Quiz 2 Exam 3 Flashcards
Where is a periocular injection?
Injection given around the eye but not directly in it. The drug will diffuse into the eye.
Where is a subconjunctival injection?
Injection below the conjunctiva of the eye.
Where is an intravitreal injection?
This goes into the vitreous humor through the pars plana region of the eye.
T or F: Intraocular pressure increases due to aqueous humor which decreases the risk of glaucoma.
False. Increases in intraocular pressure increase the risk for glaucoma by accelerating cell death in the optic nerve.
What are the two discussed topical antibacterials used for eye infections?
Moxifloxacin (Vigamox) and Gatifloxacin (Zymar)
What was a topical anti inflammatory used for eye inflammation?
Loteprednol (Lotemax)
What is a topical drug used on the eyes for dry eye disease?
Cyclosporine (Restasis, Cequa)
What is dry eye disease and what causes it?
Dry eye disease is dysfunctional tear syndrome due to loss of homeostasis of the tear film due to reduced tear production or increased evaporation.
What are the 3 things that should be used for dry eye disease?
Artificial tears
Topical corticosteroid
Cyclosporine
What were the different posterior eye diseases discussed?
Uveitis, macular edema, diabetic retinopathy, age-related macular degeneration (AMD), endophthalmitis, and glaucoma.
What is uveitis?
This is inflammation of the uvea of the eye. The uvea goes around the entire eyeball. If uveitis is left untreated, it will lead to blindness.
How is uveitis treated?
Topical application of corticosteroid (for anterior) or systemic / injection of corticosteroids for posterior.
T or F: Topical applicable of drugs into the eye works well for both anterior and posterior eye disease.
False. Eye drop medications only work for anterior eye disease.
What is macular edema?
The retinal thickening near the fovea or hard yellow exudates near the fovea.
What is the function of the fovea of the eye?
It allows for fine vision and requires a smooth retina to produce the fine vision effects.
What are the two types of diabetic macular edemas?
Focal and diffuse
What is a focal diabetic macular edema?
This is when leaking blood vessels are causing the blindness.
What is diffuse diabetic macular edema?
This is when there is dilation of the retinal capillaries throughout the back of the eye which is leading to blindness.
What is the treatment for macular edema?
Laser photocoagulation
or
Corticosteroids
or
anti-VEGF
What is diabetic retinopathy?
This is a neovascular disease. In a general sense, there is abnormal growth of new blood vessels in the retina and they break and leak leading to vision loss.
How is diabetic retinopathy treated?
Laser and anti-VEGF or in very severe cases a vitrectomy to remove the blood in the eye.
What are the two forms of age-related macular degeneration (AMD)?
Dry and wet
What is dry age-related macular degeneration (dry AMD)?
This is when there are fatty deposits under the light-sensing cells in the retina.
What is wet age-related macular degeneration (wet AMD)?
This is choroidal neovascularization with growth of tine new blood vessels under the retina that leak fluid or break open.
Is dry or wet age-related macular degeneration more serious?
Wet AMD is more serious.
What is the treatment for dry age-related macular degeneration?
AREDS supplement (vitamins and omega-3 FA) or complement proteins C3 and C5 inhibitors.
What is the treatment for wet age-related macular degeneration?
Laser treatment to destroy blood vessels and/or anti-VEGF.
What are some of the main anti-VEGF drugs discussed?
Lucentis (Ranibizumab), Eylea (Aflibercept), Avastin (Bevacizumab)
Know where drugs are absorbed and cleared from the anterior portion of the eye.
Understand the distribution of drugs in the eye.
Explain drug delivery across the cornea of the eye.
Non-polar/uncharged drugs pass transcellular through cornea to enter aqueous humor while polar/charged drugs pass paracellularly.
What is the normal aqueous humor volume?
310 microL
What is the aqueous humor turnover rate?
1.53 microL/min
What is the blinking rate?
15x/min
In general, less than ______% of eye drops get into the eye and most just enters systemic circulation.
5
________ and ________ in eyedrops can increase retention and absorption of eye drops.
Bioadhesion and polymers
T or F: Drugs given via eye drops have a long tmax.
False. Topical eye medications have a short tmax due to high clearance in the eye and fast turnover of aqueous humor.
What are the 5 main things that decrease the effectiveness of topical eye drops?
- Less than 5% reaches anterior chamber
- Precorneal tear clearance
- Cornea and conjunctiva barrier
- Drug loss through clearnace
- Patient compliance
What was the first FDA approved ocular device?
Ocusert and it was for elevated intraocular pressure.
Know where drugs are absorbed and cleared in the posterior portion of the eye.
What are the static and dynamic barriers of the eye?
Static barriers: tissues, layers of cornea, sclera, retina, and blood aqueous barrier
Dynamic barriers: blood flow, tear dilution, and lymphatic clearance
What is the most common drug delivery for posterior eye diseases?
Intravitreal injection as drops, systemics, and transscleral things do not work here.
Are suspensions or solutions of eye injection drugs used for acute issues?
