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PubMed1988

Prolonged aqueous humor levels of subconjunctival antibiotics after treatment with acetazolamide and/or timolol.

Many ophthalmologists routinely administer subconjunctival antibiotics at the end of cataract surgery for prophylaxis against bacterial endophthalmitis. Additionally they use acetazolamide and/or timolol to control intraocular pressure in the first 24-hour postoperative period. An animal study was undertaken to learn whether treatment with the aqueous humor suppressants, acetazolamide, and timolol prolongs the concentrations of antibiotics in the aqueous humor after subconjunctival administration of the antibiotic. Treatment with acetazolamide significantly increased concentrations of piperacillin; it had less consistent effects on tobramycin levels. Timolol treatment did not produce increased piperacillin concentrations at six hours; however, concentrations at 12 and 24 hours were significantly higher than in the controls. Timolol treatment increased tobramycin concentrations only at six hours. The combined use of timolol and acetazolamide produced significantly higher concentrations of piperacillin, but not of tobramycin.

Acetazolamide↗

PubMed1986

The effects of timolol on the active transport across the ciliary epithelium.

The mean transepithelial potential was +4.04 mV (cameral side positive to stroma). The results (Fig. 1) show that the short-circuit current was significantly reduced by timolol at 10(-4) and 10(-2) M (p less than 0.01). Since the short-circuit current across the isolated ciliary epithelium is a measure of active sodium transport in the direction stroma----posterior chamber there is an appreciable fall in Na +/- transport across the ciliary epithelium at a timolol concentration of 10(-4) M. On current values of aqueous humour secretion there would be a corresponding fall in aqueous production. For comparison it is worth recalling that the concentration of timolol in 0.5 per cent eye drops is slightly over 10(-2) M. Exposure of the tissue to timolol, a beta blocker does not seem to affect the subsequent response of the system to isoprenaline, a beta stimulant. A significant stimulation of short circuit current in the dose-range of 10(-4) to 10(-3) M with isoprenaline in a similar preparation was reported by Cole and Nagasubramanian and increase of short-circuit current and/or sodium transport in amphibian epithelia have been reported for catecholamines, and this effect may possibly be due to a decrease of the resistance to ions actively transported by the 'sodium pump' mechanism brought about via cyclic-AMP mediating the action at a cellular level. It appears that timolol has a direct effect on the active transport per se and by reducing the active ion influx can cause a reduction in the volume of aqueous production.

Animals↗

PubMed1978

[Experiences with timolol in treatment of glaucoma (author's transl)].

Timolol is a beta-adrenergic blocking agent that produces a significant decrease in intraocular pressure. Timolol ophthalmic solution 0,25% and 0,5% was compared to pilocarpine 1%, 2% and 4% in a randomized, double-masked study involving 40 patients with primary open angle glaucoma or ocular hypertension. Each patient was followed for 6 months. Timolol lowered the 1OP 30% compared to the pretreatment pressure, Pilocarpine 20%. Timolol was well tolerated in general, but 3 patients showed a superficial keratopathy. 30 other glaucoma patients with previously unsufficient pressure control received Timolol alone or in combination with a topical cholinergic agent or/and a systematic carbonic anhydrase inhibitor. The results are presented in detail.

Chemical Phenomena↗

PubMed1984

Migraine prevention with timolol. A double-blind crossover study.

One hundred seven patients (77 women and 30 men) with migraine headache were given prophylactic treatment with timolol maleate, 20 to 30 mg/day, or matching placebo during a 20-week, double-blind crossover study. Among the 94 patients who completed the study, timolol was significantly better than placebo in terms of decrease in frequency of headaches from baseline, numbers of patients who had a 50% reduction in headache frequency, global response, and patient preference. Overall global response rates were 65% with timolol compared with 40% with placebo. The severity and duration of headaches that occurred were unchanged. Few side effects were reported with either timolol or placebo. The study demonstrates that the beta-blocker timolol is a safe and effective treatment in patients with frequent migraine headaches.

Adolescent↗

PubMed1983

A comparison of timolol plus hydrochlorothiazide plus amiloride and methyldopa in essential hypertension in Black Africans.

