What Drugs Cause Dilated Pupils?

dilated pupils

This page's content has been reviewed and fact-checked by a certified addiction therapist and a board-certified physician.

This page's content has been reviewed and fact-checked by a certified addiction therapist and a board-certified physician.

Table of Contents

Dilated pupils, a condition medically referred to as mydriasis, can be caused by various factors, including certain drugs that affect the nervous system.

In this article, we discuss dilated pupils and provide an overview of different drugs that can cause this condition.

Definition of Dilated Pupils (Mydriasis)

Mydriasis refers to the abnormal dilation of the pupils in response to various stimuli, including specific drugs.

In a healthy individual, the size of the pupils is primarily regulated by the iris sphincter muscle, which contracts or relaxes to adjust the amount of light entering the eye.

Dilated pupils occur when the iris sphincter muscle relaxes, allowing more light to enter the eye than is typical.

This dilation can have several consequences, such as increased sensitivity to light, blurred vision, and changes in the appearance of the eyes.

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Overview of Drugs Causing Pupil Dilation

There is a wide range of drugs that can cause pupil dilation due to their effects on the nervous system.

These substances typically fall into several categories, such as stimulants, hallucinogens, and anticholinergic drugs.

In other cases, pupil dilation is an unintended side effect resulting from a drug’s impact on the body’s physiological systems.

In the following sections, we will explore various drugs known to cause dilated pupils, including stimulants like amphetamines, cocaine, and caffeine; hallucinogens like LSD and psilocybin; and other categories of substances that can lead to this condition.

By understanding the various drugs and their effects on the body, we aim to provide a comprehensive guide to the complex relationship between these substances and mydriasis.


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Examples of Different Pupil Sizes

Here are three visual examples illustrating pupils of different sizes. These images provide a comparative reference for understanding the variations in pupil size that may occur under different circumstances. These photos can help you differentiate between various pupil sizes, which can be an essential skill in identifying potential drug use.

Normal Pupil Example
what drugs cause dilated pupils
Dilated Pupil (Mydriasis) Example
Miosis Constricted Pupils Example
Constricted Pupils (Miosis) Example


Stimulants are a class of drugs that increase activity in the central nervous system and can lead to heightened alertness, increased energy, and elevated mood. These substances often cause dilation of the pupils as part of their stimulating effects on the body.


Amphetamines are a group of synthetic stimulants that affect the release and reuptake of neurotransmitters in the brain, including dopamine, norepinephrine, and serotonin. These substances can cause a range of effects, including increased heart rate, elevated blood pressure, and dilated pupils.


Methamphetamine, commonly known as meth or crystal meth, is a powerful and addictive stimulant that has a significant impact on the central nervous system. The drug causes the release of large amounts of dopamine in the brain, which leads to feelings of euphoria, increased energy, and alertness. As part of its stimulating effects on the body, methamphetamine can cause mydriasis, which may be accompanied by other side effects, such as dry mouth, sweating, and rapid heart rate.

MDMA (Ecstasy/Molly)

MDMA, also known as ecstasy or molly, is a synthetic psychoactive drug with both stimulant and hallucinogenic properties. It primarily affects serotonin levels in the brain, which are responsible for regulating mood, appetite, and sleep, among other functions. MDMA can cause significant pupil dilation as a result of its impact on serotonin levels. Other common effects of the drug include feelings of emotional closeness, euphoria, and enhanced sensory perception.


Adderall is a prescription medication commonly used to treat attention deficit hyperactivity disorder (ADHD) and, in some cases, narcolepsy. It contains a combination of amphetamine and dextroamphetamine, which increase the levels of certain neurotransmitters in the brain to improve focus, attention, and impulse control. While Adderall can be beneficial for those with ADHD, it can also cause side effects, including pupil dilation. Other potential side effects include increased heart rate, elevated blood pressure, and dry mouth.


Cocaine is a powerful central nervous system stimulant derived from the leaves of the coca plant. It works by blocking the reuptake of dopamine, norepinephrine, and serotonin in the brain, leading to increased levels of these neurotransmitters and producing feelings of euphoria, increased energy, and heightened alertness. Cocaine can cause mydriasis as part of its stimulating effects on the body. Other side effects include elevated heart rate, increased blood pressure, and constricted blood vessels.

Caffeine (in high doses)

Caffeine is a widely consumed stimulant found in coffee, tea, energy drinks, and various medications. It primarily works by blocking adenosine receptors in the brain, which leads to increased alertness and reduced feelings of fatigue. In moderate amounts, caffeine is generally safe and well-tolerated. However, high doses can cause various side effects, including dilated pupils, elevated heart rate, increased blood pressure, and tremors. The extent of pupil dilation may vary depending on individual sensitivity to caffeine and the dosage consumed.


