Tetryzoline (also known as tetrahydrozoline) is a drug used in some over-the-counter

eye drop Eye drops or eyedrops are liquid drops applied directly to the surface of the eye usually in small amounts such as a single drop or a few drops. Eye drops usually contain saline to match the salinity of the eye. Drops containing only saline ...

s and

nasal spray Nasal sprays are used to deliver medications locally in the nasal cavities or systemically. They are used locally for conditions such as nasal congestion and allergic rhinitis. In some situations, the nasal delivery route is preferred for syste ...

s. Tetryzoline was patented in 1954, and came into medical use in 1959.

Side effects

Tetryzoline eye drops may cause blurred vision, eye irritation and

dilated pupils Mydriasis is the dilation of the pupil, usually having a non-physiological cause, or sometimes a physiological pupillary response. Non-physiological causes of mydriasis include disease, trauma, or the use of certain types of drugs. Normally, as ...

. Tetryzoline is not suitable for prolonged use as its vasoconstrictive effects within the eye eventually decrease or stop. If tolerance to the drug has developed, ceasing its use may cause a rebound effect and ''increase'' redness of the eyes — ⁠a vasodilatory effect. Intranasal use of tetryzoline may cause transient burning, stinging, or dryness of the

mucosa A mucous membrane or mucosa is a membrane that lines various cavities in the body of an organism and covers the surface of internal organs. It consists of one or more layers of epithelial cells overlying a layer of loose connective tissue. It is ...

and sneezing. Prolonged intranasal use often causes opposite effects in the form of rebound congestion with effects such as chronic redness, swelling and

rhinitis Rhinitis, also known as coryza, is irritation and inflammation of the mucous membrane inside the nose. Common symptoms are a stuffy nose, runny nose, sneezing, and post-nasal drip. The inflammation is caused by viruses, bacteria, irritants o ...

. Prolonged use thus may result in overuse of the drug. In children, it might cause profound sedation.

Overdose

Overdose most often causes

slow heart rate Bradycardia (also sinus bradycardia) is a slow resting heart rate, commonly under 60 beats per minute (BPM) as determined by an electrocardiogram. It is considered to be a normal heart rate during sleep, in young and healthy or elderly adults, a ...

Respiratory depression Hypoventilation (also known as respiratory depression) occurs when ventilation is inadequate (''hypo'' meaning "below") to perform needed respiratory gas exchange. By definition it causes an increased concentration of carbon dioxide (hypercapnia ...

low blood pressure Hypotension is low blood pressure. Blood pressure is the force of blood pushing against the walls of the arteries as the heart pumps out blood. Blood pressure is indicated by two numbers, the systolic blood pressure (the top number) and the dia ...

, constricted pupils,

hypothermia Hypothermia is defined as a body core temperature below in humans. Symptoms depend on the temperature. In mild hypothermia, there is shivering and mental confusion. In moderate hypothermia, shivering stops and confusion increases. In severe h ...

, brief episodes of

high blood pressure Hypertension (HTN or HT), also known as high blood pressure (HBP), is a long-term medical condition in which the blood pressure in the arteries is persistently elevated. High blood pressure usually does not cause symptoms. Long-term high bl ...

, drowsiness, headaches and vomiting may also occur. In serious cases some of these effects may result in

circulatory shock Shock is the state of insufficient blood flow to the tissues of the body as a result of problems with the circulatory system. Initial symptoms of shock may include weakness, fast heart rate, fast breathing, sweating, anxiety, and increased thi ...

. Most often overdoses occur in children who have ingested the drug. There is no antidote for tetryzoline or other similar imidazoline analogue poisoning, but the symptoms can be alleviated and with treatment, death is rare.

Pharmacology

Pharmacodynamics

Tetryzoline is an alpha agonist for the

alpha-1 receptor alpha-1 (α1) adrenergic receptors are G protein-coupled receptors (GPCRs) associated with the Gq heterotrimeric G protein. α1-adrenergic receptors are subdivided into three highly homologous subtypes, i.e., α1A-, α1B-, and α1D-adrenergic ...

. This action relieves the redness of the eye caused by minor ocular irritants. Moreover, to treat

allergic conjunctivitis Allergic conjunctivitis (AC) is inflammation of the conjunctiva (the membrane covering the white part of the eye) due to allergy. Although allergens differ among patients, the most common cause is hay fever. Symptoms consist of redness (mainly due ...

, tetryzoline can be combined in a solution with

antazoline Antazoline is a 1st generation antihistamine with anticholinergic properties used to relieve nasal congestion and in eye drops, usually in combination with naphazoline, to relieve the symptoms of allergic conjunctivitis. To treat allergic conjunc ...