The antihypertensive effect of the fixed combination of timolol, a beta-blocking agent, hydrochlorothiazide, a thiazide diuretic, and amiloride, a potassium sparing agent, was compared against that of methyldopa in an open study lasting 16 weeks in 32 ambulatory African patients with previously untreated diastolic blood pressure of 95-120 mm Hg. A significant fall in mean diastolic and systolic blood pressure was achieved in both groups up to 8 weeks of treatment and was sustained in the timolol-hydrochlorothiazide-amiloride group during the entire follow-up. In the methyldopa group, mean diastolic and systolic blood pressure rose during follow-up. At 16 weeks the fall in mean diastolic and systolic blood pressure was significantly greater in the timolol-hydrochlorothiazide-amiloride treated patients than in the methyldopa group. Adverse reactions were more frequent and severe in the methyldopa group than in timolol-hydrochlorothiazide-amiloride treated patients. It is concluded that the fixed drug combination of timolol-hydrochlorothiazide-amiloride (Moducren) is effective in controlling mild to moderate hypertension in Africans and is better tolerated than methyldopa in these patients. It is further noted that hypertensive patients can be treated with a combination tablet once a day. This is of crucial significance as it would promote better compliance and, hence, minimize the sequelae of poorly controlled hypertension.

Adult↗

PubMed1982

[Na+ and K+ in the rabbit aqueous humor after treatment with timolol].

The influence of timolol on aqueous humour production has been well documented, nevertheless it is unknown the real mechanism by which timolol produces this process. We have conceived the hypothesis that any alteration of natrium and kalium content following topical treatment of timolol was the main cause of the lowering rate of aqueous humour production. Therefore, we have examined the behaviour of Na+ and K+ amounts after topical administration of one eye of young rabbits with timolol. The experimentation has been conducted by photometer appliance. Our results show the absence of any imbalance between natrium and kalium content. The failure of our purpose indicates that Na+/K+ content does not play a main role in decreasing aqueous humour production by timolol.

Administration, Topical↗

PubMed1995

[Effect of topical timolol on the blood velocity of the iris microcirculation and the aqueous veins in human subjects].

To clarify the effect of topical timolol on the microcirculation in human eyes, the blood velocity changes of the iris microcirculation and the aqueous veins were measured before and 90 minutes after instillation of timolol in 8 eyes of 8 healthy volunteers by laser speckle flowgraphy. Systemic blood pressure, heart rate and intraocular pressure were measured before and 90 minutes after the instillation. The fellow eyes were measured as controls. The blood velocity decreased in the iris microcirculation (10% decrease, p < .05) and in the aqueous veins (8% decrease, p < .02) 90 minutes after instillation of timolol. The diameter of the aqueous veins did not change, so that the blood flow in the aqueous veins decreased (6% decrease, p < .02) after instillation. The intraocular pressure and pulse rate decreased (20 and 8% decrease, p < .002 and < .001, respectively) 90 minutes after the instillation. The blood velocity, vessel diameter, and intraocular pressure of fellow eyes and systemic blood pressure showed no significant change. These findings indicate that topical instillation of timolol induces decrease of blood flow in the iris, and, possibly, in the ciliary body. The instillation of timolol may decrease aqueous humor formation, and blood flow in aqueous veins.

Administration, Topical↗

PubMed1994

Ocular timolol levels after drug withdrawal: an experimental model.

Carbon 14-labelled timolol maleate was instilled into both eyes of 12 pigmented rabbits daily for 42 days. Drug levels in the aqueous humour and ocular tissues were measured up to 42 days after drug withdrawal. The results indicate that timolol concentrates mainly in melanotic tissues, with slow release. Even 42 days after withdrawal the drug was still present in pigmented ocular tissues. Timolol was detected in the aqueous up to 5 days after withdrawal. These findings explain the long-term depressant effect of topically administered timolol on aqueous production. We conclude that lower or less frequent doses of timolol should be considered in patients with glaucoma.

Animals↗

PubMed1994

The effect of topical timolol on epinephrine-stimulated aqueous humor flow in sleeping humans.

