Paediatric Psychopharmacology

Psychotropic drug is to be given to either young or elderly patient, the general rule was to start with the lowest dose that is therapeutically beneficial in contrast to the standard dose that would be given to an adult. The rates of drug absorption, metabolism and distribution may differ. In the case of the child and aged one, hepatic microsomal enzyme metabolism, which is largely responsible for the metabolism of psychotropic drugs, were suboptimal.
There is also evidence that tissue sensitivity to many psychotropic drugs is altered at the extremes of age. Thus the general rule is to start at the lowest possible dose and, if necessary, increase the dose slowly until optimal therapeutic benefit is achieved. In the treatment of psychiatric disorders of children, the clinician is faced with a problem which is less apparent in the adult patient. In adult psychiatry, the diagnosis of the condition assists in ensuring optimal treatment.
As psychiatric diagnosis of childhood disorders is at a more elementary stage than it is in adult psychiatry, the diagnostic approach to treatment still leaves much to be desired. This chapter will therefore be confined to a discussion of those disorders of childhood for which there seems to be reasonable agreement over diagnosis and treatment. Despite the success in the use of psychotropic drugs for the treatment of psychiatric disorders in adults, and to some extent in adolescents, the application of psychotropic drugs for the treatment of children has been less encouraging. This has been due to the use of invalid diagnostic classifications, limitation of the methods for measuring response to treatment and the utilization of concepts drawn from adult psychiatry being inappropriately applied to children. These difficulties are reflected in the greater variability in the use of psychotropic drugs in children. This unfortunate situation is reflected in the fact that methylphenidate, imipramine and chlorpromazine still form the bulk of the prescriptions of child psychiatrists.There are four main areas where psychotropic drugs are useful in children:

1. To provide relief from symptoms until the child matures, for example, in enuresis.

2. As an adjunct to other treatments as, for example, when a child refuses to attend school.

3. To suppress symptoms and thereby prevent the negative effects on other psychogical parameters. An example of this would be a child who suffers from tic disorders which causes embarrassment.

4. In severe conduct disorders when other non-drug-based methods have been unsuccessful.

Short-term side effects of psychotropic drugs

As with all types of medication, the side effects of psychotropic drugs should be weighed against their benefits. Symptoms such as dizziness, appetite suppression and sleep disturbance occur quite commonly but often diminish following continual use. Other more serious side effects may involve changes in endocrine and cardiac function, effects which can sometimes be controlled by reducing the drug dose. Finally there are idiosyncratic and allergic reactions such as agranulocytosis which are difficult to predict and which can be fatal in some cases. Other side effects may only be manifest in the behaviour of individual patients. For example, benzodiazepines have a calming effect in most cases but can occasionally be associated with behavioural dysinhibition and lead to aggressiveness in a disturbed child. Similarly, neuroleptics can suppress aggression but also cause emotional flattening and cognitive dysfunction. Such side effects are particularly important in the younger child. Longer-term side effects such as growth retardation as a result of stimulants and tardive dyskinesia following the prolonged use of typical neuroleptics are particularly important. It is presently unclear whether the long-term use of stimulants leads to dependence, although there would appear to be little evidence that this is the case.