The most prominent mechanism of action of lamotrigine is:
B. Lamotrigine is an anticonvulsant increasingly being used to prevent recurrent depressive episodes in bipolar disorder. Lamotrigine is thought to act via blockade of voltage-sensitive sodium channels, with secondary effect on calcium transport. Lamotrigine has weak effects on the serotonin system.
Reference:
The ECG changes produced by long-term lithium therapy mimic which one of the following electrolyte disturbances?
B. Lithium produces hypokalaemia-like changes on the electrocardiogram (ECG). This is related to displacement of intracellular potassium by the lithium ion. T-wave flattening or inversion is the commonest ECG change reported. These changes commonly disappear after stopping lithium. Lithium depresses the sinoatrial node; this can lead to sinus dysrhythmia, heart block, and syncope. Hence lithium is contraindicated in persons with sick sinus syndrome. Cardiac effects of lithium are more pronounced in those who have pre-existing cardiac problems, on diuretic treatment, and in those with renal impairment.
A 34-year-old lady with bipolar disorder responds well to lamotrigine. She develops a minor maculopapular rash 6 months after the onset of treatment. The most appropriate line of action is:
A. Lamotrigine is associated with rash, which is benign in about 8% of patients started on lamotrigine within the fi rst 4 months of treatment. In a small but significant proportion of patients (nearly 0.1%) this may be an early manifestation of Stevens–Johnson syndrome or toxic epidermal necrolysis. So lamotrigine must be discontinued whenever a rash is reported during treatment. Unfortunately, this discontinuation is not always sufficient to prevent the life threatening-hypersensitivity reaction, Steven–Johnson syndrome. The chances of developing a rash increases if lamotrigine is started at a higher than recommended dose or titrated at a faster than recommended speed. Coadministration of valproate can also increase the incidence of rash.
ECT is widely used to treat resistant and psychotic depression.
Which of the following statements is correct with respect to the clinical use of ECT?
A. The electrical stimulus delivered via ECT must be strong enough to reach the seizure threshold of the patient. Each individual has a different seizure threshold with nearly 40-fold variability among patients. During the course of ECT treatment itself, the seizure threshold could increase in the range of 25 to 200%. Older men generally have a higher threshold than the young. Amnesia related to ECT is proportional to the degree to which the administered electricity dose is high in relation to patients’ seizure thresholds. Incidence of cognitive disturbance is higher when a patient receives thrice-weekly ECT compared to twice-weekly treatments.
Which one of the following antidepressants resembles amphetamine in chemical structure?
B. Bupropion resembles amphetamine in its structure—it is a monocyclic aminoketone. Bupropion is a norepinephrine and dopamine reuptake inhibitor. Its side-effects profile is different from that of SSRIs in that it causes very low incidence of sexual dysfunction or sedation and produces some weight loss. It does not cause significant discontinuation reactions. It is currently licensed to help people quit smoking, but is not licensed as an antidepressant in the UK. Bupropion is contraindicated in patients with a history of eating disorder; it can cause significant changes in appetite. Bupropion has a high propensity to cause seizures.
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