Influence of Valproic Acid on Extinction-based Therapy in Patients With Fear of Spiders.

Inclusion Criteria: * DSM-IV diagnosis of specific phobia (animal type: spider) * BAT score (at screening) between 1 and 7 points * Physically healthy * Normotensive (90/60-140/90 mmHg) * Male or female * Aged between 18 and 40 years * Native or fluent German-speaking * Females have to be on effective birth control Exclusion Criteria: * Other axis I disorder except a further comorbid phobic disorder * Concurrent psychotherapy or pharmacotherapy * Previous exposure-based therapy for specific phobia * Parallel participation in another study * Body weight less than 50kg * Long-term medication intake * Substance abuse * 5 or more cigarettes a day and/or inability of being abstinent for at least 5 hours * Pregnancy or breast-feeding * Kinetosis * History of coagulation disease * History of gastrointestinal disease * Laboratory exclusion criteria: clinically relevant deviation of laboratory values (blood count, blood chemistry, coagulation status, liver and pancreas enzymes, electrolytes) from normal range