Neuro drugs Flashcards
What classes of drugs can be used to treat glaucoma?
alpha-agonists, beta-blockers, diuretics, cholinomimetics, prostaglandin
Alpha-agonists for glaucoma
Epinephrine (alpha1), Brimonidine (alpha2)
Mechanism: both decrease aqueous humor synthesis (epinephrine via vasoconstriction)
Side effects: mydriasis (epinephrine) blurry vision, ocular hyperemia, foreign body sensation, allergic rxn, ocular pruritis
When is epinephrine contraindicated for use in glaucoma?
Do NOT use with closed-angle glaucoma! Will make it worse
Beta-blockers for glaucoma
Timolol, betaxolol, carteolol
mechanism: decrease aqueous humor synthesis
diuretics for glaucoma
Acetazolamide
Mechanism: decrease aqueous humor synthesis via inhibition of carbonic anhydrase
cholinomimetics for glaucoma
Direct: pilocarpine, carbachol
Indirect: physostigmine, echothiophate
Mechanism: increase outflow of aqueous humor via ciliary muscle contraction and opening trabecular meswork
side effects: miosis and cyclospams (contraction of ciliary muscle)
What is the best drug to use in glaucoma emergency?
Pilocarpine - very effective at opening meshwork into canal of Schlemm
Prostaglandin for glaucoma
Latanoprost (PGF2alpha)
Mechanism: increase outflow of aqueous humor
Side effects: darkening of iris
What is the mechanism of opioid analgesics?
Agonists at opioid receptors (mu=morphine, delta= enkephalin, kappa= dynorphin) -> open K+ channels and close Ca2+ channels -> decrease synaptic transmission
Inhibit release of ACh, NE, 5-HT, glutamate, substance P
What are examples of opioid analgesics and what is their clinical use?
morphine, codeine, fentanyl, meperidine, pentazocine
Pain, cough suppression - dextromethorphan
diarrhea - loperamide, diphenoxylate
acute PE
maintenance for heroin addicts (methadone, buprenorphine + naloxone)
What are the toxicities of opioid analgesics?
addiction, respiratory depression, constipation, miosis, additive CNS depression. Do NOT develop tolerance to miosis and constipation. Toxicity treated with naloxone or naltrexone (opioid antagonist)
Butorphanol
mechanism: kappa-opioid receptor agonist and mu-opioid receptor partial antagonist
Use: severe pain (migraine, labor); causes less respiratory depression than full opioid agonists
Toxicity: can cause opioid withdrawal symptoms if patient also taking full opioid agonist (acts as competition), overdose not easily reversed with naloxone
Tramadol
Mechanism: very weak opioid agonist; also inhibits 5-HT and NE reuptake
Use: chronic pain
Toxicity: similar to opioids, decreases seizure threshold, serotonin syndrome
What is first line for simple partial seizures?
Carbamazepine
What is first line for complex partial seizures?
Carbamazepine
What is first line for tonic-clonic seizures?
Phenytoin, carbamazepine or valproic acid
What is first line for absence seizures?
Ethosuximide
What is first line for status epilepticus? What is used for prophylaxis for status epilepticus
acute: Benzodiazepines (diazepam, lorazepam)
prophylaxis: Phenytoin
Ethosuximide
Uses: 1st line for absence seizures
Mechanism: blocks thalamic T-type Ca2+ channels
Side effects: GI, fatigue, HA, urticaria, Stevens-Johnson syndrome
Notes: “Sux to have Silent Seizures”
Benzodiazepines
Diazepam, lorazepam, triazolam, temazepam, oxazepam, midazolam, chlordiazepoxide, alprazolam
Uses: Anxiety, spasticity, acute status epilepticus (diazepam, lorazepam), detoxification (especially alcohol - DTs), night terrors, sleep walking, general anesthesia
Mechanism: increases action of GABA-A by increasing FREQUENCY of Cl- channel opening. Decreases REM sleep.
(Note: alprazolam, triazolam, oxazepam and midazolam are short acting -> higher addiction potential)
Side effects: Sedation, tolerance, dependence, respiratory depression (less risk of respiratory depression than barbituates) *Treat overdose with flumazenil (competitive antagonist)
Notes: Also used for eclampsia seizures, but 1st line is MgSO4
Phenytoin
Uses: 1st line for tonic-clonic seizures, prophylaxis for status epilepticus, also used for partial seizures
Mechanism: increase Na+ channel inactivation, 0-order kinetics!!
