes. Encephale. “https://pubmed.ncbi.nlm.nih.gov/10858919/”

Ollat H, Laurent B, Bakchine S, et al. (2007). Effects of the association of sulbutiamine with an acetylcholinesterase inhibitor in early stage and moderate Alzheimer disease. Psychogeriatrics. “https://pubmed.ncbi.nlm.nih.gov/17675917/”

Pan X, et al. (2016). Long-Term Cognitive Improvement After Benfotiamine Administration in Patients with Alzheimer’s Disease. Neuroscience Bulletin. “https://pubmed.ncbi.nlm.nih.gov/27696179/”

Sevim S, et al. (2017). Sulbutiamine shows promising results in reducing fatigue in patients with multiple sclerosis. Multiple Sclerosis and Related Disorders. “https://pubmed.ncbi.nlm.nih.gov/28755683/”

Stracke H, Gaus W, Achenbach U, Federlin K, Bretzel RG. (2008). Benfotiamine in diabetic polyneuropathy (BENDIP): results of a randomised, double blind, placebo-controlled clinical study. Experimental and Clinical Endocrinology & Diabetes. “https://pubmed.ncbi.nlm.nih.gov/18473286/”

Tiev KP, et al. (1999). [Treatment of chronic postinfectious fatigue: randomized double-blind study of two doses of sulbutiamine (400–600 mg/day) versus placebo]. Revue de Médecine Interne. “https://pubmed.ncbi.nlm.nih.gov/10573727/”

Van Reeth O. (1999). Pharmacologic and therapeutic features of sulbutiamine. Drugs Today (Barc). “https://pubmed.ncbi.nlm.nih.gov/12973384/”

Ziegler D, et al. (2026). Effects of benfotiamine treatment over 12 months on morphometric, neurophysiological and clinical measures in type 2 diabetes with distal symmetric polyneuropathy (trial report). (Journal page via PubMed / PMC). “https://pubmed.ncbi.nlm.nih.gov/41571333/”

(Case-report summary) Reactions Weekly (2013; issue dated 2011). Sulbutiamine: Mania—case report. “https://link.springer.com/article/10.2165/00128415-201113790-00126”