[Can treatment associated with ticlopidine and nifedipine increase serum levels of phenobarbital?].
BACKGROUND
We report a case in which the association between ticlopidine, nifedipine and phenobarbital was linked with a higher than expected phenobarbital concentration in serum, which suggested a possible interaction between these drugs.


METHODS
A 67 year old male who received treatment with phenobarbital, digoxin, nifedipine, ticlopidine, paroxetine and clorazepate dipotassium. The first control of the level of phenobarbital in serum was performed without any symptoms or signs of toxicity or ineffectiveness. A phenobarbital concentration in serum of 21.4 mg/L was obtained, with a serum level/dosage ratio of 16.7.


CONCLUSIONS
The serum level/dosage ratio of phenobarbital that was found in this case is almost twice as high as expected. In the absence of other factors that can explain this finding, we believe that two drugs (ticlopidine and nifedipine) may be involved in an interaction with phenobarbital.


CONCLUSIONS
The high value of the serum level/dosage ratio that was found makes it advisable to monitor the concentrations of phenobarbital in serum in treatment associated with ticlopidine or nifedipine, especially when adjusting the dosage, beginning or ending treatment with these drugs.
Sánchez-Romero
A
A
Complejo Hospitalario Universitario de Albacete, Albacete, España. asanchez@hgab.insalud.es
García-Delgado
R
R
Durán-Quintana
J A
JA
D000368:Aged; D002121:Calcium Channel Blockers / Q000378:metabolism* / Q000627:therapeutic use; D004347:Drug Interactions; D006801:Humans; D006993:Hypnotics and Sedatives / Q000097:blood* / Q000627:therapeutic use; D008297:Male; D009543:Nifedipine / Q000378:metabolism* / Q000627:therapeutic use; D010634:Phenobarbital / Q000097:blood* / Q000627:therapeutic use; D010975:Platelet Aggregation Inhibitors / Q000378:metabolism* / Q000627:therapeutic use; D013988:Ticlopidine / Q000378:metabolism* / Q000627:therapeutic use
D002121:Calcium Channel Blockers; D006993:Hypnotics and Sedatives; D010975:Platelet Aggregation Inhibitors; D009543:Nifedipine; D013988:Ticlopidine; D010634:Phenobarbital