Docosanol - About an On-Hand Remedy for Herpes Labialis

Overview

Docosanol is a topical antiviral agent used for the treatment of herpes labialis. It was approved by the United States Food and Drug Administration (FDA) on July 25, 2000, for external use on herpes sores that commonly occur around the orofacial region, such as the mouth, tongue, and lips. It is the only FDA-approved over-the-counter (OTC) topical cream for healing sores caused by herpes simplex virus (HSV).

Docosanol is significantly well tolerated, and its clinical efficacy has been established through various scientific studies. It is the drug of choice, especially for recurrent herpes simplex labialis lesions, as it heals the sores faster. Docosanol is a saturated 22-carbon aliphatic alcohol exhibiting antiviral activity against several lipid-enveloped viruses like herpes simplex virus (HSV). Although it does show direct virucidal characteristics, it prevents viral binding to the host cells, thereby blocking viral replication.

Indications:

The topical use of Docosanol is indicated in the following clinical conditions-

• To treat orofacial herpes simplex, commonly known as cold sores or fever blisters.

• To cure recurrent episodes of herpes simplex labialis that are usually painful.

• It also combines therapeutic regimes with topical nucleosides and oral antivirals in severe herpetic infections.

• Its use is indicated for adults and children over 12 years of age.

Therapeutic Uses:

Docosanol exhibits a wide range of therapeutic benefits, which are as follows -

• It markedly reduces the pain associated with herpetic sores.

• It shortens the healing time by 0.7 days and resolves the related symptoms by about 0.5 days.

• It effectively reduces clinical symptoms such as pain, tingling or burning sensations, and itching that occurs due to herpetic sores.

• Docosanol is safe and markedly effective in treating recurrent herpes labialis lesions.

• Docosanol's antiviral properties and anti-inflammatory effects considerably reduce the relapse of cold sores.

Contraindications:

The use of Docosanol is contraindicated in individuals with a known history of developing hypersensitivity or an anaphylactic response to Docosanol. Also, it is not recommended for individuals who develop allergic reactions to Docosanol.

Special Considerations

• Pediatric Use - A doctor should be consulted for children below 12 years of age, and Docosanol should be used with caution since no scientific evidence exists for its use in younger age groups.

• Pregnancy - The pregnancy risk for Docosanol is category C, meaning risk potential cannot be neglected. The studies assessing its effect on pregnant women are inadequate, and some animal experiments have demonstrated fetal toxicity. Hence, the use of Docosanol in pregnant women must outweigh the risks compared to its potential therapeutic benefits.

• Lactation and Breastfeeding - No clinical data are available for its use during breastfeeding. Lactating mothers should consult their physician or healthcare provider before starting Docosanol.

Available Forms and Strengths

• Docosanol is available in two-gram OTC (over-the-counter) tubes containing 10 percent Docosanol cream for topical use to treat oro-labial sores of herpes simplex.

• Its composition includes benzyl alcohol, propylene glycol, mineral oil, sucrose stearate, sucrose di-stearate, and purified water.

Directions for Use:

Docosanol is recommended for adult individuals and children who are more than 12 years of age. The following steps are followed for its application.

• Dosage - 10 percent Docosanol cream is topically applied five times daily until the sores subside or disappear.

• The dosing of Docosanol depends on the individual's infection type, treatment response, and medical condition.

• The individual applying the medication should wash the hands thoroughly before applying the cream. The hands should be dry before taking the cream on their fingertips.

• An adequate amount of Docosanol cream is taken and applied to the affected area where the sores are present (face and lips).

• Starting Docosanol immediately upon experiencing the initial sign of a fever blister, such as a tingling sensation (prodromal stage), ensures early recovery and a better therapeutic outcome.

• Docosanol cream must be rubbed gently over the affected area and completely cover the lesion, including its margins.

• Proper hand washing is recommended after applying Docosanol cream on the affected area.

• The medication should be continued until complete healing is witnessed. Irregular application or discontinuation of the drug leads to the recurrence of herpetic lesions.

For Patients

What Causes Herpes Labialis?

Herpes labialis refers to commonly occurring oral and facial viral infections that primarily develop on the oral mucosa and the lips. Herpes simplex type 1 (HSV-1) virus predominantly causes herpes labialis and is also responsible for its relapse. The HSV type 2 virus can potentially cause primary herpes labialis; however, recurrence rarely occurs in HSV type 2 infections. The lesions of herpes labialis initially start as rashes on the oral mucous membrane (specifically the vermilion border in the lips) or skin (nose, cheek, or chin) and result in blister formation (fever blister or core sore).

