Anticonvulsants Part 2 (Drugs) Flashcards
(43 cards)
Mechanism of action for carbamazepine (Tegretol)
Blocking sodium channels in neurons which blocks propagation of impulses
- inhibition of high-frequency repetitive firing in neurons
- decrease in synaptic transmission (presynaptically)
Tegretol is highly effective for what seizures?
simple and complex partial seizures
Other clinical uses for Tegretol
- Management of bipolar depression
- Management of chronic pain
DENTISTRY: Treatment of trigeminal neuralgia
Adverse drug reactions for Tegretol
- CNS effects
- GI adverse effects
- Hematologic: causes aplastic anemia (wipes out bone marrow)
- Dermatologic: rashes, photosensivity, etc.
- Has potential for inducing serious liver toxicity
- Congestive heart failure, altered blood pressure
- XEROSTOMIA
Drug interactions of Tegretol
“Classic Inducer”
- Decreases effectiveness of warfarin (Coumadin), doxycycline, theophylline (bronchodilator for asthma), oral contraceptives
- erythromycin-type antibiotics (macrolides) increase carbamazepine blood levels (toxicity)
- carbamazepine may increase hepatotoxicity of acetaminophen (Tylenol)
Mechanism of action for phenytoin (Dilantin)
Stabilizes neuronal membranes by decreasing the neuronal membrane passage of sodium ions
- reduces Na influx and Ca passage through membranes
- Interferes with calcium mediated release of neurotransmitters
- Reduces propagation of abnormal impulses in the brain to reduce the frequency of seizures
Dilantin is highly effective for what kind of seizures
- all partial seizures (both simple and complex partial)
- tonic-clonic seizures
- status epilepticus
what is Dilantin not effective against?
Absence seizures (petit mal)
Dental use of Dilantin
trigeminal neuralgia
Adverse effects of Dilantin
Nausea, vomiting
Loss of taste
Megaloblastic anemia - interferes with B12 metabolism
CNS - confusion, drowsiness, dizziness
Dermatologic: rash, hirsuitism
Vitamin D and folate deficiencies = osteoporosis;
- **FIRST symptom of folate deficiency may be oral mucosal ulceration or glossitis
- *Gyngival hyperplasia - overgrowth of connective tissue
Describe more in depth the adverse effect of gingival hyperplasia that Dilantin can have
50-60% of patients taking phenytoin experience GH
- Increased in presence of inflammation
- **Good oral hygiene reduces extent/severity
- Slowly regresses after termination of drug therapy
- May require surgical excision if severe (gingivectomy)
Describe the teratogenic effect of Dilantin
FDA category D
- Fetal syndrome includes cleft lip, cleft palate, congenital heart disease
Describe the drug interactions of Dilantin
Many drug interactions
- phenytoin (Dilantin) causes increases in the metabolism of many drugs
- Cytochrome P450 “Inducer”
Explain the action of GABAmimetic Agents
cause release of GABA from presynaptic interneurons
- encourage GABA fusion with presynaptic neuron
- **Inhibits the release of acetylcholine from the presynaptic neuron
- Many seizures are caused by tremendous release of acetylcholine across synapses in cortex
- GABA = inhibitory neurotransmitter (presynaptically)
Mechanism of action for phenobarbital (Luminal)
reduces Na and K transport along axonal membranes; potentiates the inhibitory effects of GABA-mediated neurons (GABAmimetic)
What is the GENERAL action of Luminal
General depressant to CNS
- Limits the spread of seizure discharge in the brain
What is the most common barbiturate used as an anticonvulsant?
phenobarbital (Luminal sodium)
phenobarbital (Luminal sodium) is indicated for what seizure types?
tonic-clonic
partial seizure types (both)
Most common side effect of phenobarbital (Luminal sodium)
Sedation
- Rarely = skin reactions;**Stomatitis may indicate onset of cutaneous reactions, some of which have been fatal
Describe the drug interactions of phenobarbital (Luminal sodium)
Strong “inducer”
- oral contraceptives, mycins, warfarin
- Enhances the hepatotoxicity of acetaminophen
- Additive CNS effects = all CNS depressants, narcotics, alcohol, antidepressants, BDZs = increased risk for respiratory depression
Which other anticonvulsant is chemically related to phenobarbital?
primidone (Mysoline)
- primidone metabolized in liver to phenobarbital (precursor to phenobarbital)
- Much of its actions come from phenobarbital
primidone (Mysoline) is used to treat what type of seizures?
Partial seizures and tonic-clonic seizures
Mechanism of action for valproates?
causes increased availability of GABA to neurons
- enhances action of or mimics the effects of GABA presynaptically
Valproic acid (Depakene) is used for:
Tonic-clonic seizures
Generalized seizures
- Absence (petit mal)
- Myoclonic