Side effects: nystagmus, diplopia, ataxia, gingival hyperplasia, hirsutism, peripheral neuropathy, megaloblastic anemia, TERATOGEN, SLE-like syndrome, induces P450, LAD, Stevens-Johnson, osteopenia
Notes: Fosphenytoin for IV
Carbamazepine
Uses: a first line drug for partial seizures and tonic-clonic seizures
Mechanism: increases Na+ channel inactivation
Side effects: Diplopia, ataxia, blood dyscrasias (agranulocytosis, aplastic anemia), hepatotoxicity, induction of P450, SIADH, Steven-Johnson syndrome, CONTRAINDICATED IN PREGNANCY- teratogenesis,
Notes: 1st line for trigeminal neuralgia
Valproic acid
Uses: one of the 1st line drugs for tonic-clonic seizures, also used for partial seizures and absence seizures
Mechanism: increases Na+ channel inactivation, increases GABA by inhibiting GABA transaminase
Side effects: GI distress, rare but fatal hepatotoxicity (measure LFTs), tremor, weight gain, CONTRAINDICATED IN PREGNANCY - neural tube defects
Notes: also used for myoclonic seizures, bipolar disorder
Gabapentin
Uses: simple and complex partial seizures
Mechanism: inhibits high-voltage-activated Ca2+ channels; GABA analog
Side effects: sedation, ataxia
Notes: also used for peripheral neuropathy, postherpetic neuralgia
Phenobarbital
Uses: simple and complex partial seizures and tonic-clonic seizures
Mechanism: increases GABA-A action
Side effects: sedation, tolerance, dependence, induces P450, cardiorespiratory depression
Notes: 1st line in neonates*
Topiramate
Uses: simple and complex partial seizures and tonic-clonic seizures
Mechanism: Blocks Na+ channels, increases GABA action
Side effects: sedation, mental dulling, kidney stones, weight loss
Notes: also used for migraine prevention
Lamotrigine
Uses: All seizures, except status epilepticus
Mechanism: Blocks voltage-gaited Na+ channels
Side effects: Sevens-Johnson syndrome
Notes: must titrate slowly!
Levetiracetam
Uses: simple and complex partial seizures and tonic-clonic seizures
Mechanism: unknown, may modulate GABA, glutamate release
Tiagabine
Uses: simple and complex partial seizures
Mechanism: increase GABA by inhibiting reuptake
Vigabatrin
Uses: simple and complex partial seizures
Mechanism: increase GABA by inhibiting GABA transaminase
Barbituates
(-barbital/-pental) phenobarbital, pentobarbital, thiopental, secobarbital
Mechanism: increases DURATION of Cl- channel opening -> decreases neuron firing Note: contraindicated in porphyria
Clinical use: sedative for anxiety, seizures, insomnia, anesthesia (thiopental)
Toxicity: cardiorespiratory depression, CNS depression (exacerbated by EtOH use), dependence, induces P450
Overdose treatment is supportive
Nonbenzodiazepine hypnotics
Zolpidem, zaleplon, eszopiclone
Mechanism: act via BZ1 subtype of GABA receptor. Reversed by flumazenil
Uses: insomnia “All ZZZs put you to sleep”
Toxicity: ataxia, HA, confusion. Short acting due to rapid liver metabolism. Modest day-after psychomotor depression and few amnestic effects, lower dependence risk than benzos
What is the MAC?
Minimal alveolar concentration of inhaled anesthetic required to prevent 50% of patients from moving in response to noxious stimuli
potency is proportional to 1/MAC –> potency increases with lower MAC
What are examples of inhaled anesthetics, what are there effects and toxicity?
Halothane, enflurane, isoflurane, sevoflurane, methoxyflurane, N2O
Effects: myocardial and respiratory depression, nausea/emesis, increase cerebral blood flow (decrease cerebral metabolic demand)
Toxicity: Hepatotoxicity (halothane), nephrotoxicity (methoxyflurane), proconvulsant (enflurane), expansion of trapped gas (N2O)
What drugs can cause malignant hyperthermia and what is the treatment?
Inhaled anesthetics (except N2O) and succinylcholine induce fever and severe muscle contractions. Treat with dantrolene
What barbituate is used for IV anesthesia?
Thiopental - high potency and high lipid solubility, rapid brain entry
Used for induction of anesthesia and short procedures
Effects terminated by rapid redistribution. Decreases cerebral blood flow
Which benzo is commonly used for IV anesthesia
Midazolam most common for endoscopy, used with gas anesthetics and narcotics. May cause anterograde amnesia and severe post-op respiratory depression -> give flumazenil for OD
How are arylcylcohexylamines (ketamine) used for IV anesthesia?
PCP analogs act as dissociative anesthetics
Block NMDA receptors. Cardiovascular stimulants. Cause disorientation, hallucination, bad dreams. Increases cerebral blood flow