Date post: | 07-Aug-2015 |
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NEWER ANTIEPILEPTIC DRUGS
OVERVIEWDr.Subhashis Sharma
Moderator
Dr.Anurag Jhanjee
Asst.Professor[Pschiatry]
OVERVIEW
Seizures are sudden episodes of neurological dysfunction caused by abnormal electrical activity of the brain
Seizures are common
10% of the population will have a seizure during their lifetime (about half are seizures with fever in infancy)
Epilepsy: recurrent, unprovoked seizures
SEIZURE TYPES
Primary Generalized Tonic-clonic (“grand mal”) Absence (“petit mal”) Myoclonic Tonic Atonic (“drop attacks”)
Partial Simple Complex Secondary generalized
“OLDER” AEDS
Phenobarbital 1912
Phenytoin 1938
Primidone 1952
Ethosuximide 1960
Carbamazepine 1974
Valproate 1978
Ethosuximide 1980
NEWER AEDS
Felbamate 1993
gabapentin 1994
Lamotrigine 1995
Topiramate 1996
Tiagabine 1998
Levetiracetam 1999
Oxcarbazepine 2000
Zonisamide 2000
Rufinamide 2004
Pregabalin 2005
Lacosamide 2008
Eslicarbazepine 2009
Retigabine 2011
MECHANISM OF ACTION OF DIFFERENT AEDS
CARBAMAZEPINE
First line drug for partial szs for years
Two long-acting forms now avail (2X/day)
Side effects at just above therapeutic range
Not effective for some seizure types
Must start slowly due to side effects
No IV form
Lots of interactions
PHENYTOIN
First line for partial seizures for years
Once a day
IV form
Side effects at just avove therapeutic range
Not effective for some seizure types
Side effects: imbalance, sedation, cognitive, gum problems, osteoporosis
Many interactions
VALPROATE
Works for all seizure types
Around for decades
Rare allergic reactions
Helps prevent migraines
New IV form
New long-acting form
Side effects, esp. weight gain & tremor
Menstrual irregularities
Not best for pregnancy
Significant drug interactions
BARBITURATES (PRIMIDONE AND PHENOBARBITAL)
Effective
Once a day (phenobarbital)
cheap
IV form (phenobarbital)
Sedation and cognitive effects
Withdrawal
OTHER OLD MEDICATIONS
Acetazolamide
Conazepam & lorazepam
Ethosuximide
Ketogenic diet
ACTH/steroids
NEWER AEDS
Equally effective as older AEDs
Most better tolerated than older AEDs
Most have fewer interactions with other medications than older AEDs
All expensive
GABAPENTIN
Binds to the α2-δ protein subunit of voltage-gated
calcium channels
This closes N and P/Q presynaptic calcium channels,
diminishing excessive neuronal activity
and neurotransmitter release
GABAPENTIN
Generic name: Gabapentin
Available as: Gabapentin: tablets 600mg, 800mg, capsules 100mg, 300mg, 400mg.
Average total daily dose: 900mg – 3600mg daily divided into 3 doses, up to 4800mg daily
Doses per day: 3
Treatment: Monotherapy and add-on therapy for focal seizures with or without secondary generalisation (where other treatment has not worked). May make myoclonic and absence seizures worse.
Most common possible side effects include the following:Rash. Diarrhoea, nausea, vomiting, dry mouth, appetite change, weight gain, high blood pressure, fluid retention, confusion, depression, sleep disturbance, headache, dizziness, anxiety, tremor, unsteadiness, flu-like symptoms, incontinence, impotence, and double vision.
GABAPENTIN
ADVANTAGES:.No interaction with other drugs
.Eextremely rare allergic reactions
.Can be started quickly
.Well tolerated
.Treats pain,anxiety,restless leg syndrome,pain due to diabetic neuropathy,post herpetic neuralgia,prophylactic for migraine.
DISADVANTAGES:.Three times a day dosing.
