Highlights – May 7, 2014
Guest Speaker – Dr. Michael Pro
Lorraine Miller – Editor, Chat Topic Researcher
Moderator: This evening’s chat is “Glaucoma Medications.” Welcome back, Dr. Pro! Thanks for being here!
Dr. Pro: Great to be here!
P: Have you observed a loss of IOP control in patients who have switched from a brand name medication to a generic medication?
Dr. Pro: That is a difficult question to answer. There is an inherent fluctuation in a person’s intraocular pressure (IOP) from one visit to the next. When a person switches from a branded drop to a generic version, it can be difficult to determine if a change in IOP is a true change. However, there is some anecdotal evidence to suggest that generics may have a less consistent effect than the branded medicines.
P: I was on the original latanoprost and then was prescribed the generic one and found very little difference. How have your patients found the switch from Xalatan to latanoprost?
Dr. Pro: I cannot say that I have noticed a big difference in my patients. That being said, there is some anecdotal evidence in the glaucoma community that generics may be less effective in some persons than branded medications.
P: How prevalent is depression caused from glaucoma medication?
Dr. Pro: There are a number of side effects that have been attributed to medications, but most are infrequent. Depression is a very infrequent side effect that has been attributed to topical beta blockers like timolol.
P: How do we know if our low or down feelings are caused from glaucoma medication?
Dr. Pro: That is a really tough question to answer with certainty. If the symptoms were only present after the drop was begun then I would suggest questioning your ophthalmologist about the potential for this problem. The drop could be discontinued for a time to see if your mood improves under the care of your treating ophthalmologist.
P: Which classification of drugs could cause irregular heart rhythms?
Dr. Pro: Once more the beta blockers like timolol are to blame for this potential side effect. The confusing issue is that timolol is also found in certain fixed combination drops like Cosopt and Combigan.
P: Do any of the glaucoma medications cause sexual problems?
Dr. Pro: The beta blockers like timolol can cause male impotence.
P: How common are periorbital effects of prostaglandins?
Dr. Pro: I do not know the exact frequency of periorbital fat atrophy. Anecdotally, I think it affects less than a quarter of the patients treated with this class of drops. This side effect and others such as periocular darkening can be a cosmetic issue. This class of medications is very safe and well tolerated.
P: Does glaucoma medication affect our longevity?
Dr. Pro: This is a difficult question to answer as there are many factors that contribute to longevity. In general, I think there is no evidence that most glaucoma drops contribute to decreased longevity. The exception may be beta blockers like timolol in patients who have serious cardiovascular or pulmonary disease.
P: What damage is caused to our cardiovascular or respiratory system due to the long time use of glaucoma medication?
Dr. Pro: No irreversible damage is done. However, topical beta blockers can inhibit cardiovascular or pulmonary function in certain individuals. Even in healthy individuals, the heart rate can be slowed slightly (-5 beats per minute) by timolol.
P: Does impaired trabecular meshwork drainage in non-genetic open-angle glaucoma share pathological characteristics with atherosclerosis?
Dr. Pro: In atherosclerosis, cholesterol plaques build up in the vessels, whereas the reason for decreased aqueous outflow is not fully understood in glaucoma.
P: With the polar vortex we have experienced this winter, medication could freeze in a mailbox or freeze if left in a car. Can glaucoma medication be thawed and then used?
Dr. Pro: Glaucoma medications cannot be thawed and then used. There is a range at which glaucoma medications can be stored. This is somewhat specific to the medication and the exact range can be obtained by contacting the manufacturer. The range is somewhere above freezing and below 100 degrees. The efficacy of medications stored at length of times in conditions above or below those cut-offs cannot be guaranteed.
P: As you prescribe different classifications of drops for a patient, at what point do you realize the patient will inevitably require glaucoma surgery? Do you know after you see the response of the eye after just one prescription medication?
