Hello thanks for asking from HCM Phenytoin is a good anti-convulsant drug and your father is taking 375 mg per day. The drug is known to cause side effects like rash, gum hypertrophy, lymph node enlargement, itching etc. So most likely the itching and rash your father is suffering is due to phenytoin. So this is the reason his doctor has advised to reduce the doses. Keppra is Levetiracetam. The drug is also an anti epileptic drug. The drug can be given with phenytoin and its safe to increase the dose of Keppra while on phenytoin. Taper the doses of phenytoin as per prescription given you you by his doctor. Thanks, hope this helps you.