Local Anesthetics and Topical Antiseptics in the Treatment of Sore Throat

 

Dr. Shoaib Ahmad

University School of Pharmaceutical Sciences, Rayat-Bahra University, Mohali 140104 India

 

ABSTRACT:

Mild to severe sore throat is often associated withe pharyngitis. Lozenges are a traditional treatment of sore throat and reduce discomfort caused by oral inflammation. Amylmetacresol and dichloro-benzylalcohol are topical antiseptics popular Strepsils lozenges. Antibiotics are not recommended for treating sore throat which can be managed by use of local anesthetics as well as topical antiseptics. Present article is an attempt to review the developments in new approach for managing sore throat in clinical conditions.

 

 

INTRODUCTION:

Mild to severe sore throat is usually a characteristic symptom of acute pharyngitis. Sore throat is often accompanied by inflammation. In the later stages, throat pain, pain on swallowing, and burning sensations appear¹. Lozenges have been a traditional treatment of sore throat. They are able to reduce discomfort caused by oral inflammation².   Amylmetacresol (AMC) and dichloro-benzylalcohol (DCBA) are topical antiseptics used in much advertised and familiar Strepsils sore throat lozenges^3,4. Antibiotics are generally not prescribed for treating acute sore throat³.

 

Local Anesthetics and Topical Antiseptics used in sore Throat:

The following drugs are either used in the treatment of sore throat or they have a potential to be used in such cases:

 

Local anesthetics (benzocaine, lignocaine, xylocaine).

Topical antiseptics (hexylresorcinol, amylmetacresol and dichloro-benzylalcohol).

 

Mechanism of Action:

Local anesthetics produce characteristic effect in sore throat because of their sodium channel blocking action^2,4. Topical antiseptics (viz. hexylresorcinol, amylmetacresol and dichloro-benzylalcohol) reversibly block depolarisation-induced inward sodium current².

 

Recent Developments in the Management of sore throat:

Use of Local Anesthetics:

The effect of benzocaine lozenges, nebulised lignocaine and lignocaine spray on upper airway reflex sensitivity was studied. In this experimental investigation, ammonia (low concentration) was used as a stimulus to upper airway receptors. Threshold response of the airway to stimulus (NH3TR) served as main parameter for evaluation of drug response. Ten minutes after taking benzocaine 20 mg lozenge, NH3TR increased from 680 to 975 and returned to baseline after 25 min. Lignocaine 100 mg sprayed onto the vocal cords led to elevation in NH3TR from 665 to 1600 and this effect lasted for 100 min. 4% nebulised lignocaine 4 ml increased NH3TR from 770 to 1190 and the effect persisted for 30 min⁵. A randomised, double-blind phase III trial was conducted for determining the efficacy and safety of lidocaine acetamide 8 mg lozenges. These lozenges emerged to be a favourable option for relieving pain in an acute sore throat¹. Topical xylocaine spray was used as a topical pharyngeal anesthesia⁶.

 

Use of Topical Antiseptics:

The effect of topical antiseptics (viz. hexylresorcinol, amylmetacresol and dichloro-benzylalcohol) was studied on voltage-operated neuronal sodium channels in HEK 293 cells. All the three antiseptics reversibly blocked inward sodium currents. This sodium channel-blocking action has a fair resemblance to local anesthesia effects. Hexylresorcinol and amylmetacresol were found 10-20 times more potent than lidocaine².  A clinical study was conducted to evaluate to the effectiveness of Strepsils Dual Action anesthetic lozenge plus distilled water spray for pharyngeal anesthesia⁶.  In a randomised controlled trial, AMC/DCBA throat lozenges were found to reduce throat soreness within 5 min of first dose³. AMC/DCBA lozenges produce local anaesthesia-like effects⁴. Postoperative sore throat (POST) due to tracheal intubation is self-limiting. POST is considered most undesirable anesthetic outcomes. Lozenges containing amyl-m-cresol is understood to have reduced POST⁷.

