Benzocaine

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DRUGS
Benzocaine

Benzocaine is a local anesthetic which works by blocking nerve signals in your body. Benzocaine topical is used to reduce pain or discomfort caused by minor skin irritations, sore throat, sunburn, teething pain, vaginal or rectal irritation, ingrown toenails, hemorrhoids, and many other sources of minor pain on a surface of the body. 

Introduction

Benzocaine is a local anesthetic which works by blocking nerve signals in your body. Benzocaine topical is used to reduce pain or discomfort caused by minor skin irritations, sore throat, sunburn, teething pain, vaginal or rectal irritation, ingrown toenails, hemorrhoids, and many other sources of minor pain on a surface of the body. Benzocaine is also used to numb the skin or surfaces inside the mouth, nose, throat, vagina, or rectum to lessen the pain of inserting a medical instrument such as a tube or speculum

Pharmacological class: Local Anesthetic

Indications

  • Pain or discomfort

 

Pharamcological Action

Benzocaine shows its effects by binding to the sodium channel. It reversibly stabilizes the neuronal membrane which decreases its permeability to sodium ions. Depolarization of the neuronal membrane is inhibited, thereby blocking the initiation and conduction of nerve impulses.

Dosage

  • Bee Stings, Minor Burns, Sunburn, Insect Bites: 5-20% to affected area
  • Mouth and Gum Irritation: 10-20% solution or other topical formulation
  • Sore Throat/Mouth Pain: 1 lozenge dissolved in mouth
  • Dental pain: 2.5-20% solution or other topical formulation
  • Boils: 20% to affected area

Pharmacokinetics

Benzocaine is poorly absorbed through intact skin and get readily absorbed from mucous membranes. The peak plasma time is 1 minutes. It gets metabolized by plasma cholinesterases and to a lesser extent by hepatic cholinesterases. The metabolites are usually excreted in urine.

Contraindications

  • Contraindicated in pregnancy.
  • Contraindicated in patients with known allergy to anesthetics.
  • Contraindicated in patients with middle ear infection or hole in the ear drum.
  • Contraindicated in patients with known condition of increased mast cells.

Drug Interactions

  • No significant interactions known for benzocaine.
  • The antibacterial activity of sulfonamides is reduced when used with benzocaine.

Side effects

Common (affecting between 1 in10 to 1 in 100)

  • Giant Hives
  • Itching
  • Rash
  • Redness of Skin
  • Skin Inflammation due to a Topically Applied Medication
  • Stinging of Skin
  • Skin Irritation

Uncommon (affecting 1 in 100 to 1 in 1000)

  • Confused
  • Dizzy
  • Extreme Sense of Well Being
  • Feeling Cold
  • Feeling Warm
  • Nervous
  • Ringing in the Ears
  • Throwing Up
  • Twitching
  • Visible Water Retention

Very rare (affecting less than 1 in 10,000)

  • Abnormal Heart Rhythm
  • Abnormally Low Blood Pressure
  • Decreased Lung Function
  • Drowsiness
  • Head Pain
  • Involuntary Quivering
  • Life Threatening Allergic Reaction
  • Lung Failure causing Loss of Breath
  • Seizures
  • Slow Heartbeat
  • Toxic Effect on Brain or Spinal Cord Function
  • Turn Blue
  • Unconscious

Precautions

  • Avoid in a child younger than two years old without talking to your doctor. 
  • Avoid in patients with pregnancy or breastfeeding women.
  • Contact physician if pharyngitis persists >48 hr.
  • Methemoglobinemia may occur as a rare event. Physician must be contacted in occurrence of such event.

Clinic Evidence

Thirty patients with spontaneous pain of moderate or severe intensity from a single tooth due to caries, a lost restoration, or a fracture entered this randomized, parallel group, double-blind study. Before self-applying 20% benzocaine gel or placebo, patients read a label containing new dosing directions, including a picture of how much product to apply to their tooth and the surrounding gingival tissues. It was found that 86.7% of the subjects (26/30) applied < or = 375 mg of product (mean +/- SD = 327.7 +/- 276.8 mg). The benzocaine group had a significantly higher (p = 0.022) responder rate (86.7%) than the placebo group (46.7%). Significant differences in favor of the benzocaine group were also recorded for PRID at 10, 15, and 30 minutes (p < 0.05) and SPRID-30 (p = 0.037). Median onset and duration times were 8.3 minutes and > 115 minutes for the benzocaine group, >120 minutes and 5 minutes for the placebo group. There were no adverse events recorded in the study.1

References

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