David Colquhoun FRS MAE (born 19 July 1936) is a British pharmacologist at University College London (UCL).

Colquhoun runs the website DC's Improbable Science,[3] which is critical of pseudoscience, particularly alternative medicine, and managerialism.

Colquhoun researched the nature of the molecular interactions that cause single ion channels to open and shut, and what it is that controls the speed of synaptic events.

The invention and successful application of the patch clamp technique by Erwin Neher and Bert Sakmann allowed the individual openings and closings of single ion channels to be observed and recorded.

[10] In a lifelong collaboration With the statistician Alan G. Hawkes (1938 -2023),[11] Colquhoun developed a statistical method to interpret the data and test putative quantitative mechanisms for how ion channels function.

[12] He and Lucia Sivilotti run a website,[13]which gives information about UCL's work on single ion channels and on statistical inference.

[16][17] This work led to the first solution of the classical pharmacological problem of measuring separately the affinity and efficacy of an agonist.

This problem remains unsolved for G protein-coupled receptors, because it was shown in 1987 that the classical methods for determining affinity and efficacy were based on a misapprehension.

[23] It was clear that the burst length was what controlled the decay rate of synaptic currents, though the formal relationship was not derived until 1998.

[24] Although the general theory of single channel behaviour was completed in 1982, it could not be used in practice for fitting mechanisms to data, because the recording apparatus is incapable of detecting events shorter than, at best, about 20 microseconds.

[26] The application of the exact solution to joint and conditional distributions in 1996[27] opened the door to maximum likelihood fitting, which was implemented in a computer program, HJCFIT,[28] which has been the basis of subsequent experimental work.

[12] All the early work was based on mechanisms that were essentially generalisations of the simple scheme proposed by del Castillo & Katz in 1957,[29] in which the receptor existed in only two conformations, open and shut.

[35][4] The hazards of reliance on p-values was emphasised in[35] by pointing out that even observation of p = 0.001 was not necessarily strong evidence against the null hypothesis.

[42] In December 2009, Colquhoun won a Freedom of Information judgement, after a three-year campaign, requiring the University of Central Lancashire to release details of their BSc course in homoeopathy.

In addition to his outspoken disapproval of AM in academia, Colquhoun frequently speaks out on his website against misrepresentation of AM as science in the media, and against governmental support of AM.

[48] In response to legal threats from Alan Lakin, husband of Walker, Grant required Colquhoun to remove his website from the UCL server.

Colquhoun was a member of the Conduct and Competence Committee of the Complementary and Natural Healthcare Council (CNHC), a regulatory body for alternative medicine in the UK.

This ludicrous state of affairs arose because nobody in John Major's government had enough scientific knowledge to realise that chiropractic, and some parts of osteopathy, are pure quackery.

The problem is that organisations like the GCC function more to promote their discipline rather than regulate them.Colquhoun was elected a Fellow of the Royal Society (FRS) in 1985[6][2] and awarded the Humboldt Prize in 1990.