Drug and Alcohol - Addiction Recovery

Dilated Pupils: What Drugs Make Pupils Dilate, and What Does it Mean?

What do dilated pupils mean, and why do some blogs make your pupils bigger? Our blog examines this symptom of drug and alcohol use.

What Do Dilated Pupils Mean?

Table of contents

Written by

Brian MooreBrian Moore

Content Writer

Reviewed by

Jeremy ArztJeremy Arzt

Chief Clinical Officer

September 27, 2023

The Forge Recovery Center

Dilated pupils are a common side effect of taking recreational drugs, which can be associated with certain types of drug use. This article will discuss what dilated pupils are, what drugs make the pupil dilate, and what it could mean if your pupils are dilated after using drugs.

What Do Dilated Pupils Mean?

Dilated pupils, also known as mydriasis, are the enlargement of the pupil, a black circular opening in the center of the eye. The iris, the colorful eye component, regulates our pupils' size. While pupil size fluctuates typically in response to variations in light levels, many medicines can also produce large noticeable pupil dilation. 

Understanding how drugs alter pupil size is significant because it can provide information about a person's drug use and may indicate drug intoxication. When medications enter the body, they may interact with the autonomic nervous system, which controls involuntary biological activities such as pupil dilation and constriction. 

Stimulants like amphetamines or cocaine can promote pupil dilation by activating the sympathetic nervous system. Opioids and depressants, such as heroin, can cause pupil constriction or pinpoint pupils by suppressing sympathetic nervous system activity.

For healthcare experts, law enforcement, or addiction specialists, dilated pupils might be an essential diagnostic indicator. They can detect drug intoxication, especially when people are trying to hide their substance consumption. 

However, it is crucial to remember that dilated pupils cannot conclusively prove drug usage because other causes, such as darkness, adrenaline, or certain medical disorders, can also induce pupil enlargement.

Additionally, drug-induced pupil dilation might have visual consequences. Increased pupil size can make the eyes more sensitive to light, resulting in discomfort or glare. People with dilated pupils may also have a hazy vision or difficulty focusing on adjacent things. These visual alterations may have an influence on everyday activities and also overall eye health.

What Drugs Cause Dilated Pupils?

Here's a brief list of drugs that can cause pupil dilation:

  • Stimulants (e.g., amphetamines, cocaine)

  • Hallucinogens (e.g., LSD, psilocybin mushrooms)

  • Opioids (can initially cause dilation before constriction)

  • Anticholinergic drugs (e.g., certain antihistamines, tricyclic antidepressants)

  • Atropine and scopolamine (medications with antispasmodic and anti-motion sickness properties)

  • Some medicated eye drops (used for diagnostic or therapeutic purposes)

Why Do Pupils Dilate? Causes of Dilated Pupils

Drug usage can cause pupil dilation, which is a common physiological reaction. Reasons for dilated pupils are various chemicals that can change pupil size by influencing the autonomic nervous system, which controls involuntary body activities.

Amphetamines, cocaine, and MDMA are stimulants that cause pupil dilation. These chemicals activate the sympathetic nervous system, causing pupil dilation. In addition, the increased release of norepinephrine involved in the fight-or-flight response causes the iris dilator muscle to relax and the pupils to widen.

Pupil dilation can also be caused by hallucinogenic substances such as LSD, psilocybin mushrooms, and mescaline. These drugs have an effect on the serotonin receptors in the brain. This influences the sympathetic nervous system and causes pupil dilation.

As a side effect, various drugs, such as antidepressants and antipsychotics, may produce dilated pupils. This is because these drugs can cause changes in pupil size by affecting neurotransmitters or receptor systems in the brain.

It's worth noting that dilated pupils cannot conclusively indicate drug usage. Other variables that might cause pupil dilation include lighting conditions, emotions, and medical issues. Therefore, a full examination of other signs and symptoms, along with a person's history and context, is required to identify the possible effect of drug use on pupil dilation.

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What Do Dilated Pupils Look Like?

Dilated pupils seem bigger than usual, with the black circular opening in the middle of the eye appearing wider. The size of the pupil varies based on lighting, emotions, and other conditions, but dilated pupils are much bigger than normal pupils. When the pupils dilate, more of the iris may become seen, creating the appearance of bigger black pupils.

