RESEARCH MONOGRAPH · KDC-MN-048

Tacrine

May 9, 2026 Kodiac biolabs Research Revised May 30, 2026 2 min read

Our opinion on this compound

63/100

The first AChE inhibitor approved for Alzheimer's, now mostly historical, but the pharmacology is still useful

Tacrine is the molecule that essentially launched the modern AChE-inhibitor field. Summers' group ran the first systematic Alzheimer trials with it in the 80s, the FDA approved it in 1993 as Cognex, and it stayed in clinical use for about a decade before donepezil and the second-generation inhibitors made it obsolete. The hepatotoxicity is what killed it. Roughly 30% of patients developed clinically significant ALT elevations, and that was the end of tacrine as a usable drug.

What's actually interesting about it from a research-tool perspective is the receptor profile, which is messier and more multi-target than its successors. Tacrine inhibits both AChE and BuChE, but it also has affinity at NMDA receptors (channel block, similar pattern to memantine but weaker), monoamine oxidase, and at higher concentrations, several voltage-gated potassium channels. So as a probe it's dirty, but the dirty profile is exactly what makes it occasionally useful for medicinal chemistry SAR work.

The aminoacridine scaffold also generated a whole family of analogs that informed how the field thought about cholinesterase pharmacology. The hybrid molecules (tacrine-melatonin, tacrine-ferulic acid, tacrine-trolox) that came out of the 2000s were attempts to keep the cholinesterase activity while addressing the liver toxicity and adding antioxidant function. None of them advanced clinically but the SAR is informative.

What we like: historical importance, multi-target profile that's pedagogically useful for understanding why selectivity matters, and the molecule is cheap and widely available for research purposes.

What we dont like: the hepatotoxicity is real, the off-target profile is broad enough that interpretation in any model gets complicated, and the molecule isnt the right answer for most modern cholinesterase research questions. Better tools exist.

Sourcing is straightforward. The molecule has been a research reagent for decades, multiple suppliers carry it, HPLC validation is standard, and the hydrochloride salt is stable and easy to work with.

For research, tacrine is occasionally useful as a positive control or as a starting point for SAR work in the aminoacridine series. Most of the time donepezil or galantamine is the cleaner choice.

Evidence: 75
Mechanism: 70
Reliability: 75
Safety: 40
Sourcing: 85
Value: 65
Signal: 50
Staying power: 45

Plain-language summary Intrigue 48 / 100

Tacrine, sold as Cognex, was the first FDA-approved Alzheimer disease medication (1993). It is rarely prescribed today owing to hepatotoxicity, but remains a research reference compound for cholinesterase inhibition. Not stocked by Kodiac. This monograph is provided for research and educational reference.

Intrigue 0–100 blends mechanism novelty, evidence strength, and translational potential. Kodiac editorial, not peer-reviewed.

Aminoacridine acetylcholinesterase inhibitor

The first FDA-approved Alzheimer disease therapy (1993), withdrawn for hepatotoxicity but historically important and retained as a research probe.

Abstract

Tacrine (Cognex, 1,2,3,4-tetrahydroacridin-9-amine; CAS 321-64-2; molecular formula C13H14N2; molecular weight 198.27) is the first FDA-approved cholinesterase inhibitor for Alzheimer disease, granted approval in 1993 and subsequently withdrawn from the US market in 2013 due to hepatotoxicity (approximately 50 percent of patients developed clinically significant ALT elevation requiring monitoring or discontinuation). The compound is a non-selective reversible AChE and BChE inhibitor based on an aminoacridine scaffold. Mechanism includes additional weak NMDA receptor antagonism and modest sodium channel blockade, distinguishing the pharmacology from the more selective subsequent AChE inhibitors. The historical significance of tacrine is substantial; the compound established cholinesterase inhibition as a viable therapeutic strategy for Alzheimer disease and led to development of the more tolerable second-generation agents. The compound retains research utility as a pharmacological probe and AChE reference compound. Pharmacokinetics: short half-life (3 to 4 hours). Hepatotoxicity is dose-related and reversible on discontinuation in most cases.

Mechanism of action

Non-selective AChE and BChE inhibitor; secondary NMDA antagonism and sodium channel blockade.

Reported research dose ranges

Reported research dose ranges in the literature span 40 to 160 mg (when marketed).

References

Davis KL, et al. A double-blind, placebo-controlled multicenter study of tacrine for Alzheimer's disease. N Engl J Med 1992.
Watkins PB, et al. Hepatotoxic effects of tacrine administration in patients with Alzheimer's disease. JAMA 1994.

Read the full monograph

The full reference document covers compound identification, discovery and developmental history, mechanism of action, pharmacokinetics, reported research dose ranges, sourcing and quality verification, reconstitution and handling, stack interaction considerations, and a curated reference list. Available as a research-use-only PDF download.

KDC-MN-049

The full reference document is provided strictly for research use only. It reports research dose ranges from the published literature, not instructions for use in humans or animals.

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FOR RESEARCH USE ONLY. Not for medical, diagnostic, or therapeutic purposes. Not for human consumption. All information is provided for research and educational purposes only.

Kodiac sells research compounds for investigative use only.

Tacrine

Abstract

Mechanism of action

Reported research dose ranges

References

Read the full monograph

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Abstract

Mechanism of action

Reported research dose ranges

References

Read the full monograph

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