Hyperinsulinism is caused by many different genetic defects. The following are the three most important in relation to Diazoxide.
The most common form of hyperinsulinism is caused by a defect in the potassium channel (KATP channel). In many cases this channel is missing and in other cases it is there but not functioning properly. Diazoxide acts on this channel to prevent insulin release. Therefore, in cases where this channel is missing, Diazoxide will not work.
In cases where the channel is present but not functioning properly, Diazoxide may work a little or not at all.
The second most common cause of hyperinsulinism is the hyperinsulinism/hyperammonemia syndrome, in which the gene defect has nothing to do with the potassium channel, but instead interferes with the metabolism of glutamate in the cell, causing excessive insulin secretion. Children with this syndrome all have normal potassium channels and thus Diazoxide works on this channel and prevents insulin secretion.
As a result, most patients with glutamate dehydrogenase hyperinsulinism will be responsive to Diazoxide.
The third type of hyperinsulinism, which is extremely rare, is glucokinase hyperinsulinism. In this condition the potassium channel is also functioning normally but the defect is at another site in the cell. Therefore, in this condition, Diazoxide, by acting through the potassium channel, works very well to prevent hypoglycemia.
Diazoxide is an oral medication that can be given anywhere from q day to tid. The dose is generally prescribed based on body weight and ranges from 5-15 mg/kg/day. As the dose gets higher, the side effects of the drug become greater. The main side effects are initially fluid retention (increased swelling of the feet, hands, and face), increased weight gain from excessive water being stored in the body and in small infants, this can cause heart failure due to fluid overload.
A later side effect is the increased growth of hair on the body including not only the head, but also on the face, arms, legs, and back. This is not a sexual type of hair (pubic hair or underarm hair), but rather an increase in the normal body hair found in all infants and children. Many parents find this increased hair growth a nuisance and many will use different methods to get rid of the hair, such as shaving, etc.
Like all drugs, Diazoxide may cause an unpredictable allergic reaction consisting of skin rashes or a more serious allergic reaction. It can also cause a decrease in the blood count. Finally, some children experience nausea, and loss of appetite.
Overall, Diazoxide is a very serious drug and when effective, it usually works extremely well.
Most children, who start on diazoxide and in whom it works very well, will be on it for many years. However the dose is not always increased as the child gets bigger. This is something that the individual physician looking after the child will decide based on blood glucose control.
More information on the different types of hyperinsulinism.