One or both eyes may have dilated pupils, too. The size of dilated pupils varies according to the cause and severity of dilation. Dilated pupils may react to changes in light differently than normal-sized pupils, reacting slowly or with delayed constriction.

However, dilated pupils alone cannot offer a definite diagnosis or point to a particular cause.

Sympathomimetic Drugs Dilated Pupils

It is widely acknowledged that sympathomimetic drugs promote pupil dilation. Sympathomimetic drugs are substances that imitate or amplify the actions of the sympathetic nervous system. It is responsible for the "fight-or-flight" response in the autonomic nervous system. Sympathomimetic drugs either stimulate or inhibit the reuptake of specific neurotransmitters. Most notably, norepinephrine and adrenaline have various physiological effects, including pupil dilation.

Adderall, Ritalin, and cocaine are sympathomimetic drugs promoting pupil dilation. They cause the iris dilator muscle to relax and the pupils to expand by increasing the release and inhibiting the absorption of norepinephrine.

Other sympathomimetic drugs that might cause pupil dilation include decongestants, bronchodilators, and weight reduction treatments. These medicines operate on adrenergic receptors in the body, causing the sympathetic nervous system to activate and pupil dilation.

Dilated Pupils: Common Drugs and Their Impact on Pupil Size

Different drugs affect pupil size differently, some producing dilatation and others causing constriction. Understanding how common drugs affect pupil size can help detect drug use or intoxication. Following are a couple of such examples.


Amphetamines, cocaine, and MDMA are all known to produce pupil dilation. These substances activate the sympathetic nervous system, causing enlargement of the pupils.


Pupil dilation can also be caused by LSD, psilocybin mushrooms, & mescaline. Hallucinogens act on serotonin receptors in the brain. They affect the sympathetic nervous system and cause pupils to dilate.


Drugs, such as heroin, morphine, and some prescription painkillers, can cause pupil constriction or pinpoint pupils. These drugs suppress sympathetic nervous system activity, resulting in smaller pupils.


Pupil constriction can also be caused by depressant substances such as benzodiazepines, barbiturates, and alcohol. They reduce pupil size by suppressing the sympathetic nervous system.

Anticholinergic drugs

Certain antihistamines, tricyclic antidepressants, and several anti-nausea medications may cause pupil dilation as a side effect. These drugs inhibit the function of acetylcholine, a neurotransmitter that causes constriction.

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Pupil Dilation as an Indicator of Drug Use

Pupil dilation can serve as an indicator of drug intoxication. Changes in pupil size, especially dilation, might provide important information about a person's drug usage or possible intoxication. When certain drugs enter the body, they can affect the autonomic nervous system, which governs involuntary biological activities such as pupil size. 

Stimulants like amphetamines and cocaine, which activate the sympathetic nervous system, frequently produce pupil dilation. The increased release of norepinephrine causes the iris dilator muscle to relax and the pupils to widen.

When combined with additional indicators of drug usage, such as odd behavior, altered mental state, or physical symptoms, pupil dilation is very valuable as an indicator of drug intoxication. Dilated pupils, for example, along with increased energy, talkativeness, and unpredictable behavior, may indicate stimulant usage.

Healthcare experts, law enforcement officers, and addiction specialists are trained to notice and interpret pupil dilation as part of their evaluation process. This information can be used to establish whether drug usage is a contributing cause to the reported symptoms or behavior.

Potential Risks and Side Effects of Drug-Induced Pupil Dilation

While pupil dilation may not be detrimental in and of itself, it is connected with specific risks and adverse effects. Understanding these potential risks is crucial for those who take drugs or come into contact with someone experiencing drug-induced pupil dilation. Following are some points to consider.

Light Sensitivity

Dilated pupils let more light into the eyes, enhancing sensitivity to light, particularly in well-lit surroundings. This can result in pain, eye strain, and difficulties responding to changes in brightness.

Vision Changes

Drug-induced pupil dilation can impair eyesight briefly. Some people may have cloudy vision, difficulties focusing, or alterations in their visual perception. 

These side effects might impair vision and coordination, thus raising the risk of an accident or injury.

Impaired Night Vision

In low-light settings, dilated pupils can make it challenging to see effectively. This can impact depth perception, peripheral vision, and the ability to travel efficiently at night or in low-light situations.

