AMD Drugs (Tropicamide and Ranibizumab) Flashcards
What is tropicamide used to do?
Used to dilate the pupils by relaxing the pupillary sphincter. This lets the doctor look at the back of your eye more easily - allowing them to diagnose AMD or other eye conditions - as well as relieving some of the symptoms.
What is the pupillary sphincter?
A circular muscle of the iris and ciliary muscles. It is 1mm wide and consists of smooth muscle fibres.
What does the pupillary sphincter do?
When contracting during bright light, the pupillary sphincter constricts the pupil, which is called miosis. This action happens during accommodation and pupillary light reflexes.
What type of drug is tropicamide?
an alkaloid atropine‐derived anticholinergic drug and is a non-selective muscarinic receptor antagonist
What receptors do tropicamide work on?
muscarinic acetylcholine (mACh) receptors
What are Anticholinergic drugs or alkaloids?
competitive inhibitors of muscarinic receptors.
What is a non-selective antagonist of muscarinic receptors?
Block/inhibit all muscarinic receptors in the body, such as those in the heart, bladder, and intestine, not just those found in the brain. And also works on all subtypes including M1, M2, and M3 receptors.
What do muscarinic receptors do?
when acetylcholine binds to and stimulates these receptors, the muscles and vessels of the eye contract, causing the pupil to get smaller. (so preventing this interaction via antagonist drugs allows the pupil to dilate by blocking this action.)
How long does tropicamide last?
Effects last 4-24hrs
Is tropicamide an agonist or antagonist?
[non-selective] antagonist
What kind of antagonist is tropicamide?
non-selective muscarinic antagonist
What is a parasympathetic antagonist?
drugs that oppose the actions of the PNS at the muscarinic receptors by blocking the actions of acetylcholine. They are also referred to as anticholinergics or parasympatholytics.
What does Acetylcholine do?
Acetylcholine is a neurotransmitter that plays a major role in voluntary and involuntary muscle movement all over your body. It causes nerve cells to stimulate muscle nerve cells, causing muscles to contract.
What part of the eye can the M3 subtype of muscarinic acetylcholine receptors be found in?
The M3 subtype is predominantly expressed by smooth muscle cells of the sphincter pupillae/pupillary sphincter, which is a circular muscle of the iris, and ciliary muscles.
What is the role of M3 receptors in the pupillary sphincter/sphincter pupillae?
In response to light or binding of acetylcholine, M3 receptor signalling leads to contraction of the pupillary sphincter and pupil constriction.
Why is tropicamide a non-selective muscarinic antagonist?
It binds to all subtypes of muscarinic receptors all over the body
How does tropicamide dilate the pupils [FULL]?
By binding to muscarinic receptors, tropicamide relaxes the pupillary sphincter muscle and causes pupil dilation. This is because tropicamide is a antagonist drug, so it inhibits the muscarinic acetylcholine receptors, preventing acetylcholine from binding and stimulating the receptor. This prevents the action of the receptor, meaning the pupillary sphincter muscle cannot contract and constrict the pupil, resulting in the pupil dilating.
In addition, tropicamide dampens the parasympathetic response, so the pupils would not constrict, but would instead dilate as part of the sympathetic response.
What is tropicamide’s effect on the sympathetic responses of the nervous system?
Like other muscarinic antagonists, tropicamide inhibits the parasympathetic drive, allowing the sympathetic nervous system responses to dominate.
In this case, the pupils would not constrict due to the dampened parasympathetic response, but would dilate as part of the sympathetic response.
What is the best website for all this?
easily this one: https://go.drugbank.com/drugs/DB00809
Side effects of tropicamide?
- Clumsiness or unsteadiness.
- fast heartbeat.
- flushing or redness of face.
- hallucinations (seeing, hearing, or feeling - things that are not there)
- increased thirst or dryness of mouth.
- skin rash.
- slurred speech.
- swollen stomach in infants.
blurred vision;
mild stinging of the eyes;
your eyes may be more sensitive to light;
dry mouth; or
headache.
How is tropicamide administered?
eye drops
Advantages of using eye drops to administer?
- Fast acting because its applied straight to the target area, unlike tablets.
- A preferred method of administration over injection (especially those into the eye - discomfort - therefore people wont adhere.) or over tablets.
