Medical Therapy for Glaucoma
1999

Below is a list of the types of medications used for glaucoma. Sometimes some of them are used concurrently, and others can NOT be used together. I thought this might give a good overview of the medical therapies used...and we know that while some dogs do well with medical treatment alone for glaucoma for a period of time, eventually most need surgery of some kind (laser or cryo to preserve vision, or evisceration or enucleation to relieve pain). But most of us start out on eye (or oral) medications, so here is an overview. Hope it helps.
Kerry

Medical Therapy for Glaucoma

Currently, five classes of drug are available for use in patients with glaucoma or elevated intraocular pressure. No perfect medicine has been developed - all have some side-effects. Moreover, in some patients, medication fails to reduce IOP adequately. It is important therefore to balance efficacy, tolerability and side effects on a patient-by-patient basis. 

The treatment program can change over the time that glaucoma is treated. In some cases the change is necessary because of an unwanted side effect from the medication. In other cases, prescribing a stronger drug or adding another medication is necessary to maintain control of the eye pressure. 


The most frequently used medical therapies include:

Ophthalmic Beta-Blockers lower pressure in the eye by reducing aqueous production. These drugs are divided into two classes: 1) nonselective beta-blockers (timolol, levobunolol, metipranolol, carteolol); and 2) beta 1 selective (betaxolol). The Alcon product in this class is BETOPTIC S® (betaxolol HCl) ophthalmic suspension 0.25%.

Carbonic Anhydrase Inhibitors also lower pressure in the eye by decreasing aqueous production. Carbonic anhydrase inhibitors are available as topically (dorzolamide and brinzolamide) or orally (acetazolamide, methazolamide). The topical forms are associated with fewer systemic side-effects than the oral forms and are better tolerated by many patients.
Alcon recently introduced AZOPT® (brinzolamide) ophthalmic suspension 1%.

Alpha-Agonists are still another class of medicine that lower pressure primarily by reducing the aqueous production. In addition, they also may have an effect on increasing the rate at which the fluid drains from the eye. The most frequently prescribed drugs in this class are the relatively selective alpha 2 agonists (apraclonidine, brimonidine) IOPIDINE® 0.5%
(apraclonidine) ophthalmic solution is manufactured by Alcon.

Miotics have been used for over 100 years to lower eye pressure. Miotics decrease IOP by increasing aqueous outflow through the trabecular meshwork. However, because of their ocular adverse effects (increased myopia, eye and brow pain, decreased vision and retinal problems), the use of miotics is declining. Examples of miotics include pilocarpine and carbachol. Alcon
brands include ISOPTO® CARPINE (pilocarpine HCl) ophtalmic solution, PILOPINE HS® (pilocarpine HCl) gel and ISOPTO® CARBACHOL (carbachol) ophthalmic solution.

Prostaglandin analogs work by increasing the uveoscleral outflow. Only one (latanoprost) is currently available in the US. It has the advantage of effectiveness in lowering eye pressure with once daily dosing. However, some patients experience an irreversible change in iris color and the long-term significance of this effect is currently unknown.

The following drugs are classified as 'Antiglaucoma Agents': 

• Acetazolamide
• Betaxolol
• Brimonidine
• Brinzolamide
• Carbidopa; Levodopa
• Carteolol
• Dorzolamide
• Dorzolamide; Timolol
• Epinephrine
• Latanoprost
• Levobunolol
• Loratadine; Pseudoephedrine
• Pilocarpine
• Timolol

OptiPranolol is an antiglaucoma drop plus a beta-blocker...Metipranolol (OptiPranolol®)

Available as:
OptiPranolol® ophthalmic solution metipranolol 3 mg/ml
Also contains benzalkonium chloride 0.004% as a preservative.

Dosage:
For the treatment of elevated intraocular pressure in patients with ocular hypertension or open angle glaucoma:

Ophthalmic dosage:
Adults: Instill 1 drop of 0.3% solution into the affected eye(s) twice daily.


Description: Metipranolol is an ophthalmic, non-selective beta-blocker used to treat chronic open-angle glaucoma or any other ocular condition where lowering the intraocular pressure is likely to be of therapeutic benefit including patients with ocular hypertension. It is similar to ophthalmic timolol in mechanism, onset, and duration of action. Metipranolol reduces elevated as well as normal IOP. In controlled studies of patients with intraocular pressure greater than 24 mmHg at baseline, metipranolol reduced the average introcular pressure approximately 20—26%. Metipranolol was approved December 1989.

