Neurological Drugs

Question 1

What is carbidopa?

Answer 1

A peripheral decarboxylase inhibitor

Question 2

Why is Levodopa given with Carbidopa?

Answer 2

The carbidopa (decarboxylase inhibitor) reduces the peripheral conversion of L-Dopa to dopamine, reducing side-effects, and effective brain dopamine concentrations can be achieved with lower doses of levodopa

Question 3

What is the indication for using Levodopa (Carbidopa)

Answer 3

Parkinson’s Disease

Question 4

What is the clinical use of Levadopa?

Answer 4

Used in Parkinson’s disease

Effective against akinesia and rigidity rather than tremor.

Effectiveness diminishes over some months to a few years

Question 5

What are the contra-indications for using Levadopa (Carbidopa)?

Answer 5

Closed angle glaucoma

Drug induced Parkinsonism

Question 6

What are the possible side-effects of Levodopa (Carbidopa)?

Answer 6

Anorexia, Nausea, Vomiting
Postural hypotension
Acute schizophrenia-like syndrome
Confusion
Anxiety
Disorientation
Insomnia/nightmares

Question 7

What are the interactions of Levodopa?

Answer 7

Anaesthetics: ⬆️ risk of dysthymias
MAOIs: risk of hypertension crisis
Neuroleptics: block dopamine receptors

Question 8

What is levodopa

Answer 8

Dopamine precursor

Question 9

What is Carbamazepine?

Answer 9

It is an Anticonvulsant drug

It also relieves neuropathic pain

Question 10

What is the clinical use of Carbamazepine?

Answer 10

Partial and generalised seizures (tonic-clonic) but not absence seizures

Also neuropathic pain and bipolar disorder

Question 11

What is the method of action of Carbamazepine?

And how is it metabolised?

Answer 11

It works by blocking Na+ channels to inhibit action potential initiation and propagation.
Action is preferentially on rapidly firing neurons in e epileptic focus

It is metabolised by the P450 system in the liver

Question 12

What are the contra-indications for carbamazepine?

Answer 12

AV conduction abnormalities

History of bone marrow depression

Question 13

What are the interactions of carbamazepine?

Answer 13

Induces hepatic drug-metabolising enzymes (P450)

• cimetidine, erythromycin: inhibit metabolism of carbamazepine
• corticosteroids, cyclosporine, phenytoin: ⬇️ effector carbamazepine
• diltiazem, isoniazid, verapamil: ⬆️ plasma concentration of carbamazepine
• OCP: ⬇️ effect of OCP
• Warfarin: ⬇️ effects of warfarin

Question 14

What class of drug is phenytoin?

Answer 14

Anti- convulsant

Question 15

What is the mechanism of action of phenytoin?

Answer 15

Alters transmembrane movement of Na+/K+ by blocking voltage gated Na+ channels

Prevents spread of epileptic discharges

Question 16

What are the indications for Phenytoin?

Answer 16

Epilepsy (all except absence seizures)

Trigeminal neuralgia

Question 17

What are the cautions for Phenytoin?

Answer 17

Hepatic impairment

Pregnancy

Breast feeding

Question 18

What are the side effects of Phenytoin?

Answer 18

Common: dizziness, headache, confusion, insomnia, nausea, vomiting, hirsutism

Rare: gum hypertrophy, rash, Stevens-Johnson syndrome, drug induced SLE, blood dyscrasias

Question 19

What are the possible interactions of phenytoin?

Answer 19

Induces hepatic drug-metabolising enzymes (P450)

• amiodarone, aspirin, cimetidine, diltiazem, nifedipine: ⬆️ plasma concentration of phenytoin
• OCP: ⬆️ metabolism of OCP
• Rifampicin: ⬇️ plasma concentration of phenytoin
• Warfarin: ⬆️ metabolism of warfarin

Question 20

What class of drug is Sodium Valproate?

Answer 20

Anticonvulsant

Question 21

What is the mechanism of action of sodium valproate?

Answer 21

• ⬆️ GABA content of the brain by inhibiting GABA transaminase enzyme, preventing GABA reuptake
• ⬇️ concentration of aspartate, an excitatory neurotransmitter
• blocks voltage gated Na+ channels

Question 22

What are the indications for sodium valproate?

Answer 22

Epilepsy

Question 23

What are the contra-indications for sodium valproate?

Answer 23

Hepatic dysfunction (metabolised/excreted in the liver)

Porphyria

Question 24

What are the possible side-effects of sodium valproate?

Answer 24

Common: nausea, vomiting, weight gain

Rare: hepatic failure, pancreatitis, blood dyscrasias, sedation, transient hair loss

Question 25

What are the interactions of sodium valproate?

Answer 25

- Anticonvulsants: 2 or more together gives increased effects and sedation - Neuroleptics: decreases effects of sodium valproate - TCAs: decrease anticonvulsant effect of sodium valproate

Question 26

What class of drug is Lamotrigine?

Answer 26

Anticonvulsant

Question 27

What is the method of action of lamotrigine?

Answer 27

Inhibition of glutamate release decreases postsynaptic neuronal excitation. This may be due to Na+ channel inhibition in the nerve ending

Question 28

What are the indications for lamotrigine?

Answer 28

Partial seizures Primary/secondary generalised tonic-clonic seizures Lennox-Gastaut syndrome seizures Trigeminal neuralgia

Question 29

What are the cautions for lamotrigine?

Answer 29

Needs to be monitored for hypersensitivity

Question 30

What are the possible side-effects of lamotrigine?

Answer 30

``` Rash Hypersensitivity syndrome Nausea Vomiting Diarrhoea Hepatic dysfunction ```

Question 31

What class of drug is metoclopramide?

Answer 31

Anti-emetic (dopamine antagonist)

Question 32

What is the mechanism of action of metoclopramide?

Answer 32

- blocks dopamine receptors in chemoreceptors trigger zone in the brainstem - ⬆️ rate of gastric/duodenal emptying by relaxing pyloric sphincter - ⬆️ lower oesophageal sphincter tone

Question 33

What are the indications for metoclopramide?

Answer 33

Nausea and vomiting Gastro-oesophageal reflux

Question 34

What are the contra-indications for using metoclopramide?

Answer 34

Parkinsonism 1st 3-4 days after GI surgery Intestinal obstruction

Question 35

What are the possible side-effects of metoclopramide?

Answer 35

Common: acute dystonic reactions Rare: tardive dyskinesia, depression, galactorrhoea, cardiac conductive abnormalities, drowsiness, restlessness, diarrhoea

Question 36

What are the possible interactions with metoclopramide?

Answer 36

- Lithium: ⬆️ risk of extrapyramidal adverse effects | - NSAIDs: ⬆️ absorption of NSAIDs, therefore their effects are increased

Question 37

What are the side-effects of carbamazepine?

Answer 37

Drowsiness, headache, mental disorientation Liver damage, agranulocytosis, aplastic anaemia, skin reaction Teratogenic effects