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Telenzepine is a thienobenzodiazepine analogue of pirenzepine with the same M1 preference and far more potency; it reached late stage development as an antiulcer drug in Germany and was overtaken by proton pump inhibitors before launch.
- potent suppression of gastric acid secretion
- a reliable M1-preferring antagonist for tissue and slice pharmacology
- once nightly dosing was sufficient in ulcer trials
- dry mouth, which was dose limiting at 5 mg
- modest slowing of pulse rate
- only about fourfold separation from M3
- no longer available for clinical use, and long term safety never established
Overview
A good demonstration that potency and selectivity are different things. Telenzepine is roughly twenty-five times stronger than pirenzepine against gastric acid in humans and about fifty times stronger against saliva, so the extra potency arrived hardest where nobody wanted it.
- Telenzepine is roughly 25 times more potent than pirenzepine at suppressing gastric acid in humans, but roughly 50 times more potent at suppressing saliva; the potency doubled fastest at the target nobody was aiming for.
Mechanism
Telenzepine is a competitive , not a cholinergic enhancer; swapping the pyridine ring of pirenzepine for a methylthiophene raises affinity roughly tenfold without much changing which subtypes it prefers. In a rat panel it displaced [3H]N-methylscopolamine with Ki values of 1.8 nM at M1, 6.9 nM at M3, 17 nM at M4 and 50 nM at M2, which is about 28 fold preference for M1 over M2 but only about 4 fold over M3.
In functional tissue work it was 4 to 10 times more potent than pirenzepine at suppressing gastric acid secretion and at the smooth muscle and myocardial endpoints alike, and the two drugs showed a similar selectivity profile, so the potency gain was not a selectivity gain [1]. That M1 preference made it a common laboratory for classifying responses: blockade by low nanomolar telenzepine while the M2-preferring antagonists methoctramine and AF-DX 116 stay inactive was a standard argument that a response was M1 mediated [4][5].
receptor fingerprint
M1 (CHRM1)Antagonist
M3 (CHRM3)Antagonist
M4 (CHRM4)Antagonist
M2 (CHRM2)Antagonist
Safetyrisks and cautions, not medical advice
In the human dose ranging study, oral telenzepine inhibited gastric acid dose dependently but suppressed salivary output more steeply still; on a molar basis it was 25 times more potent than pirenzepine against acid and 50 times more potent against saliva, and dry mouth was what limited the 5 mg dose [2]. In the four week duodenal ulcer trial, moderate or severe dry mouth was reported by 14% of patients on 5 mg against 5% on 1.5 mg and 3 mg, and disturbed accommodation was uncommon [3]. Both studies recorded a fall in pulse rate, the expected consequence of muscarinic blockade at cardiac and presynaptic sites [2]. Long term safety was never established, because the compound did not stay in development long enough for anyone to study it.
History
Telenzepine was made at Byk Gulden in Konstanz and first described in 1985 as an antimuscarinic four to ten times more potent than pirenzepine at inhibiting gastric acid secretion. Human work followed quickly: a 1987 dose response study in healthy volunteers put it at 25 times pirenzepine's potency against acid, and a four centre randomised trial in 120 patients with endoscopically confirmed duodenal ulcer settled on 3 mg once nightly as the best of the doses tested, healing 85% of ulcers at four weeks.
It reached preregistration in Germany and went no further; omeprazole and the proton pump inhibitors behind it suppressed acid far more completely and without antimuscarinic effects, and telenzepine is not available for clinical use today. It survives as a research antagonist, and a combination of telenzepine with sertraline was taken into a phase 1 tolerability study in overweight volunteers by Theracos in 2010.
Reputation
Telenzepine is remembered mainly as the more potent pirenzepine. In the muscarinic literature it is a standard M1-preferring antagonist for tissue and slice work; in gastroenterology it is a footnote to the proton pump inhibitor era. Its usefulness as a tool is real but bounded, because its margin over M3 is only about fourfold and the human data show salivary glands are blocked more readily than the stomach is. The fairest reading is as evidence that raw potency at a subtype does not by itself buy a better drug.
Subjective profileweighing the evidence above
A good demonstration that potency and selectivity are different things. Telenzepine is roughly twenty-five times stronger than pirenzepine against gastric acid in humans and about fifty times stronger against saliva, so the extra potency arrived hardest where nobody wanted it.
Resources
This entry is here for reference.
Research
- 1985first citedPharmacological evidence for selective inhibition of gastric acid secretion by telenzepine, a n…
- 1989controlled trial[Dose finding study of telenzepine (1.5 vs. 3 vs 5 mg once daily) in acute treatment of duodena…
- 1990most recentMuscarinic suppression of the evoked N-wave by oxotremorine-M recorded in the guinea-pig olfact…
- 1.Pharmacological evidence for selective inhibition of gastric acid secretion by telenzepine, a new antimuscarinic drug
- 2.Telenzepine is at least 25 times more potent than pirenzepine--a dose response and comparative secretory study in man
- 3.[Dose finding study of telenzepine (1.5 vs. 3 vs 5 mg once daily) in acute treatment of duodenal ulcer. A double-blind, randomized, multicenter parallel group comparison]
- 4.Selective agents for muscarinic receptors linked to phosphoinositide breakdown
- 5.Muscarinic suppression of the evoked N-wave by oxotremorine-M recorded in the guinea-pig olfactory cortex slice
5 listed here; entry last updated August 2026
Reviews
My notesprivate to this device
FAQ
Is telenzepine just a stronger pirenzepine?
Stronger yes, more selective no. The two share nearly the same subtype pattern, and the extra potency turns up at the unwanted receptors as well as the wanted one. In humans the gain against saliva was twice the gain against gastric acid.
Can I get telenzepine?
Not as a medicine. It reached preregistration in Germany, was never launched, and is sold today only as a research chemical for laboratory use.
Does telenzepine act on the brain?
It is routinely used to block M1 responses in brain slice work, so it acts centrally when applied directly to tissue. Whether an oral dose reaches useful brain concentrations in humans has not been established; the clinical trials were designed around a peripheral effect and did not measure anything central.
Adverse effects
- dry mouth, which was dose limiting at 5 mg
- modest slowing of pulse rate
- only about fourfold separation from M3
- no longer available for clinical use, and long term safety never established