.Does not treat all types of seizures
LAMOTRIGINE
Carbamazepine like action profile
Prolongation of Na+ channel inactivation
And suppression of high frequency firing
In addition it may directly block voltage
sensitive Na+ channels thus stabilizing the
presynaptic membrane
And preventing release of excitatory neurotransmitters mainly glutamate and mainly glutamate & aspartate
This may account for broad spectrum of antiseizure
efficacy
LAMOTRIGINE
Generic name: Lamotrigine
Available as:tablets 25mg, 50mg, 100mg, 200mg, dispersible tablets 5mg, 25mg, 100mg.
Average total daily dose: Used alone: 100 – 200mg daily divided into 1 – 2 doses, up to 500mg.With sodium valproate: 100 – 200mg daily divided into 1 – 2 doses.With enzyme-inducing AEDs and without sodium valproate: 200 – 400mg daily divided into 1 – 2 doses, up to 700mg.Without enzyme-inducing AEDs and without sodium valproate: 100 – 200mg daily divided into 1 – 2 doses.
Doses per day: 1 – 2 Treatment: Monotherapy and add-on therapy for focal and generalised seizures. Also used for
seizures associated with Lennox-Gastaut syndrome.
Most common possible side effects include the following:Serious skin rash and hypersensitivity. Risk minimised with slow introduction. Nausea, vomiting, diarrhoea, dry mouth, aggression, agitation, headache, drowsiness, dizziness, tremor, difficulty sleeping, unsteadiness, back pain, joint pain, eye movements, double vision, and blurred vision.
LAMOTRIGINE
ADVANTAGES:
Minimal effect on other medications
Works for al types of Seizures
Very well Tolerated
Minimal sedation
Safe in pregnancy
Monotherapy
DISADVANTAGES:
Rashes if started quickly.Must start slowly
TOPIRAMATE
It appears to act by multiple mechanisms
Phenytoin like prolongation of Na+ channel inactivation
GABA potentiation by a postsynaptic effect and antagonism of certain glutamate receptors
TOPIRAMATE
Generic name: Topiramate
Available as:tablets 25mg, 50mg, 100mg, 200mg, capsules 15mg, 25mg, 50mg.
AVERAGE DAILY DOSE: Taken alone: 100mg daily (up to 18 years) or 100 – 200mg daily (over 18 years). Taken with other AEDs: 5 – 9mg/kg daily (up to 18 years) or 200 – 400mg daily (over 18 years). All divided into 2 doses.
Doses per day: 2 Treatment: Used for focal seizures with or without secondary generalisation and
tonic clonic seizures, where other treatment has not worked. Topiramate has a licence for monotherapy but is not widely used as a first line drug
Most common possible side effects include the following:Rash. Nausea, diarrhoea, vomiting, constipation, indigestion, abdominal pain, dry mouth, appetite changes, impaired attention, cognition and coordination, movement problems, tremor, drowsiness, dizziness, anxiety, confusion, mood changes, depression, irritability, and anaemia.
TOPIRAMATE
ADVANTAGES:
Minimal interaction
Probably works for all seizure types
Sprinkle form
Approved for monotherapy
Weight loss
Approved for migraine prevention
DISADVANTAGES: Cognitive side effects
½% renal stone
Tingling/pins & needles
Can decreases the efficacy of OCP
TIAGABINE
Potentiates GABA mediated neuronal inhibition
by depressing GABA transporter GAT-1
which removes synaptically released GABA
into neurons and glial cells
TIAGABINE
Generic name: Tiagabine
Available as:tablets 5mg, 10mg, 15mg.
Average total daily dose: With enzyme-inducing AEDs: 30 – 45mg daily divided into 2 – 3 doses. Without enzyme-inducing AEDs: 15 – 30mg daily divided into 2 – 3 doses.
Doses per day: 1 – 3
Treatment: Add-on therapy for focal seizures with or without secondary generalisation where other treatment has not worked. May make myoclonic seizures worse.
Most common possible side effects include the following. Report severe reactions, such as a skin rash, to your doctor.Diarrhoea, dizziness, tiredness, nervousness, tremor, concentration problems, emotional reactions, and speech impairment.