 

Use of a combination of Local anesthetics and topical antiseptics:

A clinical study was conducted to evaluate to the effectiveness of xylocaine spray and anesthetic lozenges as a topical pharyngeal anesthesia for unsedated esophagogastroduodenoscopy. Patients received one of the following treatments:

a.        10% Xylocaine pump spray plus plain Strepsils

b.       Strepsils Dual Action anesthetic lozenge plus distilled water spray

 

Patients in the first group had a higher tolerance, higher intensity of numbness and less discomfort than the second group. Topical Xylocaine spray appeared better treatment than lozenges as a topical pharyngeal anesthesia⁶. A randomised, double-blind study of a single dose of two types of lozenges in acute sore throat was conducted. The subjects received either AMC/DCBA + lidocaine lozenge or a hexylresorcinol lozenge. Both lozenges had fast onset of action (within 10 minutes).Both lozenges were very well tolerated. They provided rapid and effective sore throat relief in patients⁸.A study demonstrated local anaesthetic-like effects of AMC/DCBA lozenges. It was shown that in the presence of AMC, DCBA and lidocaine, a prominent block of inward sodium current took place⁴.

 

Current and Potential Uses of Lozenges:

1.        Acute sore throat.

2.        Upper airway reflex sensitivity.

3.        Topical pharyngeal anesthesia.

4.        Topical pharyngeal anesthesia for unsedated esophagogastroduodenoscopy.

5.        Postoperative sore throat.

 

CONCLUSIONS:

Sore throat is a characteristic symptom of inflammation of pharynx known as acute pharyngitis. It can be managed by use of local anesthetics (benzocaine, lignocaine, xylocaine) as well as topical antiseptics (hexylresorcinol, amylmetacresol and dichloro-benzylalcohol). Both types of drugs cause sodium channel blockade to relieve sore throat. OTC lozenge formulations based on topical antiseptics are a convenient treatment option which provides relief from the sore throat within 10 minutes time.

 

ACKNOWLEDGEMENTS:

Author acknowledges the support from Dr. Shibli Jamil, author's family and Rayat-Bahra University, Mohali.

 

REFERENCES:

1.        Wonnemann M, Helm I, Stauss-Grabo M, et al. Lidocaine 8 mg sore throat lozenges in the treatment of acute pharyngitis. A new therapeutic option investigated in comparison to placebo treatment. Arzneimittelforschung 2007; 57(11):689-97.

2.        Buchholz V, Leuwer M, Ahrens J, et al. Topical antiseptics for the treatment of sore throat blocks voltage-gated neuronal sodium channels in a local anaesthetic-like manner. Naunyn Schmiedebergs Arch Pharmacol 2009; 380(2):161-8.

3.        McNally D, Simpson M, and Morris C, et al. Rapid relief of acute sore throat with AMC/DCBA throat lozenges: randomised controlled trial. Int. J. Clin Pract 2010; 64(2):194-207.

4.        Foadi N, de Oliveira RC, Buchholz V, et al. A combination of topical antiseptics for the treatment of sore throat blocks voltage-gated neuronal sodium channels. Naunyn Schmiedebergs Arch Pharmacol 2014; 387(10):991-1000.

5.        Raphael JH, Stanley GD, Langton JA. Effects of topical benzocaine and lignocaine on upper airway reflex sensitivity. Anaesthesia 1996; 51(2):114-8.

6.        Chan CK, Fok KL, Poon CM. Flavored anesthetic lozenge versus Xylocaine spray used as topical pharyngeal anesthesia for un sedated esophagogastroduodenos copy: a randomized placebo-controlled trial. Surg Endosc 2010; 24(4):897-901.

7.        Kalil DM, Silvestro LS, Austin PN. Novel preoperative pharmacologic methods of preventing postoperative sore throat due to tracheal intubation. AANA J 2014; 82(3):188-97.

8.        McNally D, Shephard A, Field E. Randomized, double-blind, placebo-controlled study of a single dose of an amylmetacresol/2,4-dichlorobenzyl alcohol plus lidocaine lozenge or a hexylresorcinol lozenge for the treatment of acute sore throat due to upper respiratory tract infection. J Pharm. Pharm. Sci. 2012; 15(2):281-94.

 

 

 

 

 

Received on 08.03.2017          Modified on 20.04.2017

Accepted on 29.04.2017      ©A&V Publications All right reserved