The classical prodromal (early indications before the clinical onset of an illness) signs of herpes labialis are as follows -

• Burning sensation or pain.

• Tingling sensation.

• Itching.

• Erythematous (abnormal skin reddening) changes.

• Cutaneous (skin) eruptions or bumps.

Herpes labialis is a self-limiting viral infection in healthy (immunocompetent) individuals and spontaneously heals within a duration of 10 days. However, it is highly contagious (spreading). It readily gets transmitted to individuals who were not exposed to HSV previously and also to people with weak immunity, like individuals infected with the human immunodeficiency virus (HIV), patients on chemotherapy, and individuals under immunosuppressive therapies. Herpes labialis infections could further extend and cause genital herpetic lesions (sores or blisters in the genital region) through unprotected orogenital transmission.

Is Herpes Labialis Curable?

Herpes labialis is treatable and preventable if proper therapeutic interventions are started during the early phase of the illness (within one to two days of onset). Several topical (nonspecific creams, anesthetic medications, and antiviral creams) and oral antivirals (Acyclovir, Valacyclovir, and Famciclovir) are available to manage herpes labialis. Antiviral oral prophylaxis is recommended for individuals with a known history of recurrent episodes of herpes labialis.

How Does Docosanol Work on Herpes Labialis?

Docosanol is the prescribed topical (external use only) antiviral recommended for treating herpes labialis caused by HSV. It is the primary drug preferred for managing recurrent episodes of herpes labialis infections (repeated occurrences of cold sores and fever blisters). Chemically, Docosanol is made of saturated long-chain alcohol, which effectively blocks HSV replication. Docosanol exerts its antiviral activity in the following ways -

• Docosanol disrupts the attachment of viral particles to the host (human) cells by inhibiting the viral fusion with the cell membrane.

• This prevents the entry of herpes simplex virus (HSV) into the host cells and eventually stops its replication.

• Thus, Docosanol therapeutically inhibits HSV from invading normal and healthy skin tissues.

How to Use Docosanol?

Following proper directions and recommendations for Docosanol use as instructed by a physician or healthcare provider helps in optimal recovery from herpes labialis infection and also considerably prevents its relapse.

• The use of Docosanol is initiated when the first signs of herpes labialis (prodromal signs) are noticed, like redness of the skin, pain, or burning sensation.

• Before applying the cream, hands should be washed thoroughly and dried completely.

• The affected area where Docosanol is applied should be cleaned and dried before application.

• An appropriate amount of the medication is taken on the fingertips, and a thin layer of the cream is applied, completely covering the affected area (visible blisters or areas having prodromal signs), including the edges of the cold sores.

• Docosanol cream is rubbed gently every three to four hours (five times per day) or as instructed by the doctor.

• After applying, hands should be thoroughly washed with soap and water to prevent further transmission of the herpes virus.

• The medication is only for external use and should only be applied to the skin.

• Topical application of Docosanol should continue until sores are completely healed, and the doctor should be consulted before stopping the treatment.

Does Docosanol Cause Any Side Effects?

Docosanol is a well-tolerated and safe medication that does not produce severe adverse reactions. However, some of the following side effects are rarely reported.

• Allergic responses like rashes and urticaria (hives).

• Itching, reddening of the skin, and localized edema (mouth, lips, tongue, face, and throat).

• Peeling of skin or blisters.

• Fever.

• Wheezing or troubled breathing.

• Chest tightness.

• Difficulty swallowing or tightness in the throat.

• Abnormal hoarseness of voice.

• Extreme irritation on the skin surface where the medication was applied.

What Precautions Are to Be Followed While Using Docosanol?

The warnings and precautions to be followed during Docosanol treatment are as follows -

• Avoid contact with eyes and nearby areas, as Docosanol could cause eye irritation. In case of accidental contact, the eyes should be washed thoroughly with plenty of clear water (do not use warm water or soap).

• Docosanol cream should not be applied inside the nose or mouth. It is for external use only. Accidental swallowing must be reported immediately to the poison control center, and patients should seek medical assistance.