TIGABINE
ADVANTAGES: Minimal effect on other medications
DISADVANTAGE
.Dose is dependent on concurrent AEDs.
Anxiety.
Occasionally makes some seizure types Worse
LEVETIRACETAM
Binds to synaptic vesicle protein SV2A
which is involved in synaptic vesicle exocytosis
LEVITIRACETAM
Generic name: Levetiracetam
Available as: Desitrend: granules 250mg, 500mg, 1000mg.Keppra: tablets 250mg, 500mg, 750mg, 1000mg, oral solution 100mg/ml. Levetiracetam: tablets 250mg, 500mg, 750mg, 1000mg, oral solution 100mg/ml.
Average total daily dose: Up to 1500mg twice daily.
Doses per day: 2
Treatment: Monotherapy and add-on therapy for focal seizures with or without secondary generalisation. Add-on therapy for myoclonic seizures in Juvenile Myoclonic Epilepsy.
Most common possible side effects include the following:Anorexia, weight changes, abdominal pain, nausea, vomiting, diarrhoea, drowsiness, unsteadiness, dizziness, headache, tremor, amnesia, aggression, agitation, depression, anxiety, and double or blurred vision.
LEVETIRACETAM
ADVANTAGES: No interactions
Minimal liver metabolism
Works for most seizure types
Can start Quickly
Well tolerated
Liquid formulation
DISADVANTAGES: Behavioral/psych side effects
Twice per day
OXCARBAZEPINE
Oxcarbazepine is a prodrug which is activated to eslicarbazepine in the liver.
Same mechanism as carbamazepine – sodium channel inhibition and is generally used to treat the same conditions.
reduce the impact on the liver of metabolizing the drug, and also prevents the serious forms of anemia or agranulocytosis occasionally associated with carbamazepine
OXCARBAZEPINE
Generic name: Oxcarbazepine
Available as:tablets 150mg, 300mg, 600mg, oral suspension 60mg/ml.
Average total daily dose: Up to 18 years: 30mg/kg daily divided into 2 or 3 doses, up to 46mg/kg. From 18 years: 600mg – 2400mg daily divided into 2 or 3 doses.
Doses per day: 2 – 3
Treatment: Effective for focal seizures, tonic clonic seizures and secondarily generalised tonic clonic seizures.
Most common possible side effects include the following. Skin rash. Nausea, vomiting, constipation, diarrhoea, abdominal pain, dizziness, headache, drowsiness, agitation, amnesia, hair loss, weakness, unsteadiness, confusion, depression, and tremor.
OXCARBAZEPINE
ADVANTAGES:
As effective and better tolerated than Carbamazepine
Fewer interactions than Carbamazepine
Approved for children > 4
Approved for first-line monotherapy
DISADVANTAGES:
Not for all seizure types
Low sodium, esp if on diuretics also
Lessens effectiveness of birth control pill
ZONISAMIDE
Weak carbonic anhydrase inhibitory action
Prolongation of Na+ channel inactivation
resulting in suppression of repetitive neuronal
firing has been observed
ZONISAMIDE
Generic name: Zonisamide
Available as:capsules 25mg, 50mg, 100mg.
Average total daily dose: From 18 years: 300mg – 500mg daily divided into 1 or 2 doses.
Doses per day: 1 – 2
Treatment: Add-on therapy for focal seizures with or without secondary generalisation.
