Neuro Pharm Flashcards
Lithium
Mechanism (not established)
Clinical use
Adverse effects
Mechanism: Not established; possibly related to inhibition of
phosphoinositol cascade.
Uses: Mood stabilizer for bipolar disorder;
blocks
relapse and acute manic events.
Adverse effects Tremor, hypothyroidism, polyuria (causes
nephrogenic diabetes insipidus), teratogenesis.
Causes Ebstein anomaly in newborn if taken by pregnant mother.
Narrow therapeutic
window requires close monitoring of serum
levels. Almost exclusively excreted by
kidneys; most is reabsorbed at PCT with Na+.
Thiazides (and other nephrotoxic agents) are implicated in lithium toxicity.
PCP
“hallucinogen”
- dissociative anesthetic
- long half life: 24 hours
- taken orally, IV, smoking, snorted
- PCP intoxication: psychosis resembling schizophrenia (paranoid, agitated, hallucinating)
- marked neurological signs: vertical nystagmus, ataxia
- profound autonomic effects (rapidly changing blood pressure, pulse)
- NMDA receptor/glutamate (which people found was linked to schizophrenia so it helped understand it.
Riluzole
Drug that can slow down progression of ALS by several months. It does this by blocking glutamate which is implicated in neurodegenerative diseases like ALS, Alzheimers, Parkinsons
Name the major types of autonomic receptors and where they are located
M1: CNS neurons, sympathetic postganglionic neurons, some presynaptic sites
*M2: myocardium, smooth muscle, some presynaptic sites
M3: exocrine glands, smooth muscle, vessels
*M4: expressed in CNS, forebrain, striatum, cortex, hippocampus
M5: predominant muscarinic receptor in neurons in VTA and substantia nigra
- opens K+ channels directly (beta subunit)
- rest works through increased IP3 and DAG, with increased intracellular calcium (alpha subunit)
List therapeutic uses for cholinesterase inhibitors
Short acting:
edrophonium • binds weakly and reversibly to anionic domain of AChE • rapid renal clearance, brief duration of action
*• used to diagnose myasthenia gravis (MG)
Intermediate acting inhibitors -
- rivastigmine for treating Alzheimer’s disease
- neostigmine, pyridostigmine, ambenonium, treat MG
- demecarium, physostigmine (physo cross BBB but is used topically)- treats glaucoma
Long-acting inhibitors of acetylcholinesterase: Covalent, not readily reversible
• organophosphate
insecticides
• chemical warfare agents
Recognize the major signs and symptoms of cholinergic excess with treatment
. Muscarinic: CNS stimulation • miosis (pupil constriction) • reflex tachycardia • bronchoconstriction (fight or flight you want to breath more) • excessive GI and GU smooth muscle activity • increased secretory activity (sweat, airway, GI and lacrimal glands) • vasodilation (sympathetic causes vasodilation of arteries carrying blood to muscles but at same time cause vasoconstriction of arteries carrying blood to unnecessary organs
Nicotinic • CNS stimulation (convulsions) followed by depression • neuromuscular end plate depolarization (fasciculations, then paralysis)
Treatment • if insecticide exposure, decontaminate to
prevent further absorption • maintain respiration, vital signs • administer atropine (muscarinic antagonist) • benzodiazepines for seizures
Cholinesterase inhibitor poisonning DUMBBELSS
Diarrhea Urination Miosis Bronchospasm Bradycardia Excitation (of skeletal muscle and CNS)* Lacrimation Sweating Salivation
Understand the mechanism of action of LA’s
Be able to describe the basic chemical structure of LA’s
Understand the effects of pH on the action of LA’s
Drug that reversibly blocks impulse
conduction along nerve axons and other
excitable membranes that utilize voltage gated sodium channels as the primary means of action potential generation.
Block Na+ channels in excitable
membranes without changing resting potential.
Reduce aggregate inward sodium
current
-Fibers that fire at a faster rate are more susceptible to the effects of local
anesthetics
Repeated depolarizations produce more effective anesthetic binding
This phenomenon is known as Frequency Dependent Block
Local anesthetics are weak bases
Therefore, the more acidic the pH, the
greater ionized, the more basic, the more neutral [B] form
The neutral form is required to get to site of action but charged form is required for activity.
