Description
Cyclopentolate is an antagonist of muscarinic acetylcholine receptors (K
is = 1.62, 27.5, and 2.63 nM for M
1, M
2, and M
3 receptors, respectively).
1 It inhibits carbachol-induced contraction of isolated human iris sphincter, circular ciliary muscle, and longitudinal ciliary muscle (K
bs = 7.9, 15.8, and 12.5 nM, respectively).
2 Formulations containing cyclopentolate have been used to induce pupil dilation and to prevent the eye from accommodating for near vision.
Chemical Properties
White Solid
Originator
Cyclogyl,Schieffelin,US,1953
Uses
Mydriatic;Cholinergic receptor antagonist
Definition
ChEBI: Cyclopentolate hydrochloride is the hydrochloride salt of cyclopentolate. It is used to produce mydriasis (excessive dilation of the pupil) and cycloplegia (paralysis of the ciliary muscle of the eye) for opthalmic diagnostic procedures. It acts more quickly than atropine and has a shorter duration of action. It has a role as a mydriatic agent, a parasympatholytic, a diagnostic agent and a muscarinic antagonist. It contains a cyclopentolate.
Manufacturing Process
To a well stirred suspension of 9 g of sodium phenyl acetate and 2.4 g of
magnesium turnings in 25 cc of anhydrous ether, a solution of 9.4 cc of
isopropyl bromide in 50 cc of anhydrous ether are added. The mixture is
refluxed for one hour (during which time propane is evolved) and then 5 cc of
cyclopentanone in 25 cc of anhydrous ether are added dropwise. The mixture
is then refluxed for one hour and poured over ice water containing some
hydrochloric acid. The ether solution is separated and extracted with 200 cc of
5% sodium hydroxide. The alkaline solution on acidification gives the free acid which is filtered off, dried in a desiccator and recrystallized from a mixture of
ethylene dichloride and petroleum ether.
The product is 2-phenyl-2-(1-hydroxycyclopentyl)ethanoic acid, melting at 95°
to 97°C. Of this product, 4.5 g in 30 cc of dry isopropyl alcohol are refluxed
for 16 hours with 2.5 g of β-chloroethyl dimethyl amine. The solution is cooled
and filtered clear from the solid by-product. The solvent is removed under
reduced pressure on the steam bath and the residue is washed with
anhydrous ether. It is dissolved in ethyl acetate from which it crystallizes. It is
the hydrochloride of β-(dimethylamino)ethyl ester of 2-phenyl-2-(1-
hydroxycyclopentyl) ethanoic acid, melting at 134° to 136°C.
Brand name
Akpentolate (Akorn); Cyclogyl (Alcon); Pentolair (Bausch & Lomb); Pentolair (Pharmafair).
Therapeutic Function
Anticholinergic (ophthalmic)
General Description
Cyclopentolatehydrochloride, 2-dimethylaminoethyl 1-hydroxy- -phenylcyclopentaneacetatehydrochloride (Cyclogyl), is a crystalline,white, odorless solid that is very soluble in water,easily soluble in alcohol, and only slightly soluble in ether.A 1% solution has a pH of 5.0 to 5.4.
Cyclopentolate hydrochloride has one half of the antispasmodicactivity of atropine and is nonirritating when instilledrepeatedly into the eye. If not neutralized after the refractionstudies, its effect dissipates within 24 hours. Neutralizationwith a few drops of pilocarpine nitrate solution, 1% to 2%,often results in complete recovery in 6 hours. It is supplied asa ready-made ophthalmic solution in concentrations of either0.5% or 2%.
Clinical Use
Cyclopentolate Hydrochloride is used only for its effects on the eye, where it acts asa parasympatholytic. When placed in the eye, it quickly producescycloplegia and mydriasis. Its primary field of usefulnessis in refraction studies. Cyclopentolate hydrochloridecan be used, however, as a mydriatic in the management ofiritis, iridocyclitis, keratitis, and choroiditis. Although itdoes not seem to affect intraocular tension significantly, it isbest to be very cautious with patients with high intraocularpressure and with elderly patients with possible unrecognizedglaucomatous changes.
References
[1] S LAZARENO F F R N J Buckley. Characterization of muscarinic M4 binding sites in rabbit lung, chicken heart, and NG108-15 cells.[J]. Molecular Pharmacology, 1990, 38 6: 805-815.
[2] H ISHIKAWA P N P L DeSantis. Selectivity of muscarinic agonists including (+/-)-aceclidine and antimuscarinics on the human intraocular muscles.[J]. Journal of Ocular Pharmacology and Therapeutics, 1998, 14 4: 363-373. DOI:
10.1089/jop.1998.14.363
