Noradrenaline |
| Stimulant medications increase release and inhibit reuptake of norepinephrine(5,6). Clonidine which is most effective in treating the hyperaroused/aggressive behavior of AD/HD is an alpha-2 noradrenergic agonist(10).A number of other drugs effective in the treatment of AD/HD alter noradrenergic turnover.
3-methoxy-4-hydroxyphenylglycol (MHPG) is a noradrenergic metabolite and can be measured in the urine of children with AD/HD to assess changes in noradrenergic function in response to medication. A number of drugs which are effective in treating AD/HD alter urinary MHPG levels. Dextroamphetamine reduces urinary excretion of MHPG (11-14). Desipramine, a tricyclic antidepressant which is moderately efficacious in amelioration of AD/HD symptoms, also reduces urinary MHPG(15). Behavioral-biochemical correlative data with tricyclic antidepressants and monoamine oxidase inhibitors show a correlation between a change in urinary noradrenergic metabolites and clinical response. However, trials with fenfluramine have shown a large decrease in urine MHPG levels but no clinical effect(16). Thus a change in noradrenergic function appears to be a necessary but not sufficient condition for improvement of AD/HD symptoms. |