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Pharmacology

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CNS Part-1

Question
17 out of 58
 

Most effective drug for myoclonic seizures (LQ)



A Sodium valproate
B Zonisamide

C Carbamazepine
D Ethosuximide

Ans. A Sodium valproate

a. Sodium valproate is a commonly used anticonvulsant and is also a useful mood stabilizer and anti-migraine drug

b. The drug is GABAergic by nature and also inhibits T currents in thalamus. It is well absorbed orally and undergoes metabolism by a non CYP enzyme isoform. It is a short acting drug, therefore, multiple daily administration are needed.

c. It is the broadest spectrum and most efficacious antiepileptiC. It has been the drug of choice for generalized tonic clonic seizures, myoclonic, mixed, absence seizures of atypical types. The drug also has good efficacy in reflex seizures.

d. Most common side effect is gastrointestinal upset. It also causes tremors, weight gain, alopecia, increase in liver enzymes, thrombocytopenia, and polycystic ovarian disease.

e. Fatal hepatitis occurs in young babies. Maximum incidence is at 4th month of age. The drug is therefore, avoided in young babies.

f. Valproate is an enzyme inhibitor and can increase plasma levels of many drugs.

g. Zonisamide is a sulphonamide drug and has been used for generalized seizures, partial seizures, Lennox-Gestaut syndrome and infantile spasm.

h. The drug is being investigated for a number of clinical indications e.g. Parkinson’s disease, bipolar disorders etC. it may act like carbonic anhydrase or Na+ channel blockers.

i. Sedation and dizziness can occur as side effects apart from sulpha allergy that is occasional (BG Katzung’ 10th Edition, 2010).

j. Carbamazepine is an iminostilbene derivative related structurally to TCAs. The drug acts similar to that of phenytoin and is well absorbed orally. It forms an active and a toxic metabolite named 10,11 epoxide. Majority of side effects occur due to this. The drug is an auto inducer and is the drug of choice for neuralgias and partial seizures including psychomotor epilepsies. Side effects include rashes, hepatitis, neutropenia and SIADH. Phenytoin like side effects such as diplopia, nystagmus and ataxia can also occur. Dextropropoxyphene can inhibit its metabolism causing toxicity.

k. Ethosuximide is a succinimide and blocks T currents in thalamus. The drug is well absorbed and is long acting. It is not metabolized and is the drug of choice for absence seizures. GI upset and thrombocytopenia are side effects.

Carbamazepine

Drug interactions


a. OCP failure

b. Phenytoin induced metabolism of valproate

c. Valproate displaces phenytoin from protein binding site

d. Carbamazepine

e. Sulfonamides


Use


a. Partial


b. epilepsy (Temporal lobe epilepsy)

c. Neuralgias (All types)

d. Use gabapentin


e. in refractory cases


Side of Carbamazepine


a. MC-


b. rashes

c. Hepatitis

d. Neutropenia

e. SIADH (Dilutional hyponatremia)

f. Rx-demeclocycline


(Mnemonics: Carbamazepine and phenytoin can aggravate myoclonic epilepsy)

CNS Part-1 Flashcard List

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