Cocaine
- stimulant, vasoconstrictor
- used in ENT surgeries because it is a LA and also blocks nasal leakage
Tetracaine
A long duration, potent ester primarily used for spinal anesthesia, toxic at relatively low doses
(***exception to short acting ester rule)
-experienced a shortage and basically never made it back to market
Chloroprocaine
Used to have a bad rep, now a commonly used quick onset, short duration LA
-primarily used now for pregnancies, used for the last part of labor
Lidocaine
- the perfect local anesthetic
- non-irritating
- transient effect
- low systemic toxicity
- quick onset
- action to span duration of surgery
does have TNS implication
Mepivacaine
Longer duration than lidocaine
- *lowest pKa of injectable LA’s so it has one of the quickest onset
- acts as a vasoconstrictor
Prilocaine
Prilocaine: **known associated with methemoglobinemia
-component of EMLA
Bupivacaine
Excellent long duration LA with devastating potential for cardiac toxicity.
Sensory block>Motor block - great for pregnancies
Ropivacaine
Single enantiomer long duration
LA with properties similar to bupivacaine but
with less cardiotoxicity; vasoconstrictor
Understand the concepts of lipophilicity, pKa, and protein binding as they relate to potency, onset of action, and duration of LA’s
The greater the lipophilicity, the greater the potency and duration. However there is also slower onset of action. Often there is a lipid depot surrounding the nerve so there is greater diffusion.
A greater pKa of drug means slower onset of action because it will be more ionized and have difficulty entering cells.
Increased protein binding means increased duration of action
Understand the adverse effects of LA’s
SLAM
Systemic toxicity
Local toxicity
Allergic Reactions
Methemoglobin formation
Systemic toxicity: Results from effects of LA on excitable
membranes and tissues other than
target nerves
-Manifest first as CNS toxicity then cardiotoxicity (rule
of thumb)
CNS Toxicity
>Tinnitus, perioral numbness, blurred vision, metallic taste, change in mental state, convulsions.
Cardiotoxicity
>Depression of excitability and
(ventricular prolonged QRS) as well as arteriolar dilation (Calcium channel effect)
> Bupivacaine is very cardiotoxic (R+)
> Ropivacaine less toxic (S-)
> Systemic acidosis or hypercarbia increased sensitivity to LA toxicity (their pH is more acidic, trapping the LA in circulation)
>Pregnancy sensitivity to toxic effects **Rescue is by IV Lipid Emulsion (drawing the lipophilic drugs out)
Local injury:
Neural Injury
High concentrations of local for extended periods can lead to nerve tissue destruction via membrane damage, cytoskeletal disruption, etc. but not due to blockade of the Na channel
-Motor and sensory loss are seen (e.g. cauda equina syndrome): If patients with cauda equina syndrome do not receive treatment quickly, adverse results can include paralysis, impaired bladder, and/or bowel control, difficulty walking
-Paralysis and paresis may result
*Transient Neurologic Symptoms (TNS)
Transient pain syndrome associated with spinally administered Lidocaine and certain surgical positions (e.g. lithotomy)
**NOT associated with motor or sensory loss, it just hurts! A self limited neuropathic pain syndrome
Esters
>PABA ® hapten formation ® true IgE mediated allergy
Amides
-do not form the same metabolites and *Methylparaben, preservative, can cause allergic reactions irrespective of LA type
Prilocaine metabolites (O-toluidine)
act as an oxidizing agent to convert
Hb++ to Hb+++
Benzocaine has also been implicated Chocolate colored blood
Pulse oximeter = 85% saturation w Treatment is with methylene blue
Understand the concept of methemoglobinemia as it relates to LA’s
Prilocaine metabolites (O-toluidine)
act as an oxidizing agent to convert
Hb++ to Hb+++
Benzocaine has also been implicated
Chocolate colored blood
Pulse oximeter = 85% saturation
Treatment is with methylene blue
What are the mechanisms of opioids (assuming mew opioid)
Presynaptic neuron
• Inhibits adenylyl cyclase-catalyzed formation of cAMP [cAMP]↓
•Closes Ca2+ channels [Ca2+]↓
→ ↓ synaptic transmission
→ ↓ release of neurotransmitters
that convey pain perception (e.g., ACh, substance P, glutamate)
Postsynaptic neuron • Opens K+ channels [K+]↑ → hyperpolarization of cell • ↓ firing of neuron • ↓ neuron excitability & pain \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_