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52 Cards in this Set

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Are bentobarbital and secobarbital ultrashort-, intermediate-, or long-acting?
Intermediate
Where do barbituates act?
They may act at Ci- ionophore of GABA receptor, facilitating GABAergic transmission
What do barbituates cause?
Widespread CNS depression ranging, with increasing dose, from mild sedation through drowsiness, anesthesia, coma, and death (due to profound depression of respiratory and vasomotor centers in medulla)
What terminates the action of ultra-short acting barbituates?
Action terminated by redistribution and metabolism
Desribe short-acting barbituate metabolism
Mainly hepatic metabolism
Desribe intermediate-acting barbituate metabolism
Mainly hepatic metabolism
Describe long-acting barbituate metabolism
Hepatic metabolism and renal excretion of unmetabolized drug.
What are the untoward effects of barbituates?
1. Daytime Hangover
2. Cross-tolerance
3. Taken concurrently with other depressants, such as ethanol, can cause severe CNS depression
4. Respiratory depression
5. Paradoxical excitement, especially in children and the elderly
6. Therapeutic index decreases with sustained use
What non-clinical use are barbituates frequently used for?
Suicide attempts
What are the signs of barbituate intoxication?
a. Moderate intoxication resembling inebriation
b. Depression of medulla results in respiratory depression and hypotension.
c. Death can result from respiratory or renal failure
What is the supportive treatment for barbituate poisoning?
Dialysis
What are the clinical uses of barbituates?
1. Ultrashort used as IV anesthetics
2. Phenobarbital for seizures
What is epilepsy?
A chronic CNS disorder involving sudden, transitory change in sensory and/or motor functioning (seizure).
What occurs on hte cellular level during a seizure?
Synchronous repetitive firing of brain cells, either locally (focal) or globally
What can cause a seizure in a patient?
May have no identifiable cause (primary/idiopathic) or may be caused by variety of insults to brain (secondary/symptomatic), such as tremors, inflammation, head injuries.
What are the causes of seizures on a cellular level?
Possible causes:
a. Change in balance of excitatory and inhibitory inputs; reduction in GABA-mediated feed-forward excitation, perhaps mediated by NMDA receptors.
b. Change in membrane properties of dendrites; ionic conductances contribute to tendency for bursting
What are the characteristics of a simple partial seizure?
Motor (clonic twitching) or sensory (tingling) abnormalities in one area of the body; spreading to adjacent areas; no impairment of consciousness.
What are the therapeutic agents for a simple partial seizure?
Phenytoin*
Carbamazepine*
Phenobarbital
Valproic acid
Primidone
Gabapentin
Lamotrigine
Topiramate
What are the characteristics of a complex partial seizure?
Confusion, impairment of consciousness, stereotyped repeated movements, e.g. chewing
What are the therapeutic agents for a complex partial seizure?
Phenytoin*
Carbamazepine*
Phenobarbital
Valproic acid
Primidone
Gabapentin
Tiagabine
What are the characteristics of a generalized absence (petit mal) seizure?
Brief loss of consciousness, often with local or widespread clonic movements
What are the therapeutic agents for an absence (petit mal) seizure?
Ethosuximide*
Valproic acid*
Clonazepam
What are the characteristics of a generalized tonic-clonic (grand mal) seizure?
Loss of consciousnes, tonic spasm of entire body, then synchronous clonic movements; followed by confusion, sleep
What are the therapeutic agents for a generalized tonic-clonic (grand mal) seizure?
Phenytoin*
Carbamazepine*
Valproic acid*
Phenobarbital
Primidone
Lamotrigine
Topiramate
What are the characteristics of generalized status epilepticus?
Series of tonic-clonic seizures so closely spaced that consciousness is not regained between seizures
What are the therapeutic agents for generalized status epilepticus?
Diazepam*
Lorazepam*
Phenytoin*
Phenobarbitol*
What are the uses of phenobarbital?
i. Tonic-clonic and cortical focal, often concurrently with phenytoin, status epilepticus (IV).
ii. Agent of first choice for young children (less than 5 years)
What is the cellular mechanism of action for phenobarbital?
Possibly be reducing high-frequency firing and enhancing GABAergic inhibition
Describe the uptake of phenobarbital
i. Absorbed well from gut
ii. Half bound to plasma proteins
Describe elimination of phenobarbital
i. Up to 25% by renal excretion, remainder by hepatic (enzymatic) inactivation.
ii. Induces hepatic microsomal enzymes.
iii. Concurrently administered valproate causes phenobarbital plasma concentration to rise.
iv. t1/2 ~ 90 hrs
What are the side effects of phenobarbital?
