Synthesis and ocular antihypertensive activity of new imidazolidine derivatives containing a beta-blocking side chain.

The syntheses of new phenylimidazolidine derivatives (3-6)1 containing a propanolamine oxime or an oxypropanolamine moiety attached either to the aromatic or to the imidazolidine ring are described. These compounds were evaluated for potential ocular antihypertensive activity in alpha-chymotrypsin-induced ocular hypertension in rabbits. These compounds represent a unique series of effective ocular antihypertensive agents that despite possessing structural characteristics of beta-blockers and of imidazolidine derivatives, exhibit weak alpha- and beta-adrenergic agonist and antagonist activities. These findings may be of significant therapeutic importance in the medical management of glaucoma.

Pharmacokinetics of falintolol II. Absorption, distribution and elimination from tissues and organs following ocular administration and intravenous injection of falintolol in albino rabbits.

The absorption, distribution and elimination of falintolol maleate was studied in various ocular and extraocular tissues and organs following ocular instillation, intravenous injection of a 0.5% 14C-falintolol ophthalmic solution and repeated ocular instillations of a 1% non-labeled falintolol ophthalmic solution into albino New Zealand rabbits. Falintolol was distributed in all studied tissues and organs after both routes of administration. After ocular instillation, levels of total radioactivity were distinctly higher in ocular tissues than after intravenous injection. Thus, the level was 475 times more important in cornea, 72 times in aqueous humor and 36 times in iris and ciliary body after ocular instillation. On the other hand, levels of total radioactivity in extraocular tissues and organs were 30-50% higher after intravenous injection compared to ocular instillation of the same dose. Peak levels of total radioactivity were generally achieved between 30 min and 1 h after ocular instillation, while 1.5 h after intravenous injection an increase in the declining part of the curve occurred. This increase, characteristic of an enterohepatic reabsorption, was also observed in blood and plasma 1 h after intravenous injection. Urinary elimination was the major means of excretion since 79.6% of total radioactivity was found in urine 6 h after intravenous injection and 74.5% 12 h after ocular instillation. But after ocular instillation, only 5% was excreted as unchanged falintolol. Whatever the route of administration, after single or repeated application, no drug accumulation was evident.

Beta-adrenoceptor binding potencies of new aliphatic and alicyclic oxime ethers and their relevance to intraocular pressure control.

The selectivity and binding potency of a series of alkyliminoxypropanolamines characterized by the lack of an aromatic nucleus are studied using a new non-selective radioligand, (-)-(125I)-Iodocyanopindolol. The relationship between the effectiveness in lowering the intraocular pressure (IOP) in experimental hypertensive rabbit eyes and their capacity to bind to ciliary processes beta 2-adrenoceptors is discussed. The inhibition constant (Ki) and beta 2/beta 1 ratios indicate a beta 2-selectivity for the tested drugs. Cyclopropyl, dicyclopropyl, cyclopentyl and cyclohexyl derivatives displayed a potent binding to ciliary processes beta 2-adrenoceptors and lowered the IOP about -18%. These compounds induced a lowering in IOP equal to that produced by timolol and appear to be effective and safe beta-adrenergic antagonists in open-angle glaucoma therapy. Decreasing the size of the alkyl group of the oxime, removing the oxime function or modifying the beta-hydroxyl group from the side chain led to a significant decrease in beta 2-adrenoceptor binding and induced weak hypotensive ocular activity. Since the tested alkyliminoxypropanolamine series has very similar physicochemical characteristics and therefore, ruled out the differences in their ability to reach, through the cornea, the targeted ciliary processes, it was demonstrated that contrary to generally held views, the action of the new beta-antagonist series on IOP is related to their ability to antagonize ocular beta 2-adrenoceptors.

Effects of adrenergic agents on alpha-chymotrypsin-induced ocular hypertension in albino and pigmented rabbits: a comparative study.