Mechanism of Action: Metipranolol has no significant intrinsic sympathomimetic activity, and has only weak local anesthetic (membrane-stabilizing) and myocardial depressant activity. Metipranolol decreases the rate of aqueous production, thereby decreasing intraocular
pressure (IOP).

Contraindications/Precautions: AV block greater than first degree, cardiogenic shock, congestive heart failure, diabetes mellitus, hypoglycemia, overt cardiac failure, pheochromocytoma, renal failure, sinus bradycardia, thyrotoxicosis.

Drug Interactions: no significant interactions.

Adverse Reactions: abnormal vision, blepharitis, blurred vision, browache, conjunctivitis, cough, dizziness, edema, excessive lacrimation, eyelid dermatitis, fatigue, ocular irritation and discomfort, photophobia, sinus bradycardia, vertigo.

Adverse reactions from ophthalmic beta-blockers are usually limited to their ocular effects, such as transient burning, stinging, and blurred vision however, these preparations can be absorbed causing systemic adverse reactions, similar to oral or parenteral beta-blockers. Ophthalmic betaxolol appears to cause less systemic effects compared to ophthalmic
timolol and levobunolol.

Timolol
Betimol®, Blocadren®, Timoptic® | BETIMOL | BLOCADREN | TIMOPTIC | TIMOPTIC
IN OCUDOSE | TIMOPTIC-XE

For the treatment of elevated intraocular pressure in glaucoma or ocular
hypertension:

Ophthalmic dosage (Timoptic®):
Adults and children: Instill 1 drop of a 0.25% solution in affected eye(s) bid. Dosage may be increased to 1 drop of a 0.5% solution 2 times per day, if necessary for adequate reduction of intraocular pressure. Dosage may be reduced to 1 drop once daily of effective strength to maintain reduced pressure.

Ophthalmic dosage (Timoptic-XE™ gel forming solution):
Adults: Instill 1 drop of a 0.25% solution in affected eye(s) once daily. Dosage may be increased to 1 drop of a 0.5% solution once daily, if necessary for adequate reduction of intraocular pressure. Doses greater than one drop of the 0.5% solution once daily have not been studied.

Abrupt discontinuation of any beta-adrenergic blocking agent, including timolol, can result in the development of myocardial ischemia, infarction, ventricular arrhythmias, or severe hypertension, particularly in patients with preexisting cardiovascular disease. 

Description: Timolol is a nonselective, beta-adrenergic receptor antagonist similar to propranolol and nadolol. Timolol does not demonstrate appreciable intrinsic sympathomimetic or membrane-stabilizing activities. Like propranolol, timolol possesses a relatively high degree of lipid solubility and is subject to first-pass metabolism by the liver. Timolol is available for both systemic and ophthalmic use. Timolol was approved by the FDA for optical use in 1978, and for oral use in 1981. Under the General Agreement on Tariffs and Trade (GATT), the patents for Timoptic® and Timoptic-XE™ expired on September 26, 1995 and September 25, 1996, respectively.

Reduction of elevated or normal intraocular pressure occurs irrespective of the presence of glaucoma. This effect is believed to be caused by a reduced production of aqueous humor, although the exact mechanism has not been elucidated. Visual acuity, pupil size, and accommodation do not appear to be affected by timolol.

Similar to the characteristics of oral timolol, ophthalmic timolol reduces intraocular pressure within roughly 30 minutes following application, peaks 1—2 hours later, and can last 24 hours.

beta-blocking agents are pharmacological antagonists of sympathomimetics or adrenergic agonists. Administration of timolol with any sympathomimetic or adrenergic agonist could lead to antagonism of some or all of the therapeutic actions of the agents involved. Since timolol is a nonspecific beta-blocker, it should not be used with albuterol, metoproterenol, or other beta2-agonists; or epinephrine, norepinephrine, or other cardiovascular stimulants. NSAIDs can reduce the hypotensive effects of antihypertensives.

