Topical anesthetic
Encyclopedia
A topical anesthetic is a local anesthetic
that is used to numb the surface of a body part. They can be used to numb any area of the skin
as well as the front of the eyeball, the inside of the nose
, ear
or throat
, the anus
and the genital area. Topical anesthetics are available in creams, ointments, aerosols, sprays, lotions, and jellies. Examples include benzocaine
, butamben
, dibucaine, lidocaine
, oxybuprocaine
, pramoxine, proparacaine, proxymetacaine
, and tetracaine
(also named amethocaine).
and itching
caused by conditions such as sunburn or other minor burns, insect bites or stings, poison ivy
, poison oak
, poison sumac
, and minor cuts and scratches.
Topical anesthetics are used in ophthalmology
and optometry
to numb the surface of the eye
(the outermost layers of the cornea
and conjunctiva
) to:
In dentistry
, topical anesthetics are used to numb oral tissues before administering a dental local anesthetic
.
Some topical anesthetics are also used in otolaryngology
, like for example oxybuprocaine
.
Topical anesthetics are now commonly used in the temporary relief of premature ejaculation when applied to the Glans (head) of the penis. Benzocaine or lidocaine are typically used for this purpose as they are available OTC (lidocaine is more powerful than benzocaine).
masquerading as acanthamoeba keratitis
or other infectious keratitis. When a keratitis is unresponsive to treatment and associated with strong ocular pain, topical anesthetic abuse should be considered, and a history of psychiatric disorders and other substance abuse have been implicated as important factors in the diagnosis. Because of the potential for abuse, clinicians have been warned about the possibility of theft and advised against prescribing topical anesthetics for therapeutic purposes.
Some patients who suffer from eye pain, which is often considerably strong neuropathic pain
caused by the irritation of the nerves within the cornea and/or conjunctiva, unfortunately try to illegally obtain oxybuprocaine or other eye anesthetics (for example by stealing
them at their ophthalmologist or optometrist, by forging
medical prescription
s or by trying to order it via an online pharmacy
) and secretly use the substance to numb their eye pain, often ending up with irreversible corneal damage or even destruction (which is a vicious cycle and causes even much more pain). Often, such patients finally require corneal transplantation
.
In case of prolonged or chronic eye pain, especially neuropathic eye pain, it is highly advisable to use centrally
acting substances like anticonvulsants (pregabalin
, gabapentin
and in more serious cases carbamazepine
) or antidepressants (for example SSRIs or the tricyclic antidepressant
amitriptyline
). Even very small amounts of an anticonvulsant and/or an antidepressant can almost completely stop eye pain and does not damage the eye at all.
Local anesthetic
A local anesthetic is a drug that causes reversible local anesthesia, generally for the aim of having local analgesic effect, that is, inducing absence of pain sensation, although other local senses are often affected as well...
that is used to numb the surface of a body part. They can be used to numb any area of the skin
Human skin
The human skin is the outer covering of the body. In humans, it is the largest organ of the integumentary system. The skin has multiple layers of ectodermal tissue and guards the underlying muscles, bones, ligaments and internal organs. Human skin is similar to that of most other mammals,...
as well as the front of the eyeball, the inside of the nose
Human nose
The visible part of the human nose is the protruding part of the face that bears the nostrils. The shape of the nose is determined by the ethmoid bone and the nasal septum, which consists mostly of cartilage and which separates the nostrils...
, ear
Ear
The ear is the organ that detects sound. It not only receives sound, but also aids in balance and body position. The ear is part of the auditory system....
or throat
Throat
In vertebrate anatomy, the throat is the anterior part of the neck, in front of the vertebral column. It consists of the pharynx and larynx...
, the anus
Anus
The anus is an opening at the opposite end of an animal's digestive tract from the mouth. Its function is to control the expulsion of feces, unwanted semi-solid matter produced during digestion, which, depending on the type of animal, may be one or more of: matter which the animal cannot digest,...
and the genital area. Topical anesthetics are available in creams, ointments, aerosols, sprays, lotions, and jellies. Examples include benzocaine
Benzocaine
Benzocaine is a local anesthetic commonly used as a topical pain reliever, or in cough drops. It is the active ingredient in many over-the-counter anesthetic ointments...
, butamben
Butamben
Butamben is a local anesthetic . It is the ester of 4-aminobenzoic acid and butanol....
, dibucaine, lidocaine
Lidocaine
Lidocaine , Xylocaine, or lignocaine is a common local anesthetic and antiarrhythmic drug. Lidocaine is used topically to relieve itching, burning and pain from skin inflammations, injected as a dental anesthetic or as a local anesthetic for minor surgery.- History :Lidocaine, the first amino...
, oxybuprocaine
Oxybuprocaine
Oxybuprocaine , also known as benoxinate or BNX, is the name of a local anesthetic, which is used especially in ophthalmology and otolaryngology...
