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PubMed1984

Effect of topical timolol maleate on exercise performance.

The effect of topical timolol maleate on exercise performance was investigated in a randomized double-blind study. Healthy young subjects underwent two graded maximal exercise evaluations on a treadmill. The evaluations were given one week apart. Before each trial, the subjects were given a single drop of either placebo or 0.5% timolol maleate in each eye. The results indicate that topical timolol has a statistically significant effect on both maximal heart rate and time to exhaustion. However, we found that the drug had no effect on the physiologic parameters of Vo2, respiratory rate, Vco2, or respiratory quotient.

Administration, Topical↗

PubMed1985

Clinical experience with timolol in childhood glaucoma.

We studied 67 patients (100 eyes) with childhood glaucoma who were treated with timolol maleate. Thirty of these patients (40 eyes) did not require additional surgery or medications after being treated with timolol (follow-up, from six to 60 months). Thirty-one eyes (78%) in this group had a pressure drop; 18 eyes (45%) had a pressure drop of greater than 10 mm Hg. We conclude that timolol is effective in the treatment of pediatric glaucoma, although there is a need to be aware of its potential complications.

Adolescent↗

PubMed1987

Intraocular pressure changes after neodymium-YAG laser capsulotomy in eyes pretreated with timolol.

Sixty eyes undergoing Q-switched neodymium-YAG laser posterior capsulotomy were randomly assigned to pretreatment with either 0.5% timolol maleate or placebo. Half of the eyes in each group underwent capsulotomies performed with six 2-mJ bursts of energy, and the remaining eyes underwent capsulotomies performed with three 4-mJ bursts of energy. There was no significant difference in pressure responses between eyes treated with 2 or 4 mJ. The mean rise in intraocular pressure was significantly less in the timolol-pretreated group one hour after capsulotomy. After four hours, the difference between groups was not significant. Pretreating with timolol did not prevent late pressure rises. Nonpseudophakic eyes were more likely to sustain pressure increases greater than 10 mm than were pseudophakic eyes.

Humans↗

PubMed1988

Topical beta-blocker therapy and central nervous system side effects. A preliminary study comparing betaxolol and timolol.

Topical beta-blocking agents have been associated with adverse central nervous system (CNS) effects, including depression, emotional lability, and sexual dysfunction. Two studies were done to determine if patients who develop CNS effects while using timolol maleate would improve with betaxolol hydrochloride. In one study, 18 patients with CNS symptoms during timolol therapy were switched to betaxolol. Sixteen of the 18 patients noted symptomatic improvement with betaxolol. The second study involved seven patients with CNS symptoms during timolol therapy who were entered into a double-masked cross-over study. In two patients CNS symptoms resolved with betaxolol; in three patients symptoms improved; and in one patient symptoms worsened with betaxolol. Although factors influencing beta-blocker activity in the CNS are not well understood, there may be some advantage to a selective agent.

Administration, Topical↗

PubMed1996

Around-the-clock intraocular pressure reduction with once-daily application of latanoprost by itself or in combination with timolol.

OBJECTIVE: To determine whether once-daily, in the morning, topical application of the new ocular hypotensive prostaglandin analogue, latanoprost, yields nocturnal intraocular pressure (IOP) reduction similar to its diurnal IOP reducing efficacy. STUDY DESIGN AND PATIENTS: Placebo- controlled, randomized, and double-masked study on hospitalized patients with ocular hypertension or glaucoma. Patients in group 1 (n=9) were maintained on twice-daily applications of 0.5% timolol maleate. Patients in group 2 (n=10) terminated their timolol treatment 3 weeks before the beginning of the study. In both groups the test drug (0.005% latanoprost) and its vehicle (placebo) was applied by hospital staff every morning for 9 days. MEASUREMENTS: After 4 days of ambulatory treatment, patients were hospitalized, and IOP values were obtained in the supine and sitting positions with a handheld electronic tonometer (Tono-Pen XL, Bio-Rad, Glendale, Calif) and a Goldmann's applanation tonometer, covering every 2-hour interval, around the clock, but not more than at four time points per day during a 5-day period. RESULTS: The mean nocturnal IOPs (Goldmann's applanation tonometer) collected for 5 days were mean +/-SEM 17.9+/-0.6 vs 20.2+/-0.6 mm Hg and 16.8+/-0.3 vs 20.6+/-0.5 mm Hg for the study vs the control eyes in group 1 and group 2, respectively. These nocturnal IOP reductions were statistically significant (P<.001, two-tailed paired Student's t test). The differences between diurnal and nocturnal IOP reductions (handheld electronic or Goldmann's applanation tonometer) were minimal (>0.3 mm Hg) and statistically not significant (P>.31, two-tailed paired Student's t test). CONCLUSION: Once-daily latanoprost treatment provides uniform circadian (around-the-clock) IOP reduction by itself, or in combination with timolol.