Solutions. Small doses given around 0.4mg
Are suspensions or solution of eye injection drugs used for chronic disease?
Suspensions. Large doses given around 4mg
What was the one corticosteroid solution that was discussed?
Dexamethasone phosphate. Used in acute conditions like swelling of eye tissue.
What was the one corticosteroid suspension that was discussed?
Triamcinolone acetonide. Used in chronic disease states like uveitis and macular edema.
What are the two main adverse effects of intraocular corticosteroid injections?
Cataract progression and elevated intraocular pressure.
note: intraocular and intravitreal are the same thing
Why is avastin (Bevacizumab) being used off-label as an anti-VEGF instead of lucentis (ranibizumab)?
Both have the same MOA but it is shown that Avaastin has a slower clearance and longer duration of action and it a lot cheaper. There were no difference in outcomes in AMD between the two drugs.
What are the main side effects of intravitreal injections in general?
Endophthalmitis, retinal detachment, traumatic cataract, and vitreous hemorrhage.
There is a high chance of experiencing these as injections need to be given more than once typically.
Does lucentis or photodynamic therapy work better in the treatment of AMD?
Lucentis works better than photodynamic therapy for AMD and preserves eye sight.
What are the two types of eye implants?
Non-biodegradable and biodegradable that go into the pars planar region of the eye.
What are the 5 general components of general anesthesia?
Analgesia (lack of pain)
Amnesia
Loss of consciousness
Inhibition of autonomic reflexes
Skeletal muscle relaxation
Anesthesia acts through the ____________ neural pathway.
Spinothalamic
What is the preferred inhaled anesthetic?
Sevoflurane
T or F: Inhaled anesthetics like Nitrous oxide, sevoflurane, halothane, and more have a very wide therapeutic index.
False. Inhaled anesthetics have a very narrow therapeutic index.
The depth of the anesthesia (intensity of the drug) depends on it concentrations in the __________.
CNS
Inhalation of anesthetics requires the transfer from the ______ of the lungs, to the blood, and then to the brain.
Aveoli
Concentration of an individual gas in a mixture of other gases is proportional to it _________ __________.
Partial pressure
What are the two main factors that determine the diffusion of gases in fluid and tissue?
Partial pressure and solubility
The amount of a given gas dissolved in liquid is directly proportional to the ______ _______ of the gas in contact with that liquid.
Partial pressure
As partial pressure of the gas increases , the ________ of gas in liquid increases.
Amount
As partial pressure increases, the amount of gas dissolved and the drug ___________ also increases.
Concentration
A highly soluble gas will have a ______ partial pressure in the air.
Low
As the solubility of a gas increases, the partial pressure __________ in the air.
Decreases
A ______ blood:gas coefficient means that the anesthetic does not dissolve well in blood therefore the onset of that anesthetic will be _________ as it reaches the CNS faster.
Low
Faster
A ________ blood:gas coefficient means that the anesthetic dissolves more in the blood and _______ drug is needed for it to reach the CNS.
High
More
T or F: Low blood:gas coefficient means slow onset.
False! Low blood:gas coefficient means rapid onset.
Does nitrous oxide have a low or high blood:gas coefficient? How does this impact its absorption?
NO has a low blood:gas coefficient meaning that is it less soluble in the blood. They dissolve less in the blood, the partial pressure in blood rises rapidly, quickly reaching a level that promotes diffusion into the brain. This leads to a faster induction of anesthesia.
Does halothane have a high or low blood:gas coefficient? How does this impact its absorption?
Halothane has a high blood:gas coefficient meaning it is more soluble in blood. This means more anesthetic is needed in the blood to achieve an effective partial pressure in the brain, which slows down the induction process. It takes longer for the anesthetic to reach the required level for anesthesia in the brain.
Is increasing ventilation rates used mainly for high or low blood:gas coefficient anesthetics?
High blood:gas coefficients as increasing respirations increases induction speed.
What is MAC?
MAC is the minimum alveolar concentration. It is the partial pressure of the anesthetic as a percentage of 760 mmHg resulting in the immobility of 50% of patients when exposed to the drug.
What does a low MAC value mean?
(ex: Halothane is 0.76)
A lower MAC value means the anesthetic is more potent, as a lower concentration is needed to achieve the desired effect.
What does a high MAC value mean?
(ex: Nitrous oxide is 105)
Nitrous oxide has a high MAC (over 100%), indicating it is less potent on its own.
Inhaled anesthetics with _______ blood:gas coefficients (insoluble in blood and brain) are eliminated at _______ rates than more soluble anesthetics.
Low
Faster
_______ blood:gas coefficients means ________ elimination.
High
Slow
Increased ventilation rates increases ________ concentration more for moderately soluble anesthetics like halothane.
Arterial
Blood:gas coefficient (solubility basically) are inversely proportional to _________.
Onset of action
High BG coefficient means highly dissolvable in blood which means slow entrance into the brain.
Low BG coefficient means not soluble in blood and faster entrance into the brain.
What is the most commonly used intravenous anesthetic?
