Carbamazepine, Lamotrigine,phenytoin And Topiramate

Question 1

Carbamazepine

Answer 1

• it is the drug choice of simple and complex focal seizures
• first line option for the generalisedtonic cloning seizures
• start a low dose and build up slowly
• Indiactions are - Focal and generalised - Tonic clonic seizures, diabetic neuropathy, prophylaxis of bipolar and cute alcohol withdrawal
• Avoid Carbamazepine and oxacarbazipine in absence,tonic, a tonic and myclonic (may exacerbate symptom)
  Stick to the same brand of carbamazepine - different preps of oral have different bioavailibilities

Question 2

Carbamazepines Patient and carers advice

Answer 2

Can cause blood,hepatic and skin disorders - seek medical attention if there is a fever,rash,sore throat, mouth ulcer,bruising or bleeding

Question 3

Carbamazepine therapeutic index

Answer 3

Optimum response 4-12 mg/l (20-50 micromol/L) measured after 1-2 weeks

Question 4

Side effects for carbamazepines

Answer 4

Hyponatraemia
Ataxia
Nystagmus
Drowsiness
Blurred Vision
Arrhythmias
Gi (NAND V)
More side effects are common at the start of treatment are dose related and can be reduced by modified release preps

Question 5

Carbamazepine pre treatment screening

Answer 5

• Test for HLA-B1502 allele in Han Chinese or Thai origin - increased risk of Steven’s-Johnson syndrome
• This risk of SJS found mainly in Han Chinese and Thai poulations
• Avoid unless no alternative

Question 6

Lamotrigine main points:

Answer 6

• Can cause serious skin reactions (esp in kids) most rashes occur in 8 weeks especially with children
• Indications - Focal seizures,secondary generalised tonic clonic seizures, bipolar disorder
• serious skin reactions including Steven’s Johnson syndrome(serious skin reaction)
• Valporate increases plasma Lamotrigine conc and inducers will reduce it
  -counselling - withdraw if rash of hypersensitivity develops and see your Gp
• SIGNS OF BLOOD DISORDERS TOO

Question 7

Phenytoin Key points -

Answer 7

Narrow therapeutic index
- indication - tonic clonic seizures and focal seizures

-preparations containing phenytoin sodium (capsules and injections) are not bio equivalent to those containing phenytoin base (eg.equatin suspension)(100mg of phenytoin sodium is equivalent to 92mg phenytoin base) Base = suspension and phenytoin sodium = capsule and injections
- care is needed when you are switching between formulations and plasma phenytoin concentration monitoring is recommended.

Question 8

MHRA Warning for phenytoin

Answer 8

Risk of suicidal thought and behaviour - risk of death and severe harm with injectable phenytoin - maintain pts on the same brand

Caution with intramuscular phenytoin sodium- should not be used ( absorption is slow and erratic). Use Iv route, consider vitamin D for patients that are immobilised for a along period of time or inadequate sun exposure or dietary calcium intake

Question 9

Phenytoin target range

Answer 9

• 10-20 mg/L (40-80 micromol/l) PHENYYYY TEENN

Question 10

Phenytoin toxicity

Answer 10

Nystagmus(involuntary eye movements), slurred speech, ataxia, confusion and hyperglycaemia

• discontinue if rash develops
• blood and skin disorders - seek medical attention if signs of blood disorders eg. Fever,rash, malaise, bruising and infection

Question 11

Phenytoin (enzyme inducer) - serious interactions?

Answer 11

• Amiodarone - increases the concentration of phenytoin
• Apixaban,dabigatran,edoxaban,rivaroxaban - phenytoin increases exposure to apixaban (use with caution or just avoid)
• Bupropion and Buspirone - Phenytoin decreases exposure
• Carbamazepine - Phenytoin decreases concentration of carbamazepine
• Ciclosporin - Phenytoin decreases the concentration of ciclosporin
• Combined hormonal contraceptives and desogesterel, levonorgestrel,ulipristal - phenytoin decreases efficacy
  Miconazole- increases risk of phenytoin toxicity
• Valporate - affects conc of phenytoin and phenytoin decreases conc of valporate

Question 12

Inducer does what

Answer 12

Induces the break down of a drug that it is interaction with

So inducer and inhibitor — it will increase the concentration

Question 14

Side effects of phenytoin

Answer 14

P- 45 inducer
Hirsutism
Enlarged Gums (Gingival hyperplasia)
Nystagmus and other signs ( ataxia,vertigo diplopia)
Teratogenicity
Osteopenia
Interferes with folic acid
Neuropathy

Question 15

Topiramate

Answer 15

Indication - generalised tonic clonic seizures or focal seizures
Myopia with secondary angle - closure glaucoma
Within 1 month of starting
- report any visual issues
- seek specialist advice if raised intra-ocular pressure occurs
- Cautionary label - Label 8 don not stop taking unless doctor tells you to stop, Label 3: May make you drowsy - if that happens do not drive or use tools or machines

Question 16

Ethosuxamide

Answer 16

First line treatment for absence seizures, Also licensed for myoclonic seizures. REPORT SIGNS OF BONE MARROW DEPRESSION!!!

Question 17

Clobazam

Answer 17

Prescription for epilepsy has to be Endorsed with SLS

Question 18

Gabapentin

Answer 18

MHRA WARNING - Risk of severe respiratory depression even without concomitant opioid medicines - adjust does in patients with respiratory problems.

Reclassified CD3 drug due to risk of abuse, Observe patients for signs of abuse and dependence 0 inform them of risk of interactions with alcohol and meds which cause CNS depression especially opioids