Antiepileptic drugs PDF

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Antiepileptic drugs...

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Antiepileptic drugs Epilepsy: chronic pattern of seizures, excessive electrical activity of neurons. ECG is used to diagnose it Seizure: brief episode of abnormal electrical activity in nerve cells of the brain, it may or not lead to convulsion. Low levels of GABA are associated with seizures Convulsion: involuntary spasmodic contractions of any or all voluntary muscles throughout the body, Status epilepticus: Multiple seizures occur with no recovery between them. Is a true medical emergency • Result: – Hypotension – Hypoxia – Brain damage – Death Antiepileptic Drugs (AEDs) - Also called anticonvulsants - Goals of therapy o To control or prevent seizures while maintaining a reasonable quality of life o To minimize adverse effects and drug-induced toxicity - AED therapy is usually lifelong - Combination of drugs may be used - Single-drug therapy started before multiple-drug therapy is tried - Second and third generation of antiepileptic drugs tend to have fewer adverse effects, so this may benefit older adults If pt has a low serum level, this means that he is not taking the med as prescribed If the pt has serum level is above normal, contact the prescriber before the next dose

Antiepileptic drugs traditionally used to manage seizure disorders include: – Barbiturates – Hydantoins – Iminostilbenes plus valproic acid – Second- and third generation antiepileptics Mechanism of Action and Drug Effects - The exact mechanism of action is unknown, but there is evidence that they alter the movement of Na, K, Ca and Mg ions. The changes result in a more stable and less excitable membrane •

Pharmacologic effects: – Reduce nerve’s ability to be stimulated – Suppress transmission of impulses from one nerve to the next – Decrease speed of nerve impulse conduction within a neuron

Indications • Prevention or control of seizure activity • Long-term maintenance therapy for chronic, recurring seizures • Acute treatment of convulsions and status epilepticus (Diazepam and Lorazepam) Adverse Effects • Adverse effects often necessitate a change in medication • GI side effects includes N/V and diarrhea • Black box warning as of 2008 • Suicidal thoughts and behavior Monitor pt for depression, suicidal thoughts, changes in behavior • Long-term therapy with phenytoin may cause gingival hyperplasia, acne, hirsutism, and Dilantin facies Interactions • Many antiepileptic drugs interact with each other • Induce hepatic metabolism resulting in reduction of effects of other drugs • Interfere with birth control • Avoid grapefruit with carbamazepine Barbiturates Phenobarbital and Primidone—most common used drugs

Primidone is metabolized in the liver to phenobarbital Most common adverse effect: sedation Therapeutic effects: serum levels of 10-40 µg/mL. Taken once a day bc its long half-life • Contraindications: known allergy, porphyria, liver or kidney impairment, and respiratory illness Hydantoins Phenytoin  First line drug used, is a prototypical drug  Adverse effects: gingival hyperplasia, acne, hirsutism, Dilantin facies, and osteoporosis.  The most common adverse effects are lethargy, abnormal movements, mental confusion and cognitive changes  Therapeutic levels are usually 10-20 µg/mL  Highly protein bound  If a skin rash is developed in a child taking phenytoin, discontinue the med and contact the HCP  Intravenous (IV) administration o Very irritating to veins o Slow IV directly into a large vein through a large-gauge (20gauge or larger) venous catheter o Diluted in normal saline (NS) for IV infusion o Filter must be used o Saline flush Fosphenytoin is an injectable watersoluble prodrug of phenytoin that can be given IM or IV without causing burning on injection associated with phenytoin • • •

Iminostilbenes Carbamazepine • Second most prescribed antiepileptic in US after phenytoin. Do not take grapefruit juice

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Autoinduction of hepatic enzymes – Autoinduction is a process in which, over time, a drug stimulates the production of enzymes that enhance its own metabolism, which leads to lower than expected drug concentrations – Interacts with NSAIDs

Oxcarbazepine – chemical analogue of carbamazepine; for partial seizures – Adverse reactions: headache, dizziness, nausea Nursing Implications • Assessment – Health history, including current medications – Drug allergies – Liver function studies, CBC – Baseline vital signs • Oral drugs – Take regularly, same time each day – Oral forms of valproic acid, do not take them with meals or carbonated beverages – Take with meals to reduce GI upset – Do not crush, chew, or open extended-release forms – Chewable dosages are not recommended for once-a-day administration – If patient is NPO for a procedure, contact prescriber regarding AED dosage • Intravenous forms – Follow manufacturer’s recommendations for IV delivery—usually given slowly – Avoid extravasation of fluids – Use only normal saline with IV phenytoin (Dilantin) – IM injections of barbiturates or phenytoin must never be used • Teach patients that therapy is long term and possibly lifelong (not a cure) • Monitor for therapeutic effects – Decreased or absent seizure activity • Monitor for adverse effects – Mental status changes, mood changes, changes in level of consciousness or sensorium – Eye problems, visual disorders

– Sore throat, fever (blood dyscrasias may occur with Dilantin) -

Before administering any med, review RBC, WBC, BUN, clotting, renal or liver function studies If using Barbiturates, assess the neurologic system and vital signs bc of the CNS depression associated with it With hydantoins like phenytoin perform a skin assessment and document the presence or absence of any rash, perform a baseline dental hygiene habits and an oral assessment bc of the adverse effects of gingival hyperplasia. Also do a baseline liver function studies and a CBC

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Most common adverse effects are drowsiness, GI upset and CNS depression

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Drug interactions occurs with beta blockers, corticosteroids, CCB and alcohol...