Istalol Side Effects

Generic Name: timolol ophthalmic

Note: This page contains information about the side effects of timolol ophthalmic. Some of the dosage forms included on this document may not apply to the brand name Istalol.

Not all side effects for Istalol may be reported. You should always consult a doctor or healthcare professional for medical advice. Side effects can be reported to the FDA here.

For the Consumer

Applies to timolol ophthalmic: ophthalmic gel forming solution, ophthalmic solution

In addition to its needed effects, some unwanted effects may be caused by timolol ophthalmic (the active ingredient contained in Istalol). In the event that any of these side effects do occur, they may require medical attention.

You should check with your doctor immediately if any of these side effects occur when taking timolol ophthalmic:

More common
  • Blurred vision
  • burning or stinging in eye
Less common
  • Arm, back, or jaw pain
  • blisters, hives, welts, or itching
  • blue lips, fingernails, or skin
  • burning, crawling, itching, numbness, prickling, "pins and needles", or tingling feelings
  • change in vision
  • chest pain or discomfort
  • chest tightness or heaviness
  • confusion about identity, place, and time
  • continuing ringing or buzzing or other unexplained noise in ears
  • coughing that sometimes produces a pink frothy sputum
  • depression
  • difficult, fast, noisy breathing, sometimes with wheezing
  • difficulty in chewing, swallowing, or talking
  • dilated neck veins
  • discharge, excessive tearing
  • disturbed color perception
  • dizziness, faintness, or lightheadedness when getting up from a lying or sitting position suddenly
  • double vision
  • drooping eyelids
  • dry or itching eyes
  • extreme fatigue
  • false sense of well-being
  • fast, slow, irregular, pounding, or racing heartbeat or pulse
  • fear, nervousness
  • feeling of having something in the eye
  • fever and chills
  • flashes of light, floaters in vision
  • general feeling of discomfort or illness
  • hair loss
  • halos around lights
  • headaches
  • inability to speak
  • increased sweating
  • irregular, fast or slow, or shallow breathing
  • large, hive-like swelling on face, eyelids, lips, tongue, throat, hands, legs, feet, or sex organs
  • lightheadedness, dizziness, or fainting
  • loss of vision
  • memory loss
  • mood swings
  • muscle or joint pain
  • muscle weakness
  • nausea
  • night blindness
  • no blood pressure or pulse
  • overbright appearance of lights
  • pain, tension, and weakness upon walking that subsides during periods of rest
  • pale skin
  • paleness or cold feeling in fingertips, toes, hands, and feet
  • personality changes
  • pounding in the ears
  • puffiness or swelling of the eyelids or around the eyes, face, lips, or tongue
  • redness of skin
  • redness, pain, swelling or irritation of eye, eyelid, or inner lining of eyelid
  • seeing double
  • seeing, hearing, or feeling things that are not there
  • seizures
  • severe numbness, especially on one side of the face or body
  • severe or sudden headache
  • severe tiredness
  • shortness of breath or troubled breathing
  • skin irritation or rash, including rash that looks like psoriasis
  • slurred speech
  • sore throat
  • stopping of heart
  • sweating
  • swelling of face, fingers, feet, lower legs, and ankles
  • swollen glands
  • temporary blindness
  • tingling or pain in fingers or toes when exposed to cold
  • tunnel vision
  • unconsciousness
  • unusual tiredness or weakness
  • weakness in arm and/or leg on one side of the body, sudden and severe
  • weight gain
  • wheezing

Some of the side effects that can occur with timolol ophthalmic may not need medical attention. As your body adjusts to the medicine during treatment these side effects may go away. Your health care professional may also be able to tell you about ways to reduce or prevent some of these side effects. If any of the following side effects continue, are bothersome or if you have any questions about them, check with your health care professional:

Less common
  • Acid or sour stomach
  • belching
  • body aches or pain
  • diarrhea
  • dry mouth
  • ear congestion
  • hearing loss
  • heartburn
  • indigestion
  • lack or loss of strength
  • loss of appetite
  • loss of voice
  • nightmares
  • runny nose
  • sleepiness or unusual drowsiness
  • sleeplessness
  • sneezing
  • stomach discomfort, upset, or pain
  • stuffy nose
  • trouble sleeping
  • unable to sleep
  • weight loss

For Healthcare Professionals

Applies to timolol ophthalmic: ophthalmic gel forming solution, ophthalmic solution


Topically applied timolol ophthalmic (the active ingredient contained in Istalol) drops may be absorbed systemically and side effects similar to systemically administered timolol or other beta-blockers such as severe respiratory or cardiac reactions may be experienced.

In clinical trials, timolol ophthalmic solution and gel forming solution had a similar incidence of side effects.


Ocular side effects have included burning and stinging upon instillation, which has been reported in approximately 12% of patients receiving timolol ophthalmic (the active ingredient contained in Istalol) drops. Signs of ocular irritation including but not limited to conjunctivitis, blepharitis, keratitis, ocular pain, discharge/crusting, foreign body sensation, itching, tearing, and dry eyes. Ptosis, decreased corneal sensitivity, cystoid macular edema, visual disturbances (including refractive changes and diplopia), pseudopemphigoid, impairment of tear production and turnover, and choroidal detachment following filtration surgery have also been reported. In addition, cases of bacterial keratitis have been reported as a result of inadvertent contamination by patients.