PURPOSE: It has been shown that intravenously administered epinephrine can increase the rate of aqueous humor flow in sleeping humans. This experiment was conducted to determine if this stimulatory effect can be blocked by the beta-adrenergic antagonist timolol. METHODS: Twenty normal human subjects were studied for one sleep cycle at night. Epinephrine was infused intravenously at a rate of 1 microgram/min. One eye received a single drop of 0.25% timolol, and the fellow eye received a placebo. Aqueous humor flow was measured by the rate of disappearance of fluorescein from the eye. RESULTS: The rate of aqueous humor flow was 14% lower in the timolol-treated eye than in the placebo-treated eye during 6 hours of sleep. This difference was interpreted as being due to blockage of part of epinephrine's effect on aqueous humor flow by topical timolol. CONCLUSION: It was concluded that the effect of systemically administered epinephrine on aqueous humor flow is at least partly mediated locally on the eye and that some portion of timolol's well-known effect on daytime aqueous humor flow could be due to inhibition of the ocular effects of epinephrine.

Administration, Topical↗

PubMed1993

A comparison of the ocular tolerability of a single dose of timolol and levobunolol in healthy normotensive volunteers.

Subject acceptance of a single dose of timolol and levobunolol was compared in a three-center, double-masked, randomized, crossover study in healthy normal subjects. We tested 115 subjects who received the medications OU, in a random order, separated by a washout period of three to seven days. At the end of the administration, the subjects were asked to report any symptoms and were monitored by ophthalmologic examination. Those receiving levobunolol reported a two- to threefold higher frequency of symptoms than did those receiving timolol (P = .0002, by Mainland-Gart chi-square test). Thirty-five subjects (30.4%) treated with levobunolol complained of burning versus 14 (12.2%) receiving timolol (P = .0021). Similar results were obtained in regard to stinging (31 versus 10 subjects; P = .0011). The duration of these symptoms did not differ between the two groups (P > .05). Timolol induced considerably less burning and stinging on day 1 compared with levobunolol, using a visual analog scale over time (P = .0004). Seventy-nine percent of those stating a preference chose timolol (P < 3 x 10(-9).

Adult↗

PubMed1996

The effects of the beta-adrenergic-blocking agents, timolol and carteolol, on plasma lipids and lipoproteins in Japanese glaucoma patients.

PURPOSE: To determine whether two topical beta-blockers, timolol and carteolol, differently affect plasma lipids and lipoproteins in normolipidemic Japanese patients with glaucoma. PATIENTS AND METHODS: Thirty-three normolipidemic patients with primary open-angle glaucoma or ocular hypertension were randomly allocated to and completed 16 weeks of bilateral treatment with 0.5% timolol, 1.0% carteolol, or 2.0% carteolol twice daily in a three-center, prospective study. Patients using any drugs affecting plasma lipids or with a history of beta-blocker use of hyperlipoproteinemia were excluded. Fasting blood lipids and lipoproteins, including total cholesterol, high-density lipoprotein cholesterol, triglyceride, and apoproteins, were measured three times before therapy was initiated. These measurements were repeated every 4 weeks during the treatment period. RESULTS: The level of high-density lipoprotein cholesterol significantly decreased in the timolol treatment group but did not change in the carteolol treatment groups. The ratio of total cholesterol minus high-density lipoprotein cholesterol to high-density lipoprotein cholesterol increased in the timolol treatment group. CONCLUSIONS: Topical beta-blockers do affect plasma lipids in Japanese patients with glaucoma. The effects of timolol are greater than those of carteolol.

Adrenergic beta-Antagonists↗

PubMed1997

Comparison of topical timolol gel to oral acetazolamide in the prophylaxis of viscoelastic-induced ocular hypertension after penetrating keratoplasty.

PURPOSE: Viscoelastic-induced ocular hypertension following penetrating keratoplasty (PK) may result in endothelial cell loss and optic nerve damage. METHODS: In a prospective, randomized, masked trial, two doses of oral sustained-release acetazolamide were compared to a single dose of topical 0.5% timolol gel after 40 PKs. RESULTS: The mean preoperative intraocular pressure (IOP) was 17.4 mm Hg for the oral acetazolamide group and 16.7 mm Hg for the timolol gel group. The mean IOP on the first postoperative day was 17.9 mm Hg with oral acetazolamide and 12.9 mm Hg with timolol gel. One patient developed significant adverse reactions with oral acetazolamide; there were no adverse reactions with timolol gel. CONCLUSION: Prophylactic use of timolol gel for viscoelastic-induced ocular hypertension after PK appears to offer better IOP control than oral acetazolamide, with potentially fewer adverse systemic effects.