Dr. Pro: Every patient is different. Due to various risk factors, some patients need a lower IOP more than others. Drops or lasers are attempted prior to glaucoma surgery unless there is uncontrolled pressure and a real risk of rapid loss of vision.
P: Some patients start a new drug and within months, the drug seems to stop working. If a trabeculectomy or tube shunt surgery is performed and the need of glaucoma medication resumes, does the medication work differently due to the surgery or do the same problems exist as before the surgery?
Dr. Pro: Sometimes glaucoma surgery is performed and then the patient has to go back on drops. This does not mean that the glaucoma surgery was a failure. In fact, I frequently find that patients with tube shunts may need a glaucoma drop to maintain a target IOP. In a sense, the drops act in synergy with the surgery. The surgery helps to improve aqueous outflow and the drop decreases aqueous production. Before surgery there is an insufficient outflow and the drops cannot overcome this problem.
P: Dr. Pro, I have low tension glaucoma and adult onset asthma and have been prescribed a steroid inhaler which I am concerned about as I understand increased pressure from a steroid can sometimes not be reversed when the steroid is stopped. Is this true? Also, how does asthma affect glaucoma?
Dr. Pro: These are good questions. Asthma does not affect glaucoma directly. It is true that steroids can increase the IOP, but this effect is much less common with inhaled steroids as the dose is small and the medication is localized. I advise my glaucoma patients to have their pressure checked about one month after starting the inhaled steroid and then more frequently for at least a year after being on the medication to ascertain that the IOP is not affected.
P: Could some patients with clinically diagnosed open angle glaucoma also have angle closure glaucoma?
Dr. Pro: There are some patients in whom the diagnosis is less certain. They may have some areas of the angle closed, but most of the angle is not so they may be classified as open angle. There are also some patients who have a narrow angle and get a laser which is successful in opening up the angle. They may then later go on to develop open angle glaucoma. We sometimes call this mixed mechanism glaucoma.
P: Medical marijuana use for glaucoma is becoming more available through the United States. Has the increased usage in the glaucoma community had a positive effect on individuals’ IOP and progression of vision loss?
Dr. Pro: The American Glaucoma Society does not advocate the use of marijuana as a treatment for glaucoma as the IOP lowering effect is modest and wears off quickly. The intoxicant effect of smoking marijuana would prohibit its use for most individuals who need to function normally during the day. Also, the effect of the marijuana smoke is unknown in individuals with glaucoma.
P: During our last discussion on glaucoma medications, you commented, “Anecortave Acetate is an angiostatic steroid that has shown some promise as a treatment for open angle glaucoma in the form of an injection. I am fortunate that I hope to be working with this medication in trials soon.” Could you share with us the results of this trial?
Dr. Pro: That development of that medication and its progress to the market has stalled. I would assume this is because it has not proven to be as effective in the treatment of glaucoma as the pharmaceutical researchers had hoped. I have not heard of this medication in relation to glaucoma in several years.
P: You also made a reference to other research. “Santen is working on an angiotensin II antagonist. Pfizer is working with another company on a prostaglandin with nitric oxide donating properties. Biovitrum (Swedish Company) is working on a serotonin receptor antagonist.” Have any of these companies had positive results?
Dr. Pro: The most successful seems to be the prostaglandin with the nitric oxide component. This is like a turbo-charged Xalatan (latanoprost). Clinical trials have seen about a one mmHg greater IOP lowering effect of this agent versus standard latanoprost.
P: What is new on the horizon for glaucoma medication?
Dr. Pro: The prostaglandin with the nitric oxide component is most likely to reach the market. Another class of medications that may reach the market some day is the Rho Kinase inhibitors. There are various on-going clinical trials involving these agents. They work by improving aqueous outflow. The other new development is research into longer acting glaucoma drug injections into the eye or sustained release mediums like punctal plugs or drug delivery devices that rest in the space between the eye and the lid.
Moderator: Thank you, Dr Pro! Thanks to those who joined us this evening.