• This medication is not prescribed for treating canker sores (common sores found in the mouth), genital herpes, or shingles (herpes zoster). Its use should be avoided in such cases.

• Any cosmetics applied to the affected area must be removed before applying the medication. Cosmetics could be used after applying the drug, but care should be taken to use a disposable applicator to prevent infection spread.

• Dosing of Docosanol is customized to the individual’s needs; therefore, over-usage or deficient application should be avoided.

• Regular use and completing the prescribed treatment duration are essential for a better outcome.

• To avoid missed doses, use the medication consistently for the same period. If a missed schedule can be applied when remembered, avoid over-usage.

• Herpes labialis could spread even during treatment; hence, avoid close skin contact with other people.

• If any side effect develops or the sores worsen, it should be immediately reported to the healthcare provider or physician.

• Docosanol cream should be kept in its original container (tube) in a dry, cool place away from moisture and direct sunlight. It should not be refrigerated or frozen.

• It should be kept out of reach of children, and unused, damaged, or expired tubes should be properly disposed of.

• The tube should be kept closed and uncapped for a prolonged period, as it reduces the efficacy of the drug.

For Doctors

Pharmacodynamics

Docosanol is a potent antiviral used in the topical treatment of herpes labialis. It exerts its antiviral activity over various enveloped (made of lipids) viruses, such as herpes simplex. The 22-carbon saturated aliphatic chains that constitute Docosanol inhibit viral adhesion and replication.

Docosanol is the preferred therapeutic choice for cold sores because it accelerates the healing duration of fever blisters/cold sores, especially in the oro-facial regions. Further, it relieves the associated prodromal symptoms like tingling, burning pain, and itching. Also, Docosanol is used to manage recurrent herpes labialis lesions effectively.

Mechanism of Action

Docosanol is classified as a topical antiviral agent, and it possesses the following mechanism of action -

• Docosanol interferes with the fusion between the host cell's plasma membrane and the lipid envelope of the herpes simplex virus (HSV).

• This mechanism prevents viral entry into human cells and consequently inhibits viral attachment and replication.

• Recent studies have also demonstrated the anti-inflammatory action of Docosanol on HSV.

• Docosanol does not possess direct virucidal properties, and its primary anti-HSV mechanism is associated with viral-host cell fusion interference, so it does not develop HSV drug-resistant mutants.

Pharmacokinetics

• Route of Administration - Topical application over the affected area.

• Absorption - Following topical application, Docosanol shows minimal absorption into the bloodstream, reflecting its use for normal clinical conditions.

• Studies show that the plasma levels of Docosanol after application are negligible, indicating reduced drug toxicity and minimal drug interactions.

• Metabolism - Radiolabelled analysis of Docosanol pharmacokinetics proves that Docosanol undergoes cellular uptake, and its metabolism occurs within host cells.

• A notable quantity of n-docosanol (active ingredient) undergoes oxidation. It gets converted to n-docosanoic acid, which gets incorporated into polar lipids present on the surface of the host cell membrane.

• Further research and clinical trials are needed to assess the distribution, protein binding, and elimination of Docosanol, and also related pharmacokinetic aspects.

Chemical taxonomy:

• Kingdom - Organic compound.

• Super Class - Lipids and lipid-derived molecules.

• Class - Fatty acyl.

• Sub Class - Fatty alcohol.

• Direct Parent Compound - Fatty alcohol.

• Alternative Parent Compound - Primary alcohol and hydrocarbon derivatives.

• Substituents - Alcohol, hydrocarbon derivative, aliphatic, acyclic compound, and a primary alcohol.

• Molecular Framework - Aliphatic, acyclic compound.

• External Descriptor - Long-chain primary fatty alcohols or long-chain alcohols.

Toxicities and Drug Interactions:

Toxicities to Docosanol are generally associated with overdoing or extended drug usage beyond the prescribed duration.

Some of the clinical signs of its toxicity are as follows -

• Headache.

• Abdominal pain.

• Elevated levels of serum lipase.

• Nausea.

• Dyspepsia.

• Dizziness.

• Hyperbilirubinemia.

• Localized reactions like skin inflammation and dryness of the skin.

Drug Interactions:

Since plasma levels of Docosanol are negligible, no significant drug interactions are documented. However, the combined use of Docosanol with oral antivirals produces a synergistic effect and enhances the therapeutic outcome of herpes labialis.