Propofol
______ and ______ are used as adjuncts with anesthesia.
Opioids like fentanyl and neuromuscular blockers
What are the main 4 side effects of anesthetics?
- Decrease in blood pressure (direct vasodilation and suppression of cardiac activity and reduction of baroreceptors)
- Reduction in ventilation
- Hypothermia
- Nausea and vomiting (stimulates chemoreceptor trigger zone)
What are the 3 toxicities seen with inhaled anesthetics?
Hepatotoxicity (Halothane)
Nephrotoxicity (methoxyflurane and sevoflurane metabolized to toxic fluoride ions)
Malignant hyperthermia
What is the MOA for inhaled anesthetics, barbiturates (thiopental), BZs (Midazolam), and propofol?
Facilitating GABA actions at GABA A site by hyperpolarizing the neuron. They bind to GABA A site and cause the ion channel to open and let Chloride flow in. This influx of negatively charged ions makes the neuron more negatively charged (hyperpolarized), making it less likely to fire or send a signal.
What is the MOA of nitrous oxide, ketamine, and fluorinated hydrocarbons?
Inhibit glutamate function by binding and blocking NMDA receptors.
What explains the role of partial pressure and solubility of sevoflurane in determining the onset and depth of anesthesia?
The partial pressure of an anesthetic in the brain is directly proportional to the inspired concentration, assuming a steady-state equilibrium is reached.
What is the main difference between a local anesthetic and a general anesthetic?
Local anesthetics only induce pain relief local loss of sensation but no loss of consciousness.
Local anesthetics block impulse conduction by blocking _________ channels. This prevents afferent signal transmission of pain to the brain.
Sodium
Local anesthetics are derived from _______.
Cocaine
What are the two groups of most commonly used local anesthetics?
The amides which include long and medium acting. Long acting are bupivacaine and ropivacaine while medium acting is lidocaine.
What are the two types of local anesthetics?
Esters and Amides
Are the esters or amides for local anesthetics hydrophobic?
The amides are hydrophobic and have a longer duration of action.
Are the esters or amides for local anesthetics hydrophilic?
The esters are hydrophilic (cocaine, benzocaine, procaine), and have a shorter duration of action.
What happens when local anesthetics are systemically absorbed?
Their effect is diminished and they can cause toxicity.
Lipophilic local anesthetics, the amides, are more ________, have a ______ duration of action, and take longer to achieve their full clinical effect.
Potent
Longer
Why is epinephrine sometimes used in conjunction with local anesthetics?
Epinephrine limits the removal of local anesthetics, increases its duration of action, and limits toxicity by vasoconstricting blood vessels.
What is the only local anesthetic with intrinsic vasoconstrictive properties?
Cocaine. All other local anesthetics produce vasodilation.
The ________ form of local anesthetics like lidocaine are needed to be active but, the ________ form is needed for it to cross the cell membrane.
Charged
Uncharged
Do local anesthetics like lidocaine work outside the cell or inside the cell?
Inside the cell. They must be uncharged to pass into the cell and become charged to bind and block sodium channels.
Are local anesthetics like lidocaine more or less effective in a low pH site like an infected area?
Less effective in low pH areas as they need a high pH to become unionized and cross into the cell.
Nerve sensitivity to local anesthetics depends on what 3 things?
Firing rate
Size
Myelination
T or F: Slow firing neurons are blocked more effectively than fast-firing neurons.
False. Fast-firing neurons are blocked more effectively with local anesthetics.
T or F: Small diameter neurons are the first to be anesthetized.
True.
Size outweighs myelination so small myelinated nerves are blocked first, then small unmyelinated, then large myelinated, then large unmyelinated.
T or F: Unmyelinated nerves are blocked faster than myelinated nerves.
False. Myelinated are blocked faster as myelination increases the speed of action potentials.
What type of nerve is the first to go in response to local anesthetic administration?
Pain fibers
(then temp, touch, and pressure)
Injection of a local anesthetic in soft tissue within the vicinity of a nerve is called an _____________.
Infiltration
Injection into a major nerve trunk is called a ___________________.
Nerve Block
What is the most common adverse effect of systemic distribution of a local anesthetic?
Seizures
What is the MOA for cocaine?
Blocks reuptake transporters for dopamine, serotonin, NE, and epi therefore indirectly increasing the amount of the drug in the synapse. It also blocks sodium reuptake and vasoconstricts when acting as a topical anesthetic.
What is the MOA of lidocaine?
Lidocaine blocks voltage-gated sodium channels (VGSCs) in neurons, which prevents the transmission of action potentials and the sensation of pain.
What is the MOA of propofol?
Binds GABA A site on GABA receptor and increases it channel opening to let in more chloride leading to cell hyperpolarization.
What is the MOA of isoflurane?
This drug hyperpolarizes GABA A receptors and blocks glutamate NMDA receptors. (most -fluranes do this and halothane)
What are the 3 main adverse effects of a1 antagonists like silodosin, tamsulosin, and prazosin?
1st dose syncope, orthostatic hypotension, and reflex tachycardia.