Adrenergic beta-Antagonists↗

PubMed2006

Pharmacokinetics of timolol in aqueous humor sampled by microdialysis after topical administration of thermosetting gels.

In order to develop a thermosetting gel-based formulation, the ocular pharmacokinetics of timolol was studied utilizing microdialysis sampling technique after topical administration. A linear microdialysis probe was characterized and implanted in the anterior chamber of a rabbit. Dialysate samples collected from the aqueous humor (AH) were directly injected into the HPLC system without any pre-treatment and no interference was observed in the blank sample. The measured in vitro recovery of the probe was 57.67%; however, the in vivo recovery significantly decreased to 16.78% when assessed by the retrodialysis method, which was used to calculate the timolol concentration in AH. Although in the initial 15 min the drug concentrations in AH were comparable to that of the timolol solution, increased Cmax and significantly improved ocular bioavailability were obtained for the gel. When sodium deoxycholate (DC) was incorporated in the gel as a penetration enhancer, a 2-fold increment in the ocular bioavailability was achieved with an increased Cmax and significantly suspended Tmax. The results demonstrated that microdialysis coupled to HPLC is a powerful tool to investigate the ocular pharmacokinetic, and hence facilitates the design of ophthalmic formulations.

Administration, Topical↗

PubMed1979

Hemodynamic effects of intravenous timolol in coronary artery disease.

The hemodynamic effects of intravenous timolol were evaluated in 20 patients with coronary artery disease during diagnostic cardiac catheterization. The threshold dose of 0.25 mg reduced heart rate and cardiac index by 15% (p less than 0.05), left ventricular work index by 21% (p less than 0.05), and left ventricular dp/dt by 16% (p less than 0.05) while increasing left ventricular end-diastolic pressure by 49% (p less than 0.01), mean pulmonary arterial pressure by 17% (p less than 0.01), and systemic vascular resistance by 16% (NS). Larger doses (0.5 mg and 1.0 mg) induced similar responses with a greater effect on systemic vascular resistance (+22%, p less than 0.01, and +31%, p less than 0.001). The mean arterial pressure and stroke volumes were not affected by timolol. Peak effects, occurring at about 10 min after drug injection, did not correlate with plasma levels. The overall hemodynamic effects of timolol were similar to those reported for equipotent doses of propranolol and could be accounted for by the beta-adrenoceptor blocking activity.

Adult↗

PubMed1981

Mass fragmentographic determination of timolol in human plasma and urine.

A mass fragmentographic procedure was developed for measuring quantities of less than 1.0 ng of timolol/ml of plasma or urine. The lower limit of sensitivity was 0.5 ng of timolol maleate/ml of plasma. The unchanged drug was extracted into heptane--4% isopentyl alcohol from alkalinized plasma or urine, together with propranolol hydrochloride as the internal standard. The compounds were subsequently back-extracted into 0.1 N HCl and then into chloroform following adjustment of the acidic phase to an alkaline pH. The chloroform layer was evaporated to dryness, and the compounds were derivatized with N-methyl-N-trimethylsilyltrifluoroacetamide-acetonitrile to form the trimethylsilyl derivatives; these derivatives were quantitated by mass fragmentography. Recovery of timolol added to normal plasma and urine was quantitative and reproducible, and no interfering substances were observed in normal biological samples. After a 20-mg oral dose of timolol maleate, plasma levels of approximately 3.0 ng/ml were observed at 12 hr.

Female↗

PubMed1991

A random walk method for percutaneous drug absorption pharmacokinetics: application to repeated administration of a therapeutic timolol patch.

A random walk method for predicting percutaneous drug absorption pharmacokinetics was proposed. The profiles predicted by this method were compatible with those predicted by the analytical method. The random walk method is particularly useful for predicting complex processes such as repeated topical application of a drug. The amount of a drug released into skin from four therapeutic timolol patches was measured when the patches were serially applied for 2.5 h each on the same site of six healthy male volunteers. On the average, 33.2, 23.4, 15.1, and 16.5% of the applied dose was released into skin from the first, second, third, and fourth patches, respectively. This pattern was comparable with the predicted profiles (43.9, 30.2, 24.4, and 21.1%) of amounts of drug which were expected to be released from the first to fourth patches into skin, respectively. The estimation method for the normalized skin-capillary boundary clearance is also described and applied in examining the percutaneous absorption of timolol. The estimated value for this parameter was much greater than the diffusion parameter, indicating that the removal process of timolol by the local circulation is much faster than the diffusion process through skin.

