Carbamazepine may be prescribed to individuals diagnosed with bipolar disorder who are unresponsive to Lithium or who have four or more 'episodes' of distress in a year (rapid cycling bipolar). It is also prescribed for the treatment of epilepsy and trigeminal neuralgia (a type of facial pain).
Carbamazepines mechanism of action in psychiatric disorders is not fully understood. It's usefulness in the treatment of epilepsy results from lowering the threshhold at which a neuron is able to generate an impulse, fire and release neurotransmitters. It is thought to do this by inhibiting benzodiazepine receptors. Theoretically, if there was a region of the brain that regulated mood, inhibiting these neurons from firing and releasing neurotrasmitter might aid in mood regulation. Carbamazepine is also able to inhibit adrenergic receptors, which are activate by noradrenaline/adrenaline. In doing this it would cause a rise in noradrenaline, a chemical which has been implicated as being deficient in depression, thus Carbamazepines anti-depressant effects. Carbamazepine is also able to block sodium channels, increase the expression of other adrenergic receptors and decrease calcium flow into cells, though how these effects are linked to mood stabilisation are unknown.
Carbamazepine: Adult max = 1.6g daily, usual range 400-600 mg daily
Nausea and vomiting, dizziness, drowsiness, headache, confusion and agitation, double vision; constipation or diarrhoea, loss of appetite, rashes, reduced levels of white blood cells, reduced levels of platelets in the blood, anaemia, jaundice, hepatitis (inflammation of the liver), acute renal failure, severe skin reactions, hair loss, increased risk of clot formation, aches in the joints, fever, protein in the urine, lymph node enlargement, cardiac conduction disturbances (sometimes arrhythmias), disorders of movement, abnormal spontaneously occurring tingling or sensations of numbness, depression, impotence (and impaired fertility), enlargement of the breasts, milk production and secretion of the breasts, aggression, photosensitivity, low body sodium, oedema (swellings resulting from collections of fluid), irritation of the lungs, disturbances of bone metabolism.
When discussing coming off psychiatric drugs the terms withdrawal and discontinuation will be used interchangeably.
There are limited studies looking at the effects of withdrawal/discontinuation of Carbamazepine. Those that do are looking at whether there is an increased frequency of seizures in those who take Carbamazepine for epilepsy. There has been one study published looking at whether Carbamazepine withdrawal results in a 're-bound' mania, similar to the effects of Lithium withdrawal, however the study numbers were small. All six individuals included in the study had a diagnosis of bipolar disorder, were taking carbamazepine and had been 'well' for at least six months prior to discontinuing carbamazepine. What the study doesn't clarify is how fast the individuals discontinued the carbamazepine, whether they stopped all at once or reduced gradually over a period of weeks. In the study none of the individuals had a manic episode within 3 months of carbamazepine discontinuation, one individual became 'moderately' depressed. The full study can be viewed at the following link;
Macritchie KAN and Hunt NJ. Does 'rebound mania' occur after stopping carbamazepine?: A pilot study. /J Psychopharmacol/ 2000; 14:266
As with all psychiatric drugs we suggest an approach of better safe than sorry. The trends tend to suggest that coming off drugs all at once can be dangerous and that individuals are more likely to develop withdrawal symptoms if this approach is taken, as the brain doesn't have time to adapt to the absence of a drug it has become used to. The slower the withdrawal, the less likely an individual is to run into difficulties. We would recommend that individuals coming off carbamazepine, do so by gradually reducing the dose over a period of time and allow at least two weeks pass between each dose reduction.
As for how much to reduce by at a time, this is not a finite science. We would recommend that the maximum a dose should be reduced by is 25% every two weeks, this would mean it would take an individual approximately 2 months to fully come off carbamazepine. But the aim is not to come off quickly, it is to come off safely, with as little inconvenience as possible.
Example
So if an individual wished to come off carbamazepine and they were currently taking 600mg daily, the first two weeks they would reduce to 450mg, the next two weeks 300mg, the next two weeks 150mg etc. For other psychiatric medications some individuals have struggled with the last stages of withdrawal e.g. from 150mg to 0mg. Therefore you could reduce the last doses in smaller increments e.g. 100mg for a week, then 50 mg for a week etc. But everyone is different and you will be able to taper your withdrawal to your own needs.
Carbamazepine is also available in liquid form, which will enable you to reduce at a very gradual pace should you choose to reduce the rate of your reduction.
If you are taking any medications other than your psychiatric drugs it is worthwhile speaking to your GP about what potential interactions your psychiatric medications may have with your other medications.