Pramoxine Hydrochloride

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Cat Number

API637581

CAS Number

637-58-1

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Product Detail Description Scientific Support Customer Q&A

CAS Number

637-58-1

EINECS

211-293-1

Storage

Store at room temperature

Synonyms

Pramoxine HCl; Pramocaine hydrochloride; Tronothane; DTXSID2047777; NSC-25573; 88AYB867L5; 4-(3-(p-Butoxyphenoxy)propyl)morpholine hydrochloride

Molecular Formula

C17H28ClNO3

Molecular Weight

329.9

Smiles

CCCCOC1=CC=C(C=C1)OCCCN2CCOCC2.Cl

Appearance

White to off-white crystalline powder

Melting Point

181-183°C

Boiling Point

500.1±50.0°C (Predicted)

General Description

Pramoxine hydrochloride is a local anesthetic of the morpholine ether class, structurally distinct from ester or amide local anesthetics. Its chemical name is 4-[3-(4-butoxyphenoxy)propyl]morpholine hydrochloride. The molecule contains a morpholine ring linked via a propyl chain to a butoxyphenoxy group. The hydrochloride salt enhances aqueous solubility. Pramoxine has a unique structure that is neither an ester nor an amide, reducing the risk of cross-sensitivity reactions.

Mechanism of Action

Pramoxine reversibly blocks voltage-gated sodium channels on the neuronal membrane, preventing sodium influx and action potential generation. This inhibits nerve impulse conduction, producing local anesthesia. The drug does not cross intact skin well but is effective on mucous membranes and abraded skin. Unlike ester anesthetics, pramoxine is not metabolized to para-aminobenzoic acid (PABA), thereby minimizing allergic reactions.

Application

Pramoxine is indicated as a topical anesthetic for relief of pain, itching, and discomfort from conditions such as hemorrhoids, pruritus ani, minor burns, insect bites, and skin abrasions. It is also included in combination products with corticosteroids or antiseptics. The drug is available over the counter. Due to its low systemic absorption and low allergenic potential, it is considered safe for repeated use.

Two reversed‑phase liquid chromatographic methods were compared for simultaneous estimation of hydrocortisone acetate and pramoxine hydrochloride in cream in the presence of their degradants. Conventional RPLC (hydro‑organic eluent) offered superior sensitivity for impurities. Micellar liquid chromatography (MLC) using a green, biodegradable mobile phase allowed direct cream injection without laborious sample pretreatment, reducing analysis time and toxic solvent use. MLC is an eco‑friendly alternative, while RPLC is preferable when high impurity sensitivity is required.

Fig. 1 Three-dimensional (3D) plot of a chromatographic run of the studied drugs using DAD detector for (a) MLC and (b) RPLC. (Ibrahim F, et al., 2018)

References

Ibrahim F, et al. Comparative study of two different chromatographic approaches for quantitation of hydrocortisone acetate and pramoxine hydrochloride in presence of their impurities. J Food Drug Anal. 2018;26(3):1160-1170.

Does Pramoxine Hydrochloride require protection from light during storage?

Yes, it is moderately photosensitive. Prolonged light exposure can cause discoloration and degradation. Store in light-resistant containers, preferably amber glass.

What is the recommended storage temperature for Pramoxine Hydrochloride?

Store at controlled room temperature (15-25°C). Avoid excessive heat above 30°C, which can soften the powder and accelerate hydrolysis of the ether linkage.

Is Pramoxine Hydrochloride stable in topical creams, lotions, and sprays?

Yes, when formulated with standard preservatives and antioxidants.

How is the impurity pramoxine N-oxide (an oxidative degradation product) monitored?

This degradation product is quantified using a stability-indicating HPLC method, ensuring it remains within pharmacopoeial limits for topical use.