[The distribution of 2-(dimethylamino)ethyl-(1-hydroxycyclopentyl)(phenyl)acetate in the organism of the warm-blooded animals after its intra-gastric administration]

The objective of the present study was to elucidate the distribution of 2-(dimethylamino)ethyl-(1-hydroxycyclopentyl)(phenyl)acetate in the organism of the warm-blooded animals after its intra-gastric administration. The methods applied in the study included thin layer chromatography in silicagel, aci-nitroprosalt staining reaction, UV-spectrophotometry,, and GC-mass spectrometry. The identification and the quantitation of 2-(dimethylamino)ethyl-(1-hydroxycyclopentyl)(phenyl)acetate in the organs and blood of the warm-blooded animals were carried out within 20, 150, and 360 min after a single intra-gastric administration of 1300 ml of this poisonous substance. It was shown that the largest amounts of 2-(dimethylamino)ethyl-(1-hydrpxycyclopentyl)(phenyl)acetate at the above time-points were present in the tissue of the stomach and small intestine, brain, muscles, spleen, and lungs of the animals.

Anaphylactic reaction due to cyclopentolate in a 4-year-old child

Ophthalmologists frequently use mydriatics both for diagnosis (retinal exploration, refraction tests) and for treatment. Cyclopentolate is used to induce quick and successful mydriasis for pediatric eye examination. Hypersensitivity reaction to cyclopentolate is very uncommon, especially in children. We report the case of a child who experienced a hypersensitivity reaction to cyclopentolate during preparation for an eye examination under cycloplegia.

Ophthalmic vehicles containing polymer-solubilized tropicamide: "in vitro/in vivo" evaluation

Commercial 1.0% aqueous tropicamide (TR) eyedrops are buffered to pH 4.4-5.0 to produce sufficiently stable solutions of the weakly basic, poorly soluble drug. These acidic solutions, however, are irritants and may induce copious lachrimation, thus reducing the drug bioavailability. The aim of the present study was to evaluate some solubilizing agents for the preparation of 1.0% TR ophthalmic solutions adjusted at physiologically compatible pH, potentially showing increased eye tolerance, activity, and stability when compared with standard commercial eyedrops. The tested solubilizers were two non-ionic surfactants-Tyloxapol (TY) and Cremophor EL (CR) and one polymer, Pluronic P85 (PL). Four stable 1% TR formulations, containing 3% TY, 7.5% CR, 15% PL, or 5% CR + 10% PL were submitted to mydriatic activity tests in rabbits. They improved to a small but statistically significant extent the AUC for mydriatic effect of TR in the test animals when compared with commercial 1.0% TR eyedrops.

Locomotor stimulant effects of novel phenyltropanes in the mouse

With the hypothesis that 3-phenyltropane analogs of cocaine might be useful as cocaine medications, 17 analogs (RTI-51, RTI-55, RTI-108, RTI-112, RTI-113, RTI-116, RTI-120, RTI-121, RTI-126, RTI-139, RTI-141, RTI-150, RTI-171, RTI-177, RTI-199, RTI-204, and RTI-219) were characterized for their potency and selectivity at the monoamine transporters in a previous study. Based on their affinities to the transporters in this earlier study, the analogs were classified as nonselective (cocaine, RTI-51, RTI-55, RTI-108, RTI-112, RTI-116, RTI-126, and RTI-139) or dopamine transporter (DAT) selective (RTI-113, RTI-120, RTI-121, RTI-141, RTI-150, RTI-171, RTI-177, RTI-199, RTI-204, and RTI-219). In the present study, the locomotor stimulating effects of these analogs were compared to those of cocaine to obtain a measure of in vivo activity. Each analog was more potent than cocaine in the in vivo assay, as observed in the earlier in vitro studies. Most of these compounds were as efficacious as cocaine, but RTI-51, RTI-108, RTI-113, RTI-121, RTI-139, RTI-141, RTI-177, RTI-204, and RTI-219 were longer acting. Although no correlation between chemical structure and transporter selectivity was found, the short-acting DAT-selective analogs, RTI-120, RTI-150, RTI-171, and RTI-199, all contained a methyl group in the X position of the WIN 35,065-2 molecule. The positive correlation of the IC(50)s for the DAT to potencies for increasing locomotor activity suggested that binding to DAT was responsible for some, if not most, of the locomotor effects of these compounds. Several compounds, including RTI-113 and RTI-177, exhibited properties ideal for medications for cocaine abusers, such as an equivalent efficacy, a higher potency, and a longer duration of action as compared to cocaine.

Solubilization of tropicamide by hydroxypropyl-beta-cyclodextrin and water-soluble polymers: in vitro/in vivo studies

1% (w/v) aqueous solutions of tropicamide (TR), a poorly water-soluble mydriatic-cycloplegic drug, are usually obtained by adjusting the pH to approximately 5.0, at the expense, however, of ocular tolerance and bioavailability. The capacity of hydroxypropyl-beta-cyclodextrin (HP-beta-CD) to solubilize TR in pH 7.4 0.02 M phosphate buffer was investigated in the absence and presence of hydrophilic polymers (PVP, CMC and HPMC). Approximately 3.5% (w/v) HP-beta-CD was required to solubilize 1% (w/v) TR in pH 7.4 buffer at room temperature. The required amount was reduced to 0.9% (w/v) by heating at 120 degrees C in the presence of 0.1% (w/v) HPMC. Mydriatic activity tests in rabbits showed an improved bioavailability and maximal mydriatic response for two CD formulations, with and without HPMC, when compared to standard 1% (w/v) TR eyedrops, buffered at pH 5.0. The improved in vivo behaviour of the CD formulations are likely due to their physiological pH, resulting in a reduced irritant effect, although an effect of HP-beta-CD on corneal permeability cannot be dismissed a priori.