, pramoxine, proparacaine, proxymetacaine
Proxymetacaine
Proxymetacaine or proparacaine is a topical anesthetic drug of the aminoester group.-Indications and usage:Proxymetacaine hydrochloride ophthalmic solution is indicated for procedures such as tonometry, gonioscopy, removal of foreign bodies, or other similar procedures requiring topical...
, and tetracaine
Tetracaine
Tetracaine is a potent local anesthetic of the ester group...
(also named amethocaine).
Usage
Topical anesthetics are used to relieve painPain
Pain is an unpleasant sensation often caused by intense or damaging stimuli such as stubbing a toe, burning a finger, putting iodine on a cut, and bumping the "funny bone."...
and itching
Itch
Itch is a sensation that causes the desire or reflex to scratch. Itch has resisted many attempts to classify it as any one type of sensory experience. Modern science has shown that itch has many similarities to pain, and while both are unpleasant sensory experiences, their behavioral response...
caused by conditions such as sunburn or other minor burns, insect bites or stings, poison ivy
Poison ivy
Toxicodendron radicans, better known as poison ivy , is a poisonous North American plant that is well known for its production of urushiol, a clear liquid compound found within the sap of the plant that causes an itching rash in most people who touch it...
, poison oak
Poison oak
Poison oak may refer to* Toxicodendron diversilobum, grows on West Coast of North America* Toxicodendron pubescens, grows in the Eastern United Statesdamnnnnn tissss is terribleee...
, poison sumac
Poison Sumac
Poison sumac is a woody shrub or small tree growing to 7 m tall. All parts of the plant contain a resin called urushiol that causes skin and mucous membrane irritation to humans...
, and minor cuts and scratches.
Topical anesthetics are used in ophthalmology
Ophthalmology
Ophthalmology is the branch of medicine that deals with the anatomy, physiology and diseases of the eye. An ophthalmologist is a specialist in medical and surgical eye problems...
and optometry
Optometry
Optometry is a health care profession concerned with eyes and related structures, as well as vision, visual systems, and vision information processing in humans. Optometrists, or Doctors of Optometry, are state licensed medical professionals trained to prescribe and fit lenses to improve vision,...
to numb the surface of the eye
Human eye
The human eye is an organ which reacts to light for several purposes. As a conscious sense organ, the eye allows vision. Rod and cone cells in the retina allow conscious light perception and vision including color differentiation and the perception of depth...
(the outermost layers of the cornea
Cornea
The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber. Together with the lens, the cornea refracts light, with the cornea accounting for approximately two-thirds of the eye's total optical power. In humans, the refractive power of the cornea is...
and conjunctiva
Conjunctiva
The conjunctiva covers the sclera and lines the inside of the eyelids. It is composed of rare stratified columnar epithelium.-Function:...
) to:
- Perform a contact/applanation tonometryTonometryTonometry is the procedure eye care professionals perform to determine the intraocular pressure , the fluid pressure inside the eye. It is an important test in the evaluation of patients at risk from glaucoma...
. - Perform a Schirmer's testSchirmer's testSchirmer's test determines whether the eye produces enough tears to keep it moist. This test is used when a person experiences very dry eyes or excessive watering of the eyes. It poses no risk to the subject. A negative test result is normal...
(The Schirmer's testSchirmer's testSchirmer's test determines whether the eye produces enough tears to keep it moist. This test is used when a person experiences very dry eyes or excessive watering of the eyes. It poses no risk to the subject. A negative test result is normal...
is sometimes used with a topicalTopicalIn medicine, a topical medication is applied to body surfaces such as the skin or mucous membranes such as the vagina, anus, throat, eyes and ears.Many topical medications are epicutaneous, meaning that they are applied directly to the skin...
eye anesthetic, sometimes without. The use of a topical anesthetic might impede the reliability of the Schirmer's test and should be avoided if possible.). - Remove small foreign objects from the uppermost layer of the cornea or conjunctiva. The deeper and the larger a foreign object which should be removed lies within the cornea and the more complicated it is to remove it, the more drops of topical anesthetic are necessary prior to the removal of the foreign object to numb the surface of the eye with enough intensity and duration.
In dentistry
Dentistry
Dentistry is the branch of medicine that is involved in the study, diagnosis, prevention, and treatment of diseases, disorders and conditions of the oral cavity, maxillofacial area and the adjacent and associated structures and their impact on the human body. Dentistry is widely considered...
, topical anesthetics are used to numb oral tissues before administering a dental local anesthetic
Local anesthetic
A local anesthetic is a drug that causes reversible local anesthesia, generally for the aim of having local analgesic effect, that is, inducing absence of pain sensation, although other local senses are often affected as well...
.
Some topical anesthetics are also used in otolaryngology
Otolaryngology
Otolaryngology or ENT is the branch of medicine and surgery that specializes in the diagnosis and treatment of ear, nose, throat, and head and neck disorders....
, like for example oxybuprocaine
Oxybuprocaine
Oxybuprocaine , also known as benoxinate or BNX, is the name of a local anesthetic, which is used especially in ophthalmology and otolaryngology...
.
