International Association Against Painful Experiments on Animals

101 Misleading results from Vivisection Animal Experiments

14: Blood Pressure Pill Leads to Withdrawal Syndrome

During the 1960s animal experiments suggested that clonidine might be a useful drug for preventing migraine.(1) Using cats, experimenters found that clonidine interfered with physiological processes thought to cause headaches. The drug was introduced in 1969 but clinical experience now suggests that clonidine is largely ineffective and little better than a dummy pill.(1)

Clonidine proved more successful in the treatment of high blood pressure. Its ability to lower blood pressure was discovered accidentally when it was given to people as a nasal decongestant.(2) Although effective, there were serious unexpected side-effects when patients stopped taking the drug: the "clonidine withdrawal syndrome” is characterised in extreme cases by sweating, trembling, rapid heart beat and a dangerous rise in blood pressure.The symptoms may occur after only one or two missed doses or even after gradual withdrawal over 3 days.

Attempts to replicate the condition in dogs and cats produced inconsistent results (3) whilst in the rat "..attempts to reproduce the clonidine discontinuation syndrome...have met with even more difficulties and controversy than those encountered in dogs and cats.”(4) 'Success' was only achieved when researchers implanted a special pump into the rat's body to maintain adequate levels of clonidine in the bloodstream prior to withdrawal.(4)

In view of its serious side-effects, the Drug and Therapeutics Bulletin considers clonidine obsolete for the treatment of high blood pressure.(5)


1) Drug & Therapeutics Bulletin, 1990, vol.28, 79-80.
2) A.S.Nies in Clinical Pharmacology: Basic Principles in Therapeutics, 2nd edition,
Eds. K.L.Melmon & H.F.Morrelli (MacMillan, 1978).
3) L.Hansson et al, American Heart Journal, 1973, vol.85, 605-610.
4) M.J.M.C. Thoolen et al, General Pharmacology, 1981, vol.l2, 303-308.
5) Drug & Therapeutics Bulletin, 1984, vol.22, 42-43.

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