The results of a comparative trial suggest that timolol maleate may be more irritating than timolol hemihydrate.

Blurred vision upon instillation lasting from 30 seconds to 5 minutes has been reported in 33% of patients receiving the sustained release gel forming solution.


Cardiovascular side effects have included bradycardia, arrhythmia, hypotension, hypertension, syncope, heart block, cerebral vascular accident, cerebral ischemia, exacerbation of angina, palpitation, cardiac arrest, pulmonary edema, edema, claudication, Raynaud's phenomenon, and cold hands and feet. It should be noted that death due to cardiac failure has been reported following use of ophthalmic timolol.

Cardiovascular side effects associated with oral timolol or other oral beta-blockers have included worsening of arterial insufficiency and vasodilatation.


Respiratory side effects have included respiratory failure, dyspnea, nasal congestion, cough, and upper respiratory infections. It should be noted that death due to bronchospasm, in patients with asthma, has been reported following use of ophthalmic timolol.

Respiratory side effects associated with timolol, as with other beta-antagonists, have included bronchial constriction in susceptible patients. Alternative therapy should be considered in patients with reactive airways disease.

Respiratory side effects associated with oral timolol or other oral beta-blockers have included rales and bronchial obstruction.

A case of refractory rhinitis is reported. The rhinitis may have been due to timolol-induced vasomotor changes.

The results of one study show that in otherwise healthy patients with glaucoma, long-term (3 yrs) treatment with ophthalmic timolol 0.5% can result in a significant reduction from baseline in FEV1 and a subclinical increase in bronchial reactivity which may not be completely reversible upon discontinuation of therapy.


Alternative therapy should be considered in patients with diabetes mellitus who are prone to hypoglycemia.

Endocrinologic side effects have included masking the signs and symptoms and blunting the normal physiologic response to hypoglycemia.

Endocrinologic side effects associated with timolol have included an increase in serum triglycerides, LDL cholesterol, and VLDL cholesterol, a decrease in HDL cholesterol, hyperglycemia, and hypoglycemia.

Nervous system

A case of amaurosis fugax is associated with timolol. However, the patient involved had underlying cerebrovascular disease, autonomic dysfunction, and an arrhythmia.

Nervous system side effects have included dizziness, headache, paresthesia, anxiety, somnolence, insomnia, nightmares, nervousness, memory loss, and disorientation. Timolol may worsen myasthenia gravis.

Nervous system side effects associated with oral timolol or other oral beta-blockers have included vertigo, local weakness, diminished concentration, an acute reversible syndrome characterized by disorientation for time and place, and slightly clouded sensorium.


Sexual dysfunction is reported from questionnaires, although the questions may have biased the data since the responses were not spontaneous.

Psychiatric side effects such as depression, confusion, hallucinations, and psychosis have been reported in rare cases. These effects may occur suddenly and are typically reversible upon discontinuation.

Psychiatric side effects associated with oral timolol or other oral beta-blockers have included reversible mental depression progressing to catatonia, emotional lability, and decreased performance on neuropsychometrics.


Dermatologic side effects have included contact dermatitis, urticaria and alopecia. Rare cases of psoriasis, prurigo and hyperpigmented nail beds have been reported.

Dermatologic side effects associated with oral timolol or other oral beta-blockers have included pruritus, skin irritation, and increased pigmentation.


Gastrointestinal side effects have included nausea, vomiting, diarrhea, dyspepsia, anorexia, and dry mouth.

Gastrointestinal side effects associated with oral timolol or other oral beta-blockers have included gastrointestinal pain, hepatomegaly, vomiting, mesenteric arterial thrombosis, and ischemic colitis.


An 86-year-old male with a 10 year history of chronic open angle glaucoma developed fever, malaise, pleurisy and recurrent sterile pleural effusions while taking only topical ophthalmic timolol. Antinuclear antibodies were present and the patient was felt to have timolol induced systemic lupus erythematosus. The patient improved upon the discontinuation of timolol and was not rechallenged.

Immunologic side effects have rarely included systemic lupus erythematosus and arthropathies.


Hypersensitivity reactions have included allergic conjunctivitis, anaphylaxis, angioedema, urticaria, and localized/generalized rash.

Hypersensitivity side effects associated with oral timolol and other oral beta-blockers have included erythematous rash, fever combined with aching and sore throat, and laryngospasm with respiratory distress.


Genitourinary side effects have rarely included complaints of impotence, retroperitoneal fibrosis, decreased libido, and Peyronie's disease.

Genitourinary side effects associated with oral timolol or other oral beta-blockers have included urination difficulties.


Other side effects have included asthenia/fatigue, chest pain, and tinnitus.

Other side effects associated with oral timolol or other oral beta-blockers have included extremity pain, decreased exercise tolerance, sweating, and weight loss.


Hematologic side effects associated with oral timolol or other oral beta-blockers have included nonthrombocytopenic purpura, thrombocytopenic purpura, and agranulocytosis.


Musculoskeletal side effects associated with oral timolol or other oral beta blockers have included arthralgia.

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