Disadvantages of using eye drops to administer?
- More uncomfortable to do than taking tablets, especially when using eye drops for the first time, or with young children.
- Side effects causing discomfort - makes people less likely to adhere - the non adherence makes their diagnosed condition worse.
How might Tropicamide be used for AMD?
It allows doctors to see the back of the eye more clearly, allowing them to diagnose AMD.
What is Ranibizumab?
Ranibizumab is a humanized monoclonal antibody and VEGF-A antagonist used for the management of AMD. Ranibizumab is used to treat various ocular disorders with abnormal growth of blood vessels such as Wet AMD.
What is a humanized monoclonal antibody?
A type of antibody made in the laboratory by combining a human antibody with a small part of a rat monoclonal antibody.
What is a monoclonal antibody?
A type of protein that is made in the laboratory and can bind to certain targets in the body, such as antigens on the surface of cancer cells.
is ranibizumab antagonist or agonist?
Antagonist
What do ranibizumab inhibit/work on?
The receptor binding site of VEGF-A (Vascular endothelial growth factor A)
What is VEGF-A?
a glycoprotein implicated in the pathophysiology of age-related macular degeneration
What is ranibizumab used for?
Ranibizumab is used to treat various ocular disorders with abnormal growth of blood vessels such as Wet AMD. Ultimately, ranibizumab works to slow down the loss of vision and causes significant visual improvement in patients with wet age-related macular degeneration
What does VEGF do?
VEGF-A is a key regulator of vascular permeability and angiogenesis.
What is angiogenesis?
The development of new blood vessels.
How does Ranibizumab help wet AMD? [FULL]
Ranibizumab binds to the receptor-binding site of VEGF-A, preventing it from binding to its receptors - VEGFR1 and VEGFR2 - that are expressed on the surface of endothelial cells. This thereby prevents the formation of new blood vessels which causes wet amd, slowing the loss of vision experienced by people suffering with Wet AMD, and potentially improving their vision as well.
What is the Mechanism of action of Ranibizumab?
Ranibizumab binds to the receptor-binding site of VEGF-A, preventing it from binding to its receptors - VEGFR1 and VEGFR2 - that are expressed on the surface of endothelial cells.
Best website?
This one…
https://go.drugbank.com/drugs/DB01270
How is Ranibizumab administered?
Administered by intravitreal injection (an injection of a drug into the vitreous body - the jelly in the eye).
What is an intravitreal injection?
An intravitreal injection is an injection of a drug into the vitreous body (the jelly in the eye). It is given through the sclera (the white of the eye).
Why do two molecules of ranibizumab bind to one VEGF-A receptor-binding site?
As ranibizumab has one binding site for VEGF, two drug molecules bind to one VEGF receptor
Why doesn’t ranibizumab cause inflammation?
Ranibizumab lacks the Fc region of an antibody, which may prevent the drug from causing intraocular inflammation following intravitreal injection
Advantages of administration by intravitreal injection?
Administered straight to the target area (the eye) so its fast acting.
Bypasses first pass metabolism.
Does not cause inflammation because ranibizumab lacks Fc region of antibody.
Disadvantages of administration by intravitreal injection?
- People may be uncomfortable with having an injection into the eye - so not many people will choose to receive the treatment - makes it extremely hard to administer to children.
- Less convenient than eye drops
- More painful
- Irritation
- Danger of infection
what are the side effects of ranibizumab?
Increased redness in the eye.
Eye pain.
Cataract.
Vitreous (gel-like substance) detachment.
Vitreous floaters.
Moving spots in the field of vision.
Increased pressure in the eye.
Blindness.
bloody eye.
blurred vision or loss of vision.
decreased vision or other changes in vision.
disturbed color perception.
dry eye.
eye pain.
fainting.
When should you NOT take ranibizumab?
If you have an infection in or around the eye or if you are allergic to it.
What is the prescription name for ranibizumab?
LUCENTIS
In what case should you visit the doctor after taking ranibizumab?
If your eye becomes red, sensitive to light, or painful, or if you have a change in vision, call or visit your eye doctor right away.
What should you do if your eye becomes red, sensitive to light, or painful, or if you have a change in vision?
Call or visit your eye doctor right away.
