8(e) Seizure: medications -
Dilantin (phenytoin) and others
Not all brain tumour patients will be prescribed anti-seizure medication. It will be prescribed if seizure is an early symptom, or if it occurs after operation of if the doctor thinks seizure very likely. But if it not prescribed and there is no seizure, excellent.
The drug phenytoin, marketed as Dilantin, is a long established, generally very effective and reliable anti-seizure medication.
Some doctors may prescribe a different drug from the start, something with which they are familiar, some patients may have a reaction to Dilantin or it may not be effective and a substitute may be needed from the outset, some patients may need to be moved to a different drug if after a period of protection from seizure, Dilantin ceases to provide protection. But most patients will start out with Dilantin.
Taking Dilantin over a period of time involves some management. There are a number of interactions with other drugs and substances. For information on Dilantin's interactions, this site is useful.
There is in particular an interaction with dexamethasone. When you take dex, the processes of metabolism in the liver which break down Dilantin, rendering it inactive, are speeded up, so an increase in dexamethasone dose may lower serum Dilantin levels. On the one hand, raising the dex dose may have a benefit in reducing prospect of seizure if it reduces swelling significantly — but on the other, if it eats away at the level of Dilantin in the blood, and that serum level is not monitored and maintained, the lowered serum level of Dilantin can lead to seizure.
This need to monitor and adjust 'serum Dilantin' is complicated by the fact that once an effective level of Dilantin is established in the blood, very small dose adjustments can cause significant swings in serum level.
Anecdotal accounts to brain tumour discussion groups suggest that a lot of seizures in brain tumour patients, after diagnosis, arise from poor management of anti-seizure medication. Why risk seizure? — make sure serum levels of anti-seizure medication are kept at a sensible and safe levels, by apprpriately frequent monitoring.
There is also some prospect, unfortunately, that changes in social activity can trigger seizure — excitement, pleasure, upset — so you really do want to try to have the best level of medication protection, rather than avoid pleasure or excitement!
There are some negative effects of Dilantin overdose. The biggest risk of this occurring on a serious scale if a patient is being given emergency treatment with IV Dilantin, say at different hospitals — if you are away from home and regular doctor access, for example, and perhaps the person having seizure problems is transferred between hospitals. If you are travelling away from access to your treating doctor or hospital, make sure you have a piece of paper with your treating doctor's phone number, or the hospital file number, on hand, along with a record of drug treatments. This may sound obsessive, but it is unfair to expect doctors who may be junior and inexperienced, who spend most of their time dealing with road or other trauma in emergency, to have an immediate genius in dealing with a brain tumour seizure circumstance — the carer knows the case and can if organised provide a brief.
Leaving aside sudden major change in serum Dilantin level in such a crisis, the serum level can drift up gently in various circumstances. The most readily observed symptoms are drowsiness, vagueness, odd eye movements and red spotty skin rash. Drowsiness can indicate other problems when dealing with brain tumour as well. Worth consulting the doctor in any such circumstances.
There is a good site with useful information on Dilantin overdose here.