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Ask the Experts


Because of weight gain, blood samples can no longer be taken to ensure the safe use of clozapine for the mental health of my son. What can be done for him, as clozapine appears to be the only medication that works for him?

Answered by: L. Fredrick Jarskog

Clozapine has long been known as a uniquely effective antipsychotic medication for many patients with schizophrenia and related psychotic disorders. This fact was recently emphasized in an article published online last week in The Lancet by Tiihonen et al. This study that showed that overall mortality rates in patients with schizophrenia treated with clozapine were lower than for any other antipsychotic medication. This occurred despite the fact that patients who receive clozapine usually have more severe, "treatment-resistant" forms of psychosis and often have a number of comorbid medical problems, some of which may be related to clozapine, such as obesity, diabetes, and cardiovascular disease.

In other words, despite all of its side-effects, clozapine remains the most effective antipsychotic for many patients and it may be the only treatment that really works. In those situations, all efforts must be made to circumvent barriers to continued treatment.

To minimize the potentially fatal risk of agranulocytosis (the loss of a type of white blood cell required to fight infection), patients treated with clozapine need to have regular monitoring of their white blood cell count. The frequency of this monitoring is weekly for the first 6 months of clozapine treatment, then every 2 weeks for 6 months and then every 4 weeks after that, assuming that the white blood cell count has not declined below a certain threshold during this period.

Because of obesity associated with clozapine treatment, regular blood draws can become challenging. Veins can become difficult to see and feel and larger veins may run deeply under the subcutaneous fat tissue. Nevertheless, experienced phlebotomists can almost always manage to draw blood from obese patients. To find experienced phlebotomists, it is helpful to go to a clinic that serves many patients, preferably a clinic associated with a tertiary care hospital.

There are other patient groups for whom blood draws can also be challenging, such as those with cancer, dehydration, or malnutrition, and the elderly. Phlebotomists experienced with many different types of patient groups will usually be most able to draw blood successfully under any circumstance. In some cases, portable ultrasound machines can be used to localize veins. Very rarely, it may be useful to obtain a consultation from an oncologist/hematologist who is very experienced in treating cancer patients for whom venous access is not only very difficult but also essential.

Your son's psychiatrist should be able to help identify someone who could provide such a consultation. Clearly, it is of utmost importance that your son continue to receive clozapine.