Alpha-chymotrypsin-induced ocular hypertension in albino rabbits is widely used as an experimental model to screen potential antiglaucoma drugs. The present study compares the intraocular pressure (IOP) response following the ocular application of single or repeated adrenergic agents in conscious albino and pigmented rabbits. A single instillation of clonidine was not as effective in lowering the IOP in pigmented hypertensive rabbit eyes as in albino hypertensive eyes. Similarly, betaxolol moderately lowered the IOP in albino rabbits but induced a slight response when pigmented rabbits were used as an experimental model. Twice-a-day applications of betaxolol in pigmented hypertensive eyes permitted an identical level of IOP decrease to be reached, as observed in a one-day study in albino rabbits, after at least 6 days of treatment. It has been suggested that the pigmented layers of the iris-ciliary body may act as sites for topically applied antiglaucoma drugs. Non-specific binding could explain in part the frequent discrepancy observed between the preclinical results obtained in albino hypertensive rabbit eyes and clinical results obtained in glaucomatous human eyes.

Characterization of alpha 2-adrenergic receptors, negatively coupled to adenylate cyclase, in rabbit ciliary processes.

Inhibition of ciliary process adenylate cyclase was studied on rabbit membrane preparations. When considered individually, epinephrine, GTP and NaCl did not inhibit adenylate cyclase activity. On the other hand, when present together, epinephrine, GTP (10(-5) M) and NaCl (200 mM) acted synergistically to cause a 27% inhibition of basal activity. A similar inhibition was observed with 1-norepinephrine. Clonidine and BHT 920, two alpha 2-agents were found to be partial agonists causing 63% and 82% as much inhibition as epinephrine. Phenylephrine, an alpha 1-agonist did not inhibit adenylate cyclase activity at concentrations up to 10(-4) M. Yohimbine and phentolamine prevented the inhibition of adenylate cyclase by epinephrine, while prazosin was ineffective. Alpha 2-receptor selectivity in rabbit ciliary processes and their negative coupling to an adenylate cyclase via a NaCl-dependent GTP binding protein, Ni, is thus well established.

Effects of topically applied falintolol: a new beta-adrenergic antagonist for treatment of glaucoma.

Changes in intraocular pressure (IOP) following topical administration of falintolol (0.5%-0.25%), a new beta-blocking agent, were studied in conscious albino rabbits with alpha-chymotrypsin-induced ocular hypertension. The drug produced a reduction in IOP equal to that of timolol. A longer duration of activity was noted with falintolol. The rate of transport of topically applied falintolol through the isolated bovine cornea under conditions simulating normal physiology was linear up to three hours and twice as fast as timolol from 3 to 6 hours. Since topical ocular application of beta-adrenergic antagonists useful in glaucoma therapy can also cause a number of troublesome systemic side effects, several conclusive preclinical investigations were carried out with falintolol. Of major concern was the effect falintolol might have on the pupil, cornea, and heart rate when administered topically. The results show that falintolol does not produce any noteworthy side effects and is capable of being an effective beta-blocking agent in open-angle glaucoma therapy.

Determination of falintolol, a new aliphatic beta-adrenergic antagonist, in whole blood by gas chromatography with electron-capture detection: geometric isomers resolution.

Falintolol oxalate, a new beta-adrenergic antagonist, is characterized by the presence of an oxime function and exists in a racemic form as a mixture of syn- and anti- isomers in a ratio of about 8:2. This article describes a selective gas chromatographic method for the resolution of the geometric isomers and the quantitation of the drug. The unchanged falintolol and internal standard, a related compound, are separated from blood by a solvent extraction under alkaline conditions, and then the drug is derivatized. The heptafluorobutyric derivatives are chromatographed on an SE-30 capillary quartz column and detected with a nickel-63 electron-capture detector. Because the syn- and anti- isomers of falintolol display comparable chromatographic responses, the sum of the two geometrical isomers is used for the quantitation of falintolol in blood. This method allows small serial blood samples in conscious rats, and 0.05 microgram of falintolol/0.1 mL of blood can be routinely determined. A calibration curve is prepared for the blood extracts. Linearity is observed in the study range (0.05 to 1 microgram/0.1 mL of blood). No interference by endogenous substances is observed. The procedure is applied successfully to drug absorption in rats when repeated oral doses are administered.

New chiral and isomeric cyclopropyl ketoxime propanolamine derivatives with potent beta-adrenergic blocking properties.

The synthesis of R-(+) and S-(-) isomers of O-[3-tert-butylamino)-2-hydroxypropyl] cyclopropyl methyl ketone oxime (falintolol) is described. The syn and anti isomers of falintolol were obtained in two different ways from cyclopropyl methyl ketoxime or from falintolol. For comparison purposes, the enantiomers of the dicyclopropyl ketone oxime derivatives were also prepared. Structure-activity relationships are described.

