science

Tetryzoline

Tetryzoline is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Tetryzoline rather than just read about it. In short: Tetryzoline (INN), also known as tetrahydrozoline, is a drug used in some over-the-counter eye drops and nasal sprays. Tetryzoline was patented in 1954, and came into medical use in 1959.

Key takeaways

Tetryzoline belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Tetryzoline to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Tetryzoline from memory before moving on to harder problems.

Reference excerpt

Tetryzoline (INN), also known as tetrahydrozoline, is a drug used in some over-the-counter eye drops and nasal sprays. 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. 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 and sneezing. Prolonged intranasal use often causes opposite effects in the form of rebound congestion with effects such as chronic redness, swelling and rhinitis. 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. Respiratory depression, low blood pressure, constricted pupils, hypothermia, brief episodes of high blood pressure, drowsiness, headaches and vomiting may also occur. In serious cases some of these effects may result in circulatory shock. 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. With treatment, death is rare.

Pharmacology

Pharmacodynamics Tetryzoline is an alpha agonist for the alpha-1 and alpha-2 receptors. This action relieves the redness of the eye caused by minor ocular irritants. Moreover, to treat allergic conjunctivitis, tetryzoline can be combined in a solution with antazoline.

Pharmacokinetics In a healthy person, the biological half-life of tetryzoline is approximately 6 hours, and it is excreted in urine, chemically unchanged, 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 hrs, 4 hrs, 8 hrs, and 12 hrs. Within a 24-hour time window, since the last dose of tetryzoline, the blood serum concentration of tetryzoline in the test subjects was 0.068-0.380 ng/mL and the urine concentration was 13–210 ng/mL. Both the blood and the urine levels of tetryzoline reached their maximums approximately 9 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 of imidazoline. It has two enantiomers.

Society and culture

Names Tetryzoline is the International Nonproprietary Name (INN).

Urban legend An urban legend suggests that tetryzoline can cause violent diarrhea if given orally, such as by putting a few drops of Visine 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 woman was charged with murdering her husband by putting eye drops containing tetryzoline in his drinking water. An autopsy found a high concentration of tetryzoline in his body. Tetryzoline has been used as a date rape drug in a number of cases because of its ability to cause dizziness and unconsciousness. In 2018, a 62 year-old woman in Pewaukee, Wisconsin, died in an apparent overdose or suicide involving tetryzoline and other substances; in November 2023 her caregiver was convicted of first-degree murder, following the allegation that her death was caused by a water bottle laced with Visine. In 2019, a North Carolina 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

Illustrations

Worked examples

Example 1 — a first encounter with Tetryzoline

Start with the simplest possible case. Write down what Tetryzoline claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Tetryzoline before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Tetryzoline ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Tetryzoline

In research: Tetryzoline appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Tetryzoline in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Tetryzoline is common in secondary-school and first-year university syllabi. It links to neighbouring topics Alpha1-adrenergic agonists, Alpha2-adrenergic agonists, Imidazolines, so understanding it makes those chapters shorter.
In everyday life: Look for Tetryzoline outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

Ask Teacher Smith questions about this articleOpens your AI tutor with a question about “Tetryzoline” →

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study Tetryzoline in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Tetryzoline means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Tetryzoline out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Tetryzoline in simple terms?

Tetryzoline (INN), also known as tetrahydrozoline, is a drug used in some over-the-counter eye drops and nasal sprays. Tetryzoline was patented in 1954, and came into medical use in 1959.

Why does Tetryzoline matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Tetryzoline?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Tetryzoline.