Eye Health Concerns

Prolonged or excessive pupil dilation can pressure the muscles that govern pupil size, perhaps resulting in ocular tiredness, dryness, or pain. 

Furthermore, medicines that dilate the pupils may have other negative effects on eye health, such as increased intraocular pressure or changes in blood flow to the eyes.

Drug Interactions and Overdose Risks

Other side effects of drugs that produce pupil dilation include increased heart rate, higher blood pressure, and changed mental states. 

Drug interactions or excessive drug use can sometimes lead to serious health complications or overdose.

The Importance of Seeking Medical Attention for Persistent Dilated Pupils

Persistent pupil dilation, in which the pupils stay dilated for a lengthy period for no apparent reason, is a serious sign that requires medical care. Here are some of the reasons why obtaining medical attention is critical in such situations:

Underlying Health Conditions

Pupil dilatation that persists may indicate an underlying medical problem or neurological disease. For example, sustained pupil dilation can be caused by conditions such as Horner's syndrome, Adie's tonic pupil, or specific brain traumas. Seeking medical treatment allows healthcare providers to assess the symptoms in the context of the individual's overall health and perform relevant diagnostic procedures to determine the underlying reason.

Drug-Related Issues

While specific drugs could cause temporary pupil dilatation, prolonged dilation may suggest drug intoxication or severe drug responses. Therefore, it is essential to see a medical professional to rule out drug-related reasons, change prescription doses, or investigate other therapies.

Eye Health Evaluation

Sustained pupil dilatation might indicate a problem with your eyes. In addition, glaucoma, ocular damage, and inflammation can all interfere with the regular functioning of the pupils. Prompt assessment by an eye expert can aid in diagnosing and managing any eye-related issues, preventing vision loss or problems.

Neurological Evaluation

The autonomic nervous system, linked to the brain, controls the pupils. Therefore, pupil dilatation that persists can be an indicator of neurological problems such as brain tumors, strokes, or nerve damage. A timely evaluation by a neurologist can assist in diagnosing and treating any underlying neurological problems.

Overall Health

Seeking medical assistance for prolonged pupil dilation provides for a thorough assessment of a person's health. It ensures that any underlying problems or possible concerns are discovered early, allowing suitable treatment and management strategies to be developed. It also allows you to address any concerns, give support, and reduce anxiety associated with the symptoms.

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When Do Drugs Dilated Pupils Return to Normal?

The time it takes for medication-induced pupil dilation to return to normal might vary depending on many factors, including the drug used, dose, and individual metabolism.

Short-acting medications, such as amphetamines or cocaine, can produce temporary pupil dilatation. However, when the medication is metabolized and removed, the pupils progressively recover to normal size.

Hallucinogens, such as LSD or psilocybin mushrooms, can cause pupil dilation during the drug's peak effects, which might last many hours. Then, as the effects of the medicine wear off, the pupils gradually return to their normal size.

Individual sensitivity and factors such as drug co-administration can vary the duration of drug-induced pupil dilation as well. For example, some medications may contain long-acting metabolites, which might extend the impact on pupil size.

Suppose someone suffers prolonged pupil dilation beyond usual or worries about the length. In that case, seeking medical treatment for a thorough assessment is best.

When To Worry About Dilated Pupils?

Following are the key points about when to be concerned about dilated pupils:

  • Unexplained and persistent dilation

  • Unequal pupil size (anisocoria)

  • Severe or sudden dilation, especially with accompanying symptoms like severe headache, blurred vision, confusion, or loss of consciousness

  • Dilated pupils following eye or head trauma

  • Dilated pupils combined with other concerning symptoms like severe pain, vomiting, seizures, changes in consciousness, or difficulty speaking

Dilated Pupils Aren’t the Worst Thing About Addiction. The Forge Recovery Center Can Help You Live the Life You Deserve

As far as outcomes go, dilated pupils are pretty minor when compared to job loss, prison sentences, destroyed relationships, and fatal overdoses. However, dilated pupils are a sign that many of those things can be in a person’s future.

Drug and alcohol abuse seems hopeless, but it isn’t. With professional help, a person can overcome their addictions and truly live the life they deserve. If you’re worried about your relationship with drugs, reach out to The Forge Recovery Center now. We’ll show you a better way.

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