Clinical evidence,mechanism, importance and management
Serum phenobarbital levels rose by about 30 % in 11 out of 27 children when given 0.5 mL of a whole virus influenza vaccine USP,types A and B, (Squibb). Levels remained elevated 28 days after vaccination (See reference number 1).
It was suggested that vaccine inhibits liver enzymes concerned with metabolism of phenobarbital, thereby reducing its loss from body. Information is very limited. Note that, a similar 30 % increase in phenobarbital levels with felbamate has eventually required a dosage adjustment; however with this interaction increase will eventually be self-limiting. Therefore it seems unlikely that this moderate increase in phenobarbital levels will be of clinical significance..
1. Jann MW,Fidone GS. Effect of influenza vaccine on serum anticonvulsant concentrations. Clin Pharm (1986) 5, 817–20.