Administration, Cutaneous↗

PubMed1984

Effects of pilocarpine, timolol, epifrin and thymoxamine on iris vessels in rhesus monkeys.

In 24 normal eyes of healthy adult rhesus monkeys, the effects of 1% Pilocarpine, 0.5% Timolol, 0.5% levo-epinephrine (Epifrin) and 0.5% Thymoxamine were tested on the iris vessels, intraocular pressure and pupil size. Fluorescein iris angiography and applanation tonometry were performed on the eyes before the use of any drug, and then 2-4 h after topical instillation of each drug; all drugs were used in all the eyes, an interval of one week being left after the use of each drug. The findings of this study suggest that Pilocarpine and Timolol produced vasodilation. Epifrin and Thymoxamine seemed to have no appreciable effect. Pilocarpine produced miosis while other drugs had no significant effect on pupil size. Pilocarpine, Timolol and Epifrin each produced a significant fall in the intraocular pressure. The mechanisms of vascular changes are discussed. The various limitations of fluorescein iris angiography in such a study are stressed.

Animals↗

PubMed1978

Comparison of disposition and effect of timolol and propranolol on exercise tachycardia.

The kinetic disposition and beta-adrenergic blocking action in relation to plasma level of a single oral dose of either timolol or propranolol has been compared in healthy male volunteers. The disposition profiles clearly disclosed different properties of the two drugs, although their half-lives were similar. The available fraction of timolol in the systemic circulation was estimated to be approximately 60% of the dose, and 17.4% was exereted unchanged in urine. The logarithm of plasma concentration showed a significant correlation with the beta-blocking activity assessed by an exercise test. The mean potency ratios of timolol to propranolol as an antagonist of chronotropic effects on exercise tachycardia were 11 to 17 and 3.6 to 5.5 in dose- and concentration-effect relationships, respectively. The absolute reduction of exercise heart rate gave the best coefficient of all measures of beta-blockade. When drug action was measured as beta-blockade assessed by a given response to exercise tachycardia, the effect declined linearly with time, even though plasma levels fell exponentially. This results suggest that the pharmacokinetic t1/2 is much shorter than the pharmacological t1/2.

Adrenergic beta-Antagonists↗

PubMed1981

Pharmacokinetics of oral timolol studied by mass fragmentography.

The pharmacokinetics of timolol, after oral administration of single 20 mg doses to healthy subjects, has been studied using an original electron beam ionization GLC-mass spectrometry technique with computer -- controlled multiple ion detection. This method of mass fragmentography, tested with propranolol as an internal standard, permitted the measurement of timolol concentrations as low as 1 ng/ml with good precision and accuracy. It enabled the plasma level to be followed up to the twelfth hour after treatment. Individual variation was observed in bioavailability; the peaks plasma concentration (Cmax) of 50 to 103 ng/ml being achieved at different times(0.5--3h). The residual level after 12 h differed greatly between the subjects (0.8 to 7.2 ng/ml). The mean half-life of the terminal elimination phase was 2.62 +/- 0.17 h. Extra-renal elimination (metabolic and biliary) represented the main route of elimination, with a renal to body clearance ratio of 0.123. This level paralleled the percentage of unaltered timolol excreted in urine 24 h after its administration.

Administration, Oral↗

PubMed1979

[Timolol and acetazolamide in the treatment of increased intraocular pressure (author's transl)].

Twenty-four patients with open-angle glaucoma were tested to see if, and to what extent, timolol and acetazolamide produced a supplementary reduction of intraocular pressure. Twelve patients were treated with timolol eye drops, 0.5% b.d over a period of one week and then received one dose i.v. acetazolamide 250 mg which produced a statistically significant drop in intraocular pressure. Twelve patients with open-angle glaucoma who had been treated with acetazolamide 500 mg t.d.s. orally over a period of one week, received one drop of timolol 0.25% which produced a statistically significant additional effect. These results are discussed on the basis of the mode of action of the applied medications.

Acetazolamide↗

PubMed1983

Pharmacokinetic interactions of timolol with vasodilating drugs, food and phenobarbitone in healthy human volunteers.