Sedation
Fatigue
Tolerance to these as well as anticonvulsants effects may develop
What are the uses of phenytoin?
i. Primary agent in treatment of tonic-clonic, cortical focal and psychomotor seizures, especially for patients over the age of 5.
ii. Preferred for psychomotor seizures, especially if there are associated tonic-clonic seizures.
iii. Status epilepticus (IV)
What is the cellular mechanism of action for phenytoin?
Reduces high-frequency firing by increasing Na+ inactivation
Explain the uptake of phenytoin
i. Absorbed slowly from the guy
ii. 90% in plasma bound to protein, mainly albumin
Explain the elimination of phenytoin
i. Almost all phenytoin inactivated by hepatic enzymes.
ii. Dose-dependent elimination:
- first order at low to moderate plasma concentrations, zero order at higher concentrations.
- at higher concentrations, t1/2 increases as concentration increases, so on regular dosing regimen, plateau plasma concentration increases more than would be expected as dose increases.
iii. Elimination also affected by several drugs when administered concurrently.
What are the side effects of phenytoin?
Sedation (much less than phenobarbital)
Ataxia
Nystagmus
Nausea
Gingival hyperplasia (especially in children)
Hirsutism
Describe the structure of carbamazepine
Unrelated to barbiturates, related to tricyclic antidepressants
What is the cellular mechanism of action for carbamazepine?
Possibly by reducing high-frequency firing by increasing sodium inactivation.
What are the uses of carbamazepine?
i. For psychomotor, tonic-clonic and cortical focal seizures.
ii. Often preferred over phenytoin for children and young women because it does not cause gingival hyperplasia or hirsutism.
What are the side effects of carbamazepine?
i. Sedation, vertigo, etc.
ii. Possibility of serious liver and bone marrow problems
Describe tiagabine
i. Inhibits neuronal and glial uptake of GABA
ii. Partial seizures, especially complex
Describe gabapentin and pregabalin
i. They are GABA analogs, but the mechanism of action is uncertain
ii. Partial seizures
Describe lamotrigine
It is for partial and tonic-clonic seizures
Describe topiramate
i. Inhibitor of carbonic anhydrase - this may affect GABAergic transmission.
ii. Partial and tonic-clonic seizures
Describe the use of new drugs
New drugs currently used mainly as add-ons
Describe the uses, cellular mechanism of action, uptake, elimination, and side effects of Ethosuximide
a. Uses
Preferred agent for absences.
b. Cellular mechanism of action
Reduces slow frequency, pacemaker-driven repetitive firing by blocking Ca++ T channels.
c. Uptake
From gut.
d. Elimination
Most metabolized in liver to inactive compound.
e. Side effects
Nausea, lethargy, ataxia; serious side effects unlikely.
Describe the uses, uptake, elimination and side effects of Valproate
a. Uses
i. Absences
ii. Tonic-clonic
iii. Cortical focal
b. Uptake
Rapid from the gut.
c. Elimination
i. Short t.
1/2ii. Most metabolized by liver.
d. Side effects
Less likely than with other drugs.
What are the benzodiazepines?
Clonazepam
Diazepam
Lorazepam
Describe clonazepam
Benzodiazepine
i. Used to suppress absence seizures
ii. Substantial tolerance to anti-seizure activity often develops; also can cause hyperactivity and restlessness in children, so is not an agent of choice.
Describe diazepam and lorzepam
Benzodiazepines
i. Used for status epilepticus
ii. Administered intravenously
What are the principles of treatment with barbituates and and anti-epileptic drugs?
1. Start and stop treatment gradually
2. Monitor plasma concentration of drug when starting treatment
3. Use multi-drug therapy only when monotherapy is clearly insufficient
Describe the use of anti-epileptic drugs (AEDs) for conditions other than epilepsy
1. many prescriptions of AEDs are not for epilepsy
2. Most common uses are for neuropathic pain (phenytoin, carbamazepine, gabapentin, pregabalin) and migraine (valproate); may be some commonality in etiologies of these and seizures
3. Also used to treat numerous movement disorders (e.g. essential tremor) and trigeminal neuralgia (carbamazepine).
4. AEDs also effective for psychiatric disorders (e.g. bipolar disorder and schizophrenia), though reasons for effectiveness unclear