Chemical delivery systems: evaluation of physicochemical properties and enzymatic stability of phenylephrone derivatives

The physicochemical properties and enzymatic stability of esters of phenylephrone, synthesized on the basis of the chemical delivery system (CDS) concept, were studied as a new class of mydriatic agents. Potentiometrically determined ionization constants (pKa) of the novel compounds were in the range 7.19-7.21. The three esters of phenylephrone (isovaleryl, phenylacetyl, and pivalyl) were more lipophilic than phenylephrone as indicated by n-octanol/pH 7.4 buffer partition coefficients (log Papp) and the chromatographic capacity factors (log k'). The chemical stability of the esters of phenylephrone was evaluated in hydrochloric acid, citrate, and phosphate buffers (with pH ranging between 2.0 and 8.0), and the enzymatic hydrolysis in rat and human plasma. The samples were analyzed using HPLC assay procedures. The phenylephrone esters were found to undergo comparatively slow hydrolytic degradation in buffer with pH 3.0 and 4.0, with half-lives ranging from 1136 to 1980 hr at 37 degrees C. The novel esters were readily hydrolyzed in human plasma with half-lives ranging between 16.2 and 47.8 min. The hydrolytic degradation rates were higher in rat plasma than in human plasma, in which the half-lives were in the range of 9.8-38.3 min. In the present investigations, only phenylephrone, not the active species phenylephrine, was detected. Among the esters studied, isovaleryl ester was the most labile. Pivalyl ester, having a tertiary carbon, showed relatively high resistance to chemical and enzymatic hydrolysis because of the steric hindrance, followed by phenyl and isovaleryl esters. The results suggest that the duration of action of the phenylephrone CDS can be controlled with proper chemical manipulations.

Particle size and drug interactions of injectable corticosteroids used in ophthalmic practice

PURPOSE

The aim of this study is to compare the particle sizes of commercially available corticosteroids for intralesional injection to manufacturers' specifications and to evaluate changes in size when mixed with other steroids and other commonly used solutions.

METHODS

The particle sizes of dexamethasone sodium phosphate, methylprednisolone acetate, triamcinolone acetonide, and betamethasone sodium phosphate and beta-methasone acetate were measured with the Coulter counter. Each steroid was mixed with each of the others, lidocaine, and lidocaine with epinephrine, then measured immediately and after 1 hour to determine the effect on particle size.

RESULTS

All steroids showed accurate manufacturer specifications. Dexamethasone showed an increase in particle size when mixed with lidocaine alone, immediately and after 1 hour. Triamcinolone showed an increase in particle size only after 1 hour after mixture with lidocaine alone. Triamcinolone, dexamethasone, and methylprednisolone particles increased in size when mixed with lidocaine and epinephrine. Dexamethasone and triamcinolone showed an additional increase in size when allowed to sit for 1 hour after mixture with lidocaine and epinephrine. Mixing steroids caused no increase in particle size.

CONCLUSION

Because an increase in the number of particles greater than 20 microns in a solution also increases the likelihood of vascular occlusion, the authors urge care in the mixing of these drugs, especially with lidocaine and epinephrine. If mixture is necessary, the authors recommend that injection take place immediately subsequent.

A comparative study of the efficacy of 2.5% phenylephrine and 10% phenylephrine in pre-operative mydriasis for routine cataract surgery

It is common practice in many ophthalmic units to administer multiple applications of 10% phenylephrine in combination with an anti-cholinergic agent to ensure adequate pupil mydriasis prior to routine cataract surgery. Phenylephrine is a pure alpha-1 adrenoreceptor agonist known to produce marked systemic vasoconstriction and associated hypertension with occasional profound reflex bradycardia. Many reviews have suggested caution in the use of 10% phenylephrine in the elderly or hypertensive patient. In a prospective, randomised trial we have assessed pupil dilation comparing the efficacy of 10% phenylephrine (53 patients) versus 2.5% phenylephrine (62 patients). When administered in conjunction with 1% cyclopentolate four times over 1 hour pre-operatively, 2.5% phenylephrine was found to be as effective as 10% phenylephrine in the initiation and maintenance of mydriasis during both extracapsular and phacoemulsification cataract extraction.

Soft drugs--XIV. Synthesis and anticholinergic activity of soft phenylsuccinic analogs of methatropine

Three soft drug analogs and a metabolite of methatropine based on phenylsuccinic structural moiety were synthesized and tested for activity. In an in vivo assay, the soft drugs were found to be two orders of magnitude less potent than methatropine while the carboxylate metabolite was found to be one order of magnitude less potent than the soft drugs. A structural isomer of compound 4a was found to be less potent. All the soft drugs tested elicited shorter durations of mydriatic action in rabbit eyes compared to atropine. The untreated eye was dilated in the atropine treated animals while no dilation occurred in the soft drug treated animals indicating facile systemic metabolism of the soft drugs to inactive moieties, possibly the carboxylate metabolite. In in vitro stability studies, the soft drugs have been found to be more hydrolytically labile than atropine. The shorter duration of mydriatic action of compound 4a coupled with increased hydrolytic lability make this a candidate for further study.