Pharmacokinetic interactions of oral timolol maleate 10 mg, with food (3566 kJ), single oral doses of prazosin 1 mg and dihydralazine 25 mg, and with a 1 week pretreatment with phenobarbitone 100 mg daily were examined in a randomized crossover study in 12 healthy volunteers. After fasting, the peak level (Cmax = 29.1 +/- 3.2 ng/ml; mean +/- SEM) was reached at 1.3 +/- 0.1 h (Tmax). The total area under the serum concentration-time curve (AUC0-infinity) was 154.4 +/- 33.8 ng x h/ml, total clearance (Cltot) 751.5 +/- 90.6 ml/min, renal clearance (Clren) 97.2 +/- 10.1 ml/min, elimination half-life (t1/2) 2.9 +/- 0.3 h and 24-h recovery in urine (X0u-24) 11.1 +/- 1.4% of the dose. Food and prazosin did not significantly affect the fate of timolol maleate. Dihydralazine enhanced Cmax (38.2 +/- 4.6 ng/ml) only when compared to phenobarbitone treatment, and did not affect any other parameters. Phenobarbitone pretreatment somewhat lowered Cmax (25.5 +/- 3.9 ng/ml), AUC0-infinity (117.5 +/- 22.1; p less than 0.05 vs food) and X0u-24 (8.7 +/- 1.2%), evidently by increasing Cltot (957.5 +/- 116.9 ml/min; p less than 0.05 vs food), but it did not affect Clren. It is concluded that the pharmacokinetics of timolol maleate can be altered to a limited extent in opposite directions by dihydralazine and phenobarbitone.

Adult↗

PubMed1993

Topical timolol maleate might adversely affect serum lipoproteins.

Conflicting observations have been reported about the effects of topically administered timolol maleate on serum lipoproteins. We therefore considered this issue in a series of eight glaucoma patients receiving timolol maleate. Cholesterol and triglycerides were measured in plasma and in low-density lipoproteins (LDL), and high-density lipoproteins (HDL), both before and following three months of treatment. Following the treatment, the mean atherogenic index was increased from 2.72 to 3.38 (p = 0.012). This suggests that the atherogenic index should be determined before and during timolol maleate treatment in high-risk cardiovascular patients.

Administration, Topical↗

PubMed2001

Ocular surface changes induced by topical application of latanoprost and timolol: a short-term study in glaucomatous patients with and without allergic conjunctivitis.

BACKGROUND: This study evaluated the conjunctival effects of latanoprost and timolol, both of which contain benzalkonium chloride, in patients with primary open-angle glaucoma (POAG), with and without a history of allergic conjunctivitis (AC). METHODS: Two groups of 25 patients with and without a positive history for AC were studied. After a 21-day wash-out period patients were randomized to 14 days treatment with latanoprost or with timolol, in a cross-over fashion. The following parameters were evaluated on days 0 and 14: number of white blood cells, ferning test, conjunctival impression cytology, subjective symptoms, and objective ocular changes. RESULTS: Latanoprost caused: (a) an increase in eosinophils in both groups and reduction in lymphocytes only in the group with a history of AC; (b) alterations in ferning test and impression cytology only in AC patients; and (c) development of subjective symptoms and objective signs only in non-AC glaucomatous subjects. Timolol therapy was responsible only for the occurrence of subjective symptoms and objective signs in non-AC patients. CONCLUSION: Latanoprost treatment induces ocular surface changes which are more evident in POAG patients who are also affected by AC. These findings are probably related to the very high latanoprost concentration of benzalkonium chloride and to its bedtime administration, which further amplifies the toxicity.

Administration, Topical↗

PubMed1983

Maternal and fetal cardiovascular indices during fetal hypoxia due to cord compression in chronically cannulated sheep. I. Responses to timolol.

Timolol, one of the newer beta-adrenergic antagonists, has less depressive effects on the heart than propranolol, so that it has the potential for use by pregnant women. In chronically cannulated ewes, timolol at 0.01 and 0.1 mg/kg of body weight induced maternal and fetal bradycardia; the higher dose also depressed uterine blood flow and fetal PaO2. When this higher dose preceded brief compression of the umbilical cord, uterine flow was further depressed and the usual posthypoxia rebound tachycardia did not develop. Both the blocking of fetal responses to hypoxia (precluding detection of fetal distress) and the reduction in uterine flow led us to conclude that timolol taken by a mother could pose particular hazards for her fetus in hypoxic conditions, such as during cord compression at parturition.

Animals↗

PubMed1978

Clinical trial comparing timolol ophthalmic solution to pilocarpine in open-angle glaucoma.

A ten-week, double-masked, randomized, clinical trial compared timolol ophthalmic solution and pilocarpine in the therapy of open-angle glaucoma. Timolol decreased the intraocular pressure at least as much as pilocarpine and did not induce miosis, accommodative spasm, or other annoying side effects. The pulse was slowed by timolol, but blood pressure was unaffected. Significant decreases in intraocular pressure were still present after ten weeks of maintenance therapy with the same concentration of drug.

Adult↗