In vitro potential measurement, anaesthetic and antimicrobial effects as indicators of beta-blocker toxicity of the cornea.

Three tests were utilized to determine and compare the toxicity of timolol, propranolol and two new aliphatic and alicyclic oxime ethers with beta-blocking activity (falintolol and compound POS 7). Effects on the electrical potential difference across the in vitro bovine corneal epithelium. Local anaesthesia on in vivo rabbit cornea. Antimicrobial activity on bacterial and fungal suspensions. In addition, partition coefficients were determined as physicochemical properties of the drugs. Falintolol, as well as timolol produced a minor change in electrophysiology at clinical concentration. They had neither local anaesthetic, nor antimicrobial effects. Conversely, propranolol and compound POS 7 showed acute corneal toxicity in the present models. It was concluded that changes in the potential difference across a perfused cornea in vitro, local anaesthesia and bacterial inhibition, might be a demonstration of the cytotoxicity of certain topical agents in terms of acute eye tissue reaction. They might represent a valuable model for the acute corneal toxicity evaluation of topical beta-blockers.

Topical and bioavailability of benzoyl peroxide.

Synopsis Benzoyl peroxide has been used for over 20 years to treat youthful acne. The aim of this study is to determine its release rate from the vehicle that allows it to reach and treat the skin (topical availability) and its ability to pass through the skin and reach the general circulation (bioavailability), in order to bring about good topical availability, linked to bioavailability or, an 'abioavailability'. Three preparations containing 10% of benzoyl peroxide were administered to the back of shaven New Zealand rabbits. At day 0, day 5, day 12, day 19, day 26 and day 33, the topical effects were measured by cutaneous temperature, degree of erythema and the benzoic acid plasma record card, which shows blood sample results of the metabolism of the drug. The results obtained show that the topical availability of benzoyl peroxide coincides with a decrease in cutaneous temperature, after application in various dosage forms, in spite of the appearance of a marked erythema. The bioavailability is demonstrated by plasma benzoic acid evaluation. Before administration, benzoic acid levels are low but increase half an hour after administration, to reach a maximal level at 3 h. Benzoyl peroxide metabolizes quickly and does not seem to be able to cross the skin without being changed.

Synthesis and beta-adrenergic blocking activity of new aliphatic and alicyclic oxime ethers.

We describe the synthesis and pharmacological properties of two new series of aliphatic and alicyclic beta-adrenergic blockers, most of them containing a cyclopropyl ring. They belong either to 2-hydroxy-3-(tert-butylamino)propyl ether A or 2-hydroxy-3-tert-(butylamino)propyl ketoxime ether B derivatives. The O-[2-hydroxy-3-(tert-butylamino)propyl] dicyclopropyl ketoxime 5 exhibited a beta-adrenergic antagonist activity comparable to that of propranolol. It was found that ketoxime ethers B generally showed higher potency than the corresponding ethers A. We confirm that the presence of an aromatic nucleus is not crucial for the beta-adrenergic activity. Structure-activity relationships among these series are discussed.

Simultaneous determination of neopynamine and piperonyl butoxide by capillary column gas-liquid chromatography.

A method is developed for the simultaneous determination of neopynamine and piperonyl butoxide by chromatography on a quartz capillary column using flame ionization detection. Benzyl mandelate is used as an internal standard. Calibration graphs are linear down to at least 3.75 mg% and 3 mg% for neopynamine and piperonyl butoxide, respectively.

[Demonstration of the effects on the corneal epithelium of a mucomimetic collyrium. Study using scanning microscopy]. / Mise en évidence des effets sur l'épithélium cornéen d'un collyre mucomimétique. Etude en microscopie à balayage.

Ocular surface drying was studied in rabbits using an experimental model of blinking interruption. This model produces a discontinuity in the pre-corneal tear film after a few minutes of exposure to air. Changes in superficial epithelial cell structure were studied using a scan microscope. A decrease of micro-folds and an increase in epithelial cell desquamation were observed. Prolonged exposure to air produced similar cellular lesions in deeper layers. The instillation of a single mucomimetic eye-drop containing chondroitin sulphate prevented total interruption of epithelial humidification, kept the epithelial surface intact and preserved normal cellular structure.