Most common possible side effects include the following:Skin rash. Nausea, diarrhoea, abdominal pain, constipation, indigestion, anorexia, weight loss, drowsiness, dizziness, confusion, agitation, irritability, depression, psychosis, and unsteadiness
ZONISAMIDE
ADVANTAGES: Used in Japan for many years
Works for all seizure types
Approved for children
Once daily
Weight loss
Recent addition of 25 mg capsules
DISADVANTAGES: 1-2% kidney stones
Occasional psychiatric or sedative side effects
PREGABALIN
Binds to the α2-δ protein subunit of
voltage-gated calcium channels
This closes N and P/Q presynaptic calcium channels,
diminishing excessive neuronal activity and
neurotransmitter release
PREGABALIN
Generic Name:Pregabalin
Available as:tablet
Average total daily dose: 150–600 mg/DAY
Doses: Start treatment with 50 mg/day in two divided doses
Treatment: Adjunctive treatment of partial seizures with or without secondary generalization in adults
Most common possible side effects include the following: Somnolence, dizziness,Ataxia, tremor, dysarthria, paresthesia,Impaired attention, euphoric mood, irritability, Vomiting, dry mouth, constipation
PREGABALIN
ADVANTAGES
Peripheral and central neuropathic pain
Generalized anxiety disorders
Management of pain associated with diabetic peripheral neuropathy
Management of postherpetic neuralgia
Management of fibromyalgia
DISADVANTAGES
Blurred vision, diplopia,Peripheral edema Rare- neutropenia,
hypoglycemia,
atrioventricular block
and congestive heart failure
LACOSAMIDE
Acts by enhancing slow inactivation of
voltage-gated sodium channels
resulting in stabilization of hyperexcitable
neuronal membranes
LACOSAMIDE
Generic name: Lacosamide
Available as: Tablets 50mg, 100mg, 150mg, 200mg, syrup 10mg/ml.
Average total daily dose: From 16 years: 200mg twice a day.
Doses per day: 2
Treatment: Add-on therapy for focal seizures with or without secondary generalisation.
Most common possible side effects include the following.Nausea, vomiting, constipation, wind, dizziness, headache, impaired coordination, drowsiness, tremor, depression, fatigue, abnormal walking, blurred vision, abnormal eye movements, and itching.
LACOSAMIDE
ADVANTAGES: Recently been licensed for clinical use.
Adjunctive treatment of partial onset seizure.
In patients with epilepsy aged 16 years & older.
DISADVANTAGES: Dizziness, headache, balance disorder, abnormal coordination
memory impairment, somnolence, tremor, nystagmus
Diplopia
Nausea, vomiting, constipation
Pruritus
Increases PR interval
ESLICARBAZEPINE ACETATE
Acts as a use-dependent blocker of
voltage-sensitive sodium channels
resulting in stabilization of hyperexcitable
neuronal membranes
ESLICARBAZEPINE ACETATE
Generic name: Eslicarbazepine acetate
Available as:tablets 800mg.
Average total daily dose: From 18 years: 800mg once a day, up to 1200mg.
Doses per day: 1
Treatment: Effective as an add-on therapy for focal seizures, tonic clonic and secondarily generalised tonic clonic seizures.
Most common possible side effects include the following.Skin rash. Nausea, vomiting, diarrhoea, dizziness, drowsiness, headache, impaired coordination, tremor, visual problems, and fatigue.
ESLICARBAZEPINE ACETATE
ADVANTAGES:
Adjunctive treatment of partial onset seizures with or without secondary generalization
in patients with epilepsy aged 16 years and older
. Oral bioavailability: >90%
Dosing schedule is once per day
Dose adjustment is not necessary in Hepatic impairment
DISADVANTAGES:
Increases PR interval
Increased risk of suicidal ideation
Stevens-Johnson syndrome
Severe renal impairment (CrCL <30 mL/min) results in a 90% decrease in clearance so is not recommended for these patients
RUFINAMIDE
While the exact mechanism of rufinamide is still unknown, it is thought to act through modulation of sodium channels resulting in membrane stabilization.
Rufinamide administration slows recovery after a prolonged prepulse in cortical neurons and limits sustained repetitive firing of sodium-dependent action potentials.
RUFINAMIDE
Generic name: Rufinamide
Available as):tablets 100mg, 200mg, 400mg, oral suspension 40mg/ml.
Average total daily dose: 900mg – 1600mg (depending on body weight and whether also taking sodium valproate) twice daily.
Doses per day: 2
Treatment: Add-on therapy for Lennox-Gastaut syndrome
Most common possible side effects include the following.Hypersensitivity syndrome (possibly including rash and fever) – if concerned seek immediate medical attention. Nausea, vomiting, diarrhoea, constipation, indigestion, abdominal pain, weight loss, anorexia, runny nose, nosebleeds, dizziness, headache, drowsiness, insomnia, anxiety, tiredness, flu-like symptoms, and blurred or double vision.