Acetazolamide↗

PubMed1997

Timolol decreases aqueous humor flow but not Na+ movement from plasma to aqueous.

PURPOSE: To determine whether the well-known effect of timolol in reducing ocular pressure and aqueous humor (AH) flow is a function of reduced Na+ movement from plasma to aqueous. Previously, the authors have shown this to be the case for carbonic anhydrase inhibitors. METHODS: The rate of appearance of 22Na in rabbit posterior aqueous was measured 1 to 3 minutes after the intravenous injection (time T) of the isotope. One hour before this, the animals received one of the following: two drops of 0.5% timolol, two drops of 3.5% pilocarpine, or 25 mg/kg intravenous methazolamide. At 1 minute (T + 1), a posterior chamber sample was taken; 2 minutes later (T + 3) a second sample was removed from the fellow eye. The rate constant of sodium accession is simply the difference between the two counts/2 minutes. Aqueous flow was measured by dilution of sulfacetamide marker as described previously. RESULTS: The rate constant (k(in)) for sodium entering the posterior chamber was 0.036 +/- 0.004 minute-1 (n = 17). Corresponding to previous findings, methazolamide (25 mg/kg intravenous) reduced this to 0.023 +/- 0.003 minute-1 (n = 14). Conversely, timolol (two drops of 0.5% solution) had no effect on kin, which measured 0.037 +/- 0.004 minute-1 (n = 12). Similarly, as expected, pilocarpine had no effect on k(in) (0.035 +/- 0.003 minute-1). Control flow was 3.9 microliters/minute +/- 0.4; after timolol, 2.5 microliters/minute +/-0.1; after methazolamide, 2.4 microliters/minute +/-0.2; after pilocarpine, 3.6 microliters/minute +/- 0.2. These are converted to rate constants by dividing by volume of posterior aqueous (60 microliters). The control rate constant for fluid entry was 0.065 minute-1, 1.8-fold higher than for sodium. CONCLUSIONS: A central dogma of the formation of AH (and cerebrospinal fluid) is that fluid moves isotonically from plasma to AH or cerebrospinal fluid and, therefore, that rate constant k(in) for fluid and for sodium are approximately the same. In the authors' hands, the fluid constant was modestly higher than for sodium. This holds for normal function and also for the reduced k(in) for fluid and sodium after carbonic anhydrase inhibition. The k(in) for neither flow nor sodium was affected by pilocarpine. Surprisingly, however timolol, which reduces flow, had no effect on Na+ entry.

Adrenergic beta-Antagonists↗

PubMed1998

The effects of unoprostone isopropyl 0.12% and timolol maleate 0.5% on diurnal intraocular pressure.

PURPOSE: To compare the effect of unoprostone isopropyl 0.12% to that of timolol maleate 0.5% solution given twice daily on the diurnal curve of intraocular pressure (IOP) in patients with primary open-angle glaucoma or ocular hypertension. METHODS: In this investigator-masked, single-center, parallel-group comparison, 36 patients with primary open-angle glaucoma or ocular hypertension were randomized in a 2:1 ratio to receive either unoprostone isopropyl 0.12% or placebo/timolol maleate 0.5% solution, respectively. A placebo-controlled diurnal curve on day 0 and active-controlled diurnal curves at weeks 2 and 4 were performed at 0, 2, 4, 6, 8, 10, 12, and 24 hours. At week 2, administration of unoprostone isopropyl twice daily was compared with administration of timolol maleate twice daily. At week 4, administration of unoprostone isopropyl three times daily was compared with administration of timolol maleate twice daily. RESULTS: At the 24-hour 8:00 AM trough at week 2, administration of unoprostone isopropyl twice daily decreased IOP from 23.4 +/- 2.0 mmHg at baseline to 19.3 +/- 4.4 mmHg, and timolol maleate reduced IOP from 24.4 +/- 2.6 mmHg to 17.5 +/- 2.9 mmHg. At the 8:00 AM trough at week 4, unoprostone isopropyl given three times daily produced an IOP of 19.6 +/- 3.3 mmHg and timolol maleate resulted in an IOP of 19.4 +/- 3.0 mmHg. No statistical differences between groups were observed at any time point during either diurnal curve. Safety was similar in the two treatment groups, with no differences between groups in conjunctival hyperemia, anterior segment inflammation, or iris color change. CONCLUSION: Results of this short-term pilot trial indicate that unoprostone isopropyl may be safe and effective in reducing IOP from baseline when given twice or three times daily.