Topical anesthetics are now commonly used in the temporary relief of premature ejaculation when applied to the Glans (head) of the penis. Benzocaine or lidocaine are typically used for this purpose as they are available OTC (lidocaine is more powerful than benzocaine).
Duration of topical
The duration of topical anesthesia might depend on the type and amount applied, but is usually about half an hour.Abuse when used for ocular pain relief
When used excessively, topical anesthetics can cause severe and irreversible damage to corneal tissues and even loss of the eye. The abuse of topical anesthetics often creates challenges for correct diagnosis in that it is a relatively uncommon entity that may initially present as a chronic keratitisKeratitis
Keratitis is a condition in which the eye's cornea, the front part of the eye, becomes inflamed. The condition is often marked by moderate to intense pain and usually involves impaired eyesight.-Types:...
masquerading as acanthamoeba keratitis
Acanthamoeba keratitis
Acanthamoeba keratitis is a rare disease in which amoebae invade the cornea of the eye.-Causes:In the United States, it is nearly always associated with contact lens use, as Acanthamoeba can survive in the space between the lens and the eye...
or other infectious keratitis. When a keratitis is unresponsive to treatment and associated with strong ocular pain, topical anesthetic abuse should be considered, and a history of psychiatric disorders and other substance abuse have been implicated as important factors in the diagnosis. Because of the potential for abuse, clinicians have been warned about the possibility of theft and advised against prescribing topical anesthetics for therapeutic purposes.
Some patients who suffer from eye pain, which is often considerably strong neuropathic pain
Neuropathic pain
Neuropathic pain results from lesions or diseases affecting the somatosensory system. It may be associated with abnormal sensations called dysesthesia, which occur spontaneously and allodynia that occurs in response to external stimuli. Neuropathic pain may have continuous and/or episodic ...
caused by the irritation of the nerves within the cornea and/or conjunctiva, unfortunately try to illegally obtain oxybuprocaine or other eye anesthetics (for example by stealing
Theft
In common usage, theft is the illegal taking of another person's property without that person's permission or consent. The word is also used as an informal shorthand term for some crimes against property, such as burglary, embezzlement, larceny, looting, robbery, shoplifting and fraud...
them at their ophthalmologist or optometrist, by forging
Forgery
Forgery is the process of making, adapting, or imitating objects, statistics, or documents with the intent to deceive. Copies, studio replicas, and reproductions are not considered forgeries, though they may later become forgeries through knowing and willful misrepresentations. Forging money or...
medical prescription
Medical prescription
A prescription is a health-care program implemented by a physician or other medical practitioner in the form of instructions that govern the plan of care for an individual patient. Prescriptions may include orders to be performed by a patient, caretaker, nurse, pharmacist or other therapist....
s or by trying to order it via an online pharmacy
Online pharmacy
Online pharmacies, Internet pharmacies, or Mail Order Pharmacies are pharmacies that operate over the Internet and send the orders to customers.Online or internet pharmacies might include:...
) and secretly use the substance to numb their eye pain, often ending up with irreversible corneal damage or even destruction (which is a vicious cycle and causes even much more pain). Often, such patients finally require corneal transplantation
Cornea transplant
Corneal transplantation, also known as corneal grafting, is a surgical procedure where a damaged or diseased cornea is replaced by donated corneal tissue in its entirety or in part...
.
In case of prolonged or chronic eye pain, especially neuropathic eye pain, it is highly advisable to use centrally
Central nervous system
The central nervous system is the part of the nervous system that integrates the information that it receives from, and coordinates the activity of, all parts of the bodies of bilaterian animals—that is, all multicellular animals except sponges and radially symmetric animals such as jellyfish...
acting substances like anticonvulsants (pregabalin
Pregabalin
Pregabalin is an anticonvulsant drug used for neuropathic pain and as an adjunct therapy for partial seizures with or without secondary generalization in adults. It has also been found effective for generalized anxiety disorder and is approved for this use in the European Union. It was designed...
, gabapentin
Gabapentin
Gabapentin is a pharmaceutical drug, specifically a GABA analogue. It was originally developed for the treatment of epilepsy, and currently is also used to relieve neuropathic pain...
and in more serious cases carbamazepine
Carbamazepine
Carbamazepine is an anticonvulsant and mood-stabilizing drug used primarily in the treatment of epilepsy and bipolar disorder, as well as trigeminal neuralgia...
) or antidepressants (for example SSRIs or the tricyclic antidepressant
Tricyclic antidepressant
Tricyclic antidepressants are heterocyclic chemical compounds used primarily as antidepressants. The TCAs were first discovered in the early 1950s and were subsequently introduced later in the decade; they are named after their chemical structure, which contains three rings of atoms...
amitriptyline
Amitriptyline
Amitriptyline is a tricyclic antidepressant . It is the most widely used TCA and has at least equal efficacy against depression as the newer class of SSRIs...
). Even very small amounts of an anticonvulsant and/or an antidepressant can almost completely stop eye pain and does not damage the eye at all.