Unlike the problem with some antidepressants, if you are very thirsty due to taking Lithium, a different mechanism is taking place.  Lithium reduces the capacity of your kidney to retain fluid, so that it causes you to pass a lot of urine.  In an attempt to compensate for this excessive loss of fluid from your body, you become very thirsty.  The thirst on Lithium can become severe, so that people have to drink large amounts of fluid day and night, and perhaps carry fluid with them continuously throughout the day.


There is an unusual antidote for this problem with Lithium.  This involves taking a tablet which would make people not taking Lithium actually lose fluid!  Particular diuretics (tablets which cause fluid loss) have the reverse effect in people taking Lithium.  These diuretics are in the group of diuretics, known chemically as the “thiazide diuretics”.  Chlorthiazide is the best known member of this group.


It is calculated that Chlorthiazide will reduce fluid loss in people taking Lithium by twenty five per cent.  This markedly reduces the amount of urine you pass, and therefore the amount of fluid you need to drink to compensate.  You may have to experiment as to whether it suits you better to take the thiazide diuretic at night or in the morning, to give you the best control of day time thirst and night time disturbance.


However, you must also remember that losing less fluid also means you will lose less Lithium, and your blood levels of Lithium will increase if you take thiazide diuretics.  Accordingly, the usual practice is to reduce your Lithium dose when adding in thiazide diuretics.  Your doctor will keep a check on your Lithium levels until the correct mixture of Lithium and thiazide diuretic is established, and presumably will also keep an eye on your potassium levels, which may be lowered due to taking the diuretic.


This information is intended to improve your knowledge of the treatment you are receiving.  Any further points can be discussed at your next consultation with your doctor.


Important Disclaimer:  This site is medical information only, and is not to be taken as diagnosis, advice or treatment, which can only be decided by your own doctor.

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