Circadian Rhythm↗

PubMed1975

Normal cardiac output during beta blockade with timolol in hypertensive patients.

Data published by this laboratory indicated that the beta adrenergic blocking drugs timolol and propranolol exerted equivalent beta blocking and antihypertensive actions in patients with mild essential hypertension, but that whereas cardiac output fell acutely with both drugs, it returned to normal after 5 wk of treatment with timolol, but remained depressed after propranolol. This preliminary observation needed further confirmation in a larger series of patients. In this study, 11 patients with initial diastolic blood pressures between 90 and 125 mm Hg were given timolol for 5 wk. Hemodynamic measurements were made before and at the end of treatment. Mean heart rate fell from 76.8 to 64.3 bpm (p less than 0.001), and blood pressure was reduced from 179.4/99 mm Hg to 167.4/93.3 mm Hg (less than 0.02). Cardiac output averaged 6.29 L/min before timolol, and fell to 5.95 L/min (NS) after treatment. Stroke volume increased significantly, while total peripheral resistance was unchanged. These results confirm our earlier observations that timolol is an effective beta adrenergic blocking drug with antihypertensive action that does not reduce cardiac output significantly when given chronically. This drug merits further evaluation in other cardiovascular disorders since it may have advantages over other beta adrenergic blocking drugs.

Adrenergic beta-Antagonists↗

PubMed1975

Comparison of cardiac effects of timolol and propranolol.

The cardiac effects of the beta-adrenergic blocking agent, timolol, were compared to those of propranolol after intravenous administration in 6 healthy male subjects. The effects of timolol and propranolol on maximal exercise-induced tachycardia were measured. Timolol was about ten times as potent as propranolol in antagonizing exercise-induced tachycardia. Dose-response curves to intravenous infusions of isoproterenol were obtained after three doses of each beta-antagonist. Changes in myocardial contractility were assessed by cardiac systolic time intervals and were compared to the simultaneous changes in heart rate elicited by isoproterenol. For the 6 subjects, the mean potency ratios of timolol to propranolol as an antagonist of the chronotropic and inotropic effects of isoproterenol were 13.8 (+/-0.8) and 12.7 (+/-1.0), respectively. Neither timolol nor propranolol acted more selectively on beta-receptors affecting heart rate than on those influencing contractility.

Adult↗

PubMed1975

A comparison of timolol and propranolol in essential hypertension.

The antihypertensive efficacy of a new beta-adrenergic receptor inhibiting compound, timolol (MK-950), was evaluated using two treatment protocols: double-blind timolol vs. placebo treatment and double-blind timolol vs. propranolol (10 and 12 patients, respectively). These studies indicate that timolol significantly and safely reduced arterial pressure in mild to moderately severe essential hypertensive patients. The reduction in mean arterial pressure with timolol was equivalent to the pressure reduction with propranolol when the doses of 30 and 120 mg. per day, respectively, were used.

Adrenergic beta-Antagonists↗

PubMed1976

Cardiovascular and beta-adrenergic blocking effects of timolol.

The haemodynamic effects of timolol and its inhibiting action on the cardiovascular and bronchial effects of isoproterenol have been studied. Splanchnic nerve activity was recorded. The antiarrhythmic action of timolol was studied on guinea pig isolated atria, using arrhythmias induced by epinephrine, ouabain or coronary ligation in the dog. Timolol is a very potent beta-adrenoceptor blocking agent, without specificity on beta1- or beta2-receptors. No intrinsic beta-stimulating or depressant effects were found. Timolol reduced splanchnic discharges. The antiarrhythmic effect of timolol was limited to epinephrine-induced arrhythmias.

Adrenergic beta-Antagonists↗