Oral Timolol is used as a beta-blocker - ophthalmic timolol is not nearly as strong as a beta-blocker and works much more locally than systemically.

Here is patient info (for humans) on Timolol:

What does timolol eye solution or eye gel-forming solution do?
TIMOLOL (Timoptic®, Timoptic-XE™) belongs to a group of medicines called beta-blockers. Timolol lowers increased pressures within the eye and is effective in treating certain types of glaucoma. Generic timolol eye solutions are available. Generic eye gel-forming solutions are not available generically.

What should my health care professional know before I use timolol?
They need to know if you have any of these conditions:
• asthma, bronchitis or bronchospasm, emphysema, or other lung disease
• contact lenses
• diabetes
• heart or blood vessel disease
• thyroid disease
• an unusual or allergic reaction to timolol, other beta-blockers, medicines, foods, dyes, or preservatives
• pregnant or trying to get pregnant
• breast-feeding

How should I use this medicine?
Timolol eye solution is only for use in the eye. Do not take by mouth. Follow the directions on the prescription label. If you are using a unit dose container, use immediately after opening and throw away right after use. If you are using the gel-forming solution, turn the container upside
down once to shake the contents before use. Wash hands before and after use. Tilt your head back slightly and pull your lower eyelid down with your index finger to form a pouch. Try not to touch the tip of the dropper to your eye, fingertips, or any other surface. Squeeze the prescribed number of drops into the pouch. Close the eye for a few moments to spread the
drops. Use your doses at regular intervals. Do not use your medicine more often than directed. Do not stop using except on your prescriber's advice.

Contact your pediatrician or health care professional regarding the use of this medicine in children. Special care may be needed.

What if I miss a dose?
If you miss a dose, use it as soon as you can. If it is almost time for your next dose, use only that dose. Do not use double or extra doses.

What other medicines can interact with timolol?
• atropine
• clonidine
• ergotamine
• medicines for high blood pressure
• medicines for colds and breathing difficulties
• medicines for diabetes
• medicines for mental depression
• medicines for mental problems and psychotic disturbances
• medicines to control heart rhythm
• theophylline

Do not use other eye products with timolol without asking your prescriber
or health care professional.

What side effects may I notice from using timolol?
Side effects with timolol eye products include:
• burning stinging or itching of the eyes or eyelids
• changes in vision
• increased sensitivity of the eyes to light

Other side effects from the use of timolol eye products are uncommon. Side effects that you should report to your prescriber or health care professional as soon as possible:
• changes in blood sugar
• cold hands or feet
• confusion, hallucinations (seeing and hearing things that are not really there)
• difficulty breathing, wheezing
• difficulty sleeping, nightmares
• dizziness or fainting spells
• irregular heartbeat, palpitations, chest pain
• skin rash, itching, peeling skin
• slow heart rate (less than 50 beats per minute)
• swelling of the legs or ankles

What do I need to watch for while I use timolol?
Visit your prescriber or health care professional for regular eye pressure exams. Ask your prescriber or health care professional if you should continue to use timolol if you injure your eyes, get an eye infection, or need eye surgery.

You may get drowsy or dizzy. Do not drive, use machinery, or do anything that requires mental alertness until you know how timolol affects you. To reduce the risk of dizzy or fainting spells, do not sit or stand up quickly. Alcohol can make you more drowsy, and increase flushing and rapid heartbeats. Therefore, it is best to avoid alcoholic drinks.

If your eyes become more sensitive to light while using timolol eye solution, stay out of bright light and wear sunglasses.

If you are using the gel-forming solution, use any other eye medicine you are prescribed at least 10 minutes before timolol.

If you wear soft contact lenses, you should not put timolol eye drops in your eyes while wearing the lenses. After using the eye drops, wait about 15 minutes before putting lenses in your eyes.

Where can I keep my medicine?
Keep out of the reach of children in a container that small children cannot
open.

Store at room temperature between 15 and 30 degrees C (59 and 86 degrees F).
Protect from light. Keep container tightly closed. After opening the foil wrap of unit dose eye drops (Ocudose®), use within 1 month. Throw away any unused medicine after the expiration date.

NOTE: This information is not intended to cover all possible uses, precautions, interactions, or adverse effects for this drug. If you have questions about the drug(s) you are taking, check with your health care professional.

 

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