RETIGABINE
Opens KCNQ2/3 (Kv7.2/7.3) voltage-gated potassium channels on neurons and activates M-current, which regulates neuronal excitability and suppresses epileptic activity.
RETIGABINE
Generic name: Retigabine
Available as:tablets 50mg, 100mg, 200mg, 300mg, 400mg.
Retigabine is not widely prescribed due to possible side effects.
Average total daily dose: From 18 years: 600mg – 1200mg daily divided into 3 doses.
Doses per day: 3
Treatment: Add-on therapy for focal seizures with or without secondary generalisation.
Most common possible side effects include the following.skin rashDizziness, sleepiness, fatigue, weight gain, confusion, anxiety, tremor, double or blurred vision, nausea, constipation, and problems urinating. Retigabine can cause problems with heart rhythm
INTRANASAL OR BUCCAL MIDAZOLAM
Safe and effective (studies in UK, Israel): 5-10 mg in adults
Easy to use
Less social stigma
Not approved in US for this usage
Not easy to obtain (controlled substance) in a convenient form
Shorter acting than Diastat
CONSIDERATIONS IN CHOOSING AN AED
Side effect profile
Efficacy and correct seizure/syndrome diagnosis
Convenience (doses/day, etc) Once/day
Cost
Drug interactions/potential for future problems
Non-epileptic indications for AEDs Pain Headaches Psychiatric
Concurrent medical problems
DRUGS THAT DECREASE EFFICACY OF ORAL CONTRACEPTIVES
Phenytoin
Carbamazepine
Phenobarbital
Primidone
Topiramate at higher doses
Oxcarbazepine
WEIGHT ISSUES
Risk of weight gain Valproate Gabapentin and Pregabalin
“Risk” of weight loss Topiramate Zonisamide Felbamate
LIFESTYLE CHANGES TO MINIMIZE SEIZURES
Avoid sleep deprivation
Avoid alcohol
Treat fevers quickly
Occasional patients should avoid specific factors such as strobe lights, etc
Pill boxes/reminders
SPECIAL CASES
Contraception:
Lamotrigine and oxcarbazepine have little interaction, and sodium valproate has no interaction with oral contraception.
Pregnancy :
Epilepsy presents specific management problems during pregnancy. With the exception of gabapentin, treatment with almost all anticonvulsant drugs is associated with an increased incidence of fetal congenital abnormalities such as cleft lip, spina bifida and cardiac defects
GUIDELINES FOR ANTICONVULSANT THERAPY
Start with one first-line drug
Start at a low dose; gradually increase dose until effective control of seizures is achieved or side-effects develop (drug levels may be helpful)
Optimise compliance (use minimum number of doses per day)
If first drug fails (seizures continue or side-effects develop), start second first-line drug whilst gradually withdrawing first
If second drug fails (seizures continue or side-effects develop), start second-line drug in combination with preferred first-line drug at maximum tolerated dose (beware interactions)
If this combination fails (seizures continue or side-effects develop), replace second-line drug with alternative second-line drug
If this combination fails, check compliance and reconsider diagnosis (is there an occult structural or metabolic lesion or are seizures truly epileptic?)
If this combination fails, consider alternative, non-drug treatments (e.g. epilepsy surgery, vagal nerve stimulation)
Do not use more than two drugs in combination at any one time
CONCLUSION
The guideline is intended to act as a working model for managing patients with epilepsy. Every medical practitioner needs to combine guidelines with his/her own skill, knowledge and experience keeping in mind the needs of individual patients. With so many new AEDs in the market, a physician might be tempted in trying them out but the first-line AEDs still remain the most preferred agents in India considering their wide availability, known long-term toxicity profile, wide experience with these agents and cheap price. Since a patient has to take these drugs for a long time and ensuring drug compliance is a key issue, appropriate choice of the drug is important.
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