All the following are used in the treatment of bipolar disorder except:
Ans: A (Gabapentin) Ref: Synopsis of Psychiatry. Kaplan & Sadock, 10th edition Explanation: Bipolar disorder (BPD) is a psychiatric disorder characterized by the occurrence of one or more episodes of mania with (usually) or without (rarely) depressive episodes. Both poles of mood disturbance occur in the same patient. It is characterized by two phases- illness phase & remission phase. In the illness phase patient may have either mania or depression or a mixed picture. The genetic component of this illness is high compared to unipolar depression (Note- there is no unipolar mania since even a single episode is construed as bipolar disorder). There are many subtypes like Bipolar I (mania + depression). Bipolar II (hypomania + depression) etc. The primary drugs for BPAD are "Mood Stabilizers"'. Lithium, Valproate, Carbamazepine are the first line drugs Oxcarbazepine, Lamotrigine, Levetiracetam are second-line drugs. Some atypical antipsychotics like Olanzapine, Quetiapine too have mood stabilizing property and often used alone in some cases. Lithium It is the first MS studied and one of the two drugs (the other one is Clozapine) proved to prevent suicide effectively. It is neither protein bound nor metabolized in the body & excreted unchanged in urine. The mechanism of action is inhibition of GSK3B & inositol phosphatase enzymes. Side effects are diabetes insipidus, hypothyroidism. seizures. Ebstein's anomaly (teratogenic). Useful in seborrheic dermatitis & leucopenia. Prophylactic blood level - 0.4-0.8 Meq/L Therapeutic blood level - 0.6-1.2 Meq/L Toxic level - > 1.2 Meq/L (the commonest first symptom of toxicity is coarse tremors & level above 1.8 Meq/L is the indication for hemodialysis) Valproate is a rapidly acting MS. (DOC for rapid cyclers - > 4 episodes per year) with multiple mechanisms (blockade of voltage-gated sodium channels, inhibition of GABA transaminase). It causes hemorrhagic pancreatitis, hepatic necrosis, hyperammonemia, midline defects (teratogenic). Carbamazepine is known to cause agranulocytosis, Steven-Johnson's syndrome, SIADH and often aggravates absence seizures & juvenile myoclonic epilepsy. Gabapentin is useful in "pain syndromes" & adjuvant to treat anxiety disorders.
Gabapentin
Valproate
Lithium
Carbamazepine
Bipolar Disorder