Pharmacokinetics

In a healthy person, the

biological half-life Biological half-life (also known as elimination half-life, pharmacologic half-life) is the time taken for concentration of a biological substance (such as a medication) to decrease from its maximum concentration ( Cmax) to half of Cmax in the bl ...

of tetryzoline is approximately 6.0 hours and is excreted, chemically unchanged, in the urine, at least in part. In one study, 10 people were given two drops of 0.5 mg/ml of tetryzoline eye drops (0.025–0.05 mg) at 0.0 hrs, 4.0 hrs, 8.0 hrs, and 12.0 hrs. Within a 24-hour time window, since the last dose of tetryzoline, the blood serum concentration of tetryzoline in the test subjects was 13.0–210.0 ng/ml and the urine concentration was 11–400 ng/ml. Both the blood and the urine levels of tetryzoline reached their maximums approximately 9.0 hrs after the last dose. These fluid-concentration levels correspond to normal ocular use of tetryzoline; thus, greater concentrations of tetryzoline in the blood and the urine of the user can indicate misuse of the drug or of poisoning with the drug.

Chemistry

Chemically, tetryzoline is a

derivative In mathematics, the derivative of a function of a real variable measures the sensitivity to change of the function value (output value) with respect to a change in its argument (input value). Derivatives are a fundamental tool of calculus. F ...

imidazoline Imidazoline is a class of heterocycles formally derived from imidazoles by the reduction of one of the two double bonds. Three isomers are known, 2-imidazolines, 3-imidazolines, and 4-imidazolines. The 2- and 3-imidazolines contain an imine In ...

. It has two

enantiomers In chemistry, an enantiomer ( /ɪˈnænti.əmər, ɛ-, -oʊ-/ ''ih-NAN-tee-ə-mər''; from Ancient Greek ἐνάντιος ''(enántios)'' 'opposite', and μέρος ''(méros)'' 'part') – also called optical isomer, antipode, or optical anti ...

Society and culture

Names

Tetryzoline is the

INN Inns are generally establishments or buildings where travelers can seek lodging, and usually, food and drink. Inns are typically located in the country or along a highway; before the advent of motorized transportation they also provided accommo ...

Urban legend

urban legend An urban legend (sometimes contemporary legend, modern legend, urban myth, or urban tale) is a genre of folklore comprising stories or fallacious claims circulated as true, especially as having happened to a "friend of a friend" or a family m ...

suggests that tetryzoline can cause violent diarrhea if given orally, such as by putting a few drops of

Visine Visine is a brand of eye drops produced by Johnson & Johnson. Johnson & Johnson acquired Visine, along with Pfizer's entire consumer healthcare portfolio, in December 2006. In some countries it is called Vispring. Visine Original The active i ...

in an unsuspecting person's beverage. However, the actual results of the prank may be worse, varying from severe nausea and vomiting to seizures or a coma. Larger doses can cause death. Diarrhea is not a side effect.

Criminal use

In late August 2018, a

South Carolina )''Animis opibusque parati'' ( for, , Latin, Prepared in mind and resources, links=no) , anthem = " Carolina";" South Carolina On My Mind" , Former = Province of South Carolina , seat = Columbia , LargestCity = Charleston , LargestMetro = ...

woman was charged with murdering her husband by putting eye drops containing tetryzoline in his drinking water. An autopsy found high concentrations of tetryzoline in his body. Tetryzoline has been used as a

date rape drug A date rape drug is any drug that incapacitates another person and renders that person vulnerable to sexual assault, including rape. The substances are associated with date rape because of reported incidents of their use in the context of two pe ...

in a number of cases due to its ability to cause dizziness and unconsciousness. In 2018 an elderly woman in

Pewaukee, Wisconsin Pewaukee is a city in Waukesha County, Wisconsin. The population was 13,195 at the 2010 census. The Village of Pewaukee, which was incorporated out of the town before it incorporated as a city, is surrounded by the city. The name of the city ...

died in an apparent overdose or suicide, however in June 2021 police charged her caregiver with murder, alleging that the death was caused by a water bottle laced with

. In 2019, a

North Carolina North Carolina () is a state in the Southeastern region of the United States. The state is the 28th largest and 9th-most populous of the United States. It is bordered by Virginia to the north, the Atlantic Ocean to the east, Georgia and So ...

paramedic was accused of using Tetryzoline eye drops to cause the death of his wife. The blood sample results showed about 30 - 40 times higher than the therapeutic level of Tetryzoline.

References

{{Adrenergic receptor modulators Alpha-1 adrenergic receptor agonists Alpha-2 adrenergic receptor agonists Imidazolines Tetralins Topical decongestants Vasoconstrictors