Pharm exam II- CNS depressants Flashcards
What NT is found in cell bodies at all neuro levels and causes EPSP at the muscarinic receptors?
Acetylcholine
What are some drugs acting at Ach receptors?
Atropine
Antiparkinsons drugs
Alzheimers drugs
The NT dopamine binds to which receptors (blank1) and causes what effect (blank 2)?
- Dopanergic receptors
2. IPSP
Drugs that work at Dopanergic receptors include?
Antipsychotic
Antiparkison
If a barbiturate is given to a patient who is acidotic what will it do to the drugs effects?
potentiate the effects because the active portion of barbs are weak acids even though they are alkalotic in solution. So acid in an acid will be unionized and can cross membranes more easily
What is important about when drawing up concentrations of barbs (thiopental and Brevitol)?
Should not be higher than recommended concentration or can cause tissue damage
Thio concentration = 2.5%
Metho concentration = 1%
Are barbs compatible with other drugs?
not very many. Will cause precipitation and sludge if combined with other acidic meds
What solution should barbs not be reconstituted with?
LR will precipitate
With oxybarbiturates what will a substitution at carbon 2 of a O2 with sulfur create?
Thiobarbital
Sulfarization= increased potentancy and increases lipid solubility
What will a branched chain on C5 do to barbs characteristics?
More hypnotic activity compared to a straight chain
A barb with a phenyl group on C5 will enhance what effects?
Anticonvulsant effects
Adding a methyl group to the N atom on barbs will do what?
Will impart convulsant effects and result in shorter duration = Methohexital (Brevial)
Brevital used in ECT therapy because does not prevent siezure activity while causing sedation
What is the MOA of barbs?
decreases rate of dissociation of GABA from receptor which depresses RAS by opening Cl- channels longer (enhances GABA)
Barbs and propofol both will have decreases in BP but what is different in each?
Barbs decrease in BP due to SNS depression= vasodilation
Propofol decrease in BP due to Myocardial depression
Rapid awakening from Thiopental is result of what?
Redistribution out of brain (very lipid soluble)
Is Thiopental and other barbs good drugs for IV infusions?
No because of accumulation effects that can linger in fat and muscle tissue
What is the pKa of Thiopental and what is the pH of the solution after reconstituting?
pKa= 7.5 (close to normal physiologic pH) pH= 10.5 very alkalotic can cause tissue damage
When considering kinetics what is important to know about Thiopental?
It is highly lipid soluble and protein bound so drug will be enhanced from displacement from proteins from other drugs or low albumin states.
How quick does Thiopental and Methohexital reach reach equilibrium (max brain uptake)?
within 60 secs
If patient has low cardiac output how can this affect an induction dose?
May take longer than normal to circulate to brain so be patient and don’t redose to quickly or may drop bp too much
How should you calculate most induction doses?
Lean body mass
women= 105 + (5lbs for each in over 5ft) men= 106 + (6lbs for each in over 5ft)
Who would wake up quicker after giving a barb, an enzyme induced drug abuser or renal failure patient?
Both will wake up about same time because context sensitive time is based off redistribution not elimination.
What are some clinical uses for Barbs?
- induction of Anesthesia
- sedation
- **tx of increased intracranial pressure related to decreased CBF
- anticonvulsant
In higher doses barbs will do what to an EEG in comparison to versed?
- barbs will produce isoelectric line in EEG in high doses
- versed decreases CMR02 and CBF but has ceiling effect and will not produce isoelectric EEG like barbs
What do barbs do to hepatic enzymes?
Will cause enzyme induction after prolonged use of barbs
Drugs that increase activity of the hepatic CP-450 system such as barbs can cause what in certain populations?
Acute Intermittent Porphyria= genetic disorder found more in northern European women that accelerates heme production and is often manifested as abdominal pain, peripheral neuropathies, and psychiatric symptoms
What will happen if a barb is injected into an artery?
- intense vasoconstriction and pain
- tissue damage and loss of pulse
How would you manage intra-arterial injection of barbs are caustic drugs?
- dilute to avoid spasm and maintain flow
- Give lidocaine
- Give alpha blocker (phenoxybenzamine)= vasodilator
- Give Urokinase to break up clots
- Possible Stellate ganglion block to manage vasoconstriction
What is the concentration of propofol?
1%= 10mg/ml
What food allergies might be a concern when giving propofol?
Eggs and soy because propofol made from egg and soybean solutions
What is important to note about length of administration when giving propofol?
- supports bacteria growth
- should be refrigerated
- can be at room temp for 12 hrs**
- can also cause Propofol infusion syndrome >5hrs (more to come)
How does propofol cause its effect at the receptor binding site?
- Decreases rate of dissociation of GABA from receptor (Same as barbs) therefore increases duration of opening of Cl- channels (IPSP) causing hyperpolarization of cell membranes
Propofol is almost ideal infusion agent when considering kinetics why?
- undergoes rapid hepatic metabolism
- short duration of action
- rapid wake up time (context sensitive time)
- highly lipid soluble so rapid brain uptake (equilibration)
- ** decreased NV**
- less hangover effects
What are other uses for propofol other than sedation and anesthesia?
- Antiemetic 10mg bolus
- Antipruritic 10mg
- Anticonvulsant
CNS effects of Propofol?
- decreased CMRO2, CBF, and ICP (good neuro)
- May decreased CPP as result of bp drop
- Decreases SSEP’s as seen in barbs
What can propofol do to sense of well-being?
Can make you feel amorous (sexy)
Propofol cardiovascular effects?
- Inhibits baroreceptor reflex
- decrease BP (> than thiopental) due to myocardial depression
- Decreased *CO and SVR
- May decrease HR
- Blunts CV effects of laryngoscopy (reduces increases in HR, BP, ICP)
What drugs are better to blunt CV effects of laryngoscopy?
- Fentanyl
- Lidocaine IV bolus or topical spray (Laryngeal tracheal Anesthesia kit (LTA))
- Esmolol
Not in kids though because HR decreases so atropine given to blunt
Rapid and shallow breathing could be sign of what drug on board?
Muscle relaxants
Slow and deep breathing is result of what type of drug?
Opioids
Slow and Shallow breathing could be caused by what drug?
Propofol
What is the most common complaint about propofol?
Pain on injection (give in large vein or give lidocaine prior)
What is Propofol Infusion syndrome?
Impaired oxidation of fatty acids and oxidative phosphorylation in mitochondria leading to lactic acidosis and muscular necrosis after using propofol for extended periods of time (seen after 5 hrs but usually recommended to limit <48hrs)
What are clinical effects of propofol infusion syndrom?
- hyperkalemia
- hepatomeglia
- lipidemia
- metabolic acidosis
- myocardial failure
- rhabdo
What is fospropofol (Lusedra)?
- Prodrug that is water soluble and is hydrolyzed into propofol
- Its onset is slowed and has a prolonged duration in comparison to propofol (may lead to more abuse)
What is the major side effect of fospropofol?
Perineal itching
Does fospropofol cause pain on injection like propofol?
No
What are some of the characteristics of Etomidate?
- carboxylated imidazole ring which gives with lipid solubility
- May cause pain on injection if contains propylene glycol
- Large Vd
- rapid brain uptake (equilibration)
- Highly protein bound (76%)
- fast awakening
How is Etomidate metabolized?
Rapidly metabolized by liver and plasma by ester hydrolysis to inactive metabolites
What is Etomidate mostly used for?
- Induction agent (drug of choice for myocardial depressed inductions)
- Infusion (rare)