Hallucinogens are a class of psychoactive substances that can alter perception, thoughts, and emotions by affecting the brain’s serotonin receptors. These drugs often cause dilated pupils as part of their effects on the nervous system.

Lysergic acid diethylamide (LSD)

LSD is a potent hallucinogenic drug derived from the ergot fungus. It primarily affects the serotonin receptors in the brain, leading to altered perceptions, vivid hallucinations, and a distortion of the sense of time. LSD commonly causes dilated pupils, along with other side effects such as elevated body temperature, increased heart rate, and sweating.

Psilocybin (Magic Mushrooms)

Psilocybin is the active compound found in magic mushrooms, a group of fungi that contain hallucinogenic properties. When ingested, psilocybin is converted into psilocin, which acts on serotonin receptors in the brain and produces hallucinogenic effects. Dilated pupils are a common effect of psilocybin, along with other symptoms such as heightened sensory perception, altered thought patterns, and emotional changes.

Mescaline (Peyote)

Mescaline is a naturally occurring psychedelic substance found in the peyote cactus and some other cacti. It affects serotonin and dopamine receptors in the brain, causing hallucinations, altered perceptions, and emotional changes. Mescaline can lead to dilated pupils, along with other side effects such as increased heart rate, elevated blood pressure, and sweating.

DMT (Dimethyltryptamine)

DMT is a powerful, naturally occurring hallucinogenic substance found in certain plants and animals. It is also sometimes synthesized in a laboratory setting. DMT primarily affects serotonin receptors in the brain, leading to intense and vivid hallucinations, altered perceptions, and a distorted sense of time. DMT commonly causes dilated pupils, along with other side effects such as increased heart rate, rapid breathing, and dizziness.

Opiates and Opioids

Opiates and opioids are a class of drugs that act on the opioid receptors in the brain and central nervous system, providing pain relief and producing feelings of relaxation and euphoria. While these substances are known for their constricting effect on the pupils (miosis), they can sometimes lead to dilated pupils under certain circumstances or during the withdrawal process.


Heroin is an illegal and highly addictive opioid derived from morphine, a natural substance extracted from the seed pods of opium poppy plants. It is a powerful analgesic and can induce a state of intense relaxation and euphoria. Although heroin typically causes pinpoint pupils (miosis), dilated pupils can occur during withdrawal or as a result of an overdose, which can lead to a range of severe health consequences, including respiratory failure and death.


Morphine is a naturally occurring opiate derived from the opium poppy plant and is used medically for severe pain relief. Like other opioids, morphine primarily causes miosis as a side effect. However, in cases of overdose or withdrawal, the pupils may become dilated. Other side effects of morphine include drowsiness, constipation, and respiratory depression.


Oxycodone is a semi-synthetic opioid derived from thebaine, an alkaloid found in the opium poppy plant. It is used medically for managing moderate to severe pain. Similar to other opioids, oxycodone typically causes miosis, but dilated pupils can be observed during withdrawal or in cases of overdose. Common side effects of oxycodone include dizziness, nausea, and respiratory depression.


Fentanyl is a synthetic opioid that is 50 to 100 times more potent than morphine. It is used medically for severe pain management, often in the form of patches or intravenous administration. Fentanyl generally causes miosis, but dilated pupils can be a sign of overdose or withdrawal. Due to its potency, fentanyl overdose can be life-threatening and requires immediate medical attention. Other side effects of fentanyl include drowsiness, nausea, and respiratory depression.

Summary of Drugs Causing Dilated Pupils

Throughout this article, we have explored various drugs that can cause dilated pupils, also known as mydriasis. These substances include stimulants like amphetamines, cocaine, and caffeine; hallucinogens such as LSD, psilocybin, mescaline, and DMT; and opioids like heroin, morphine, oxycodone, and fentanyl in cases of overdose or withdrawal. It is important to recognize that the extent of pupil dilation and the specific side effects experienced may vary depending on factors such as the type of drug, dosage, individual sensitivity, and duration of use.

Navigating Suspected Drug Use

If you encounter someone you know exhibiting dilated pupils and suspect they may be under the influence of drugs, it’s essential to approach the situation carefully and with empathy. Your response can play a crucial role in helping them seek help, support their well-being, and possibly prevent more severe consequences. Here are some steps to consider when you find yourself in this situation.


Observe and assess the situation

Before jumping to conclusions, take a moment to observe the individual’s behavior and other signs that might indicate drug use. In addition to dilated pupils, look for symptoms such as slurred speech, unsteady gait, erratic behavior, or changes in their normal demeanor.


Approach with care and empathy

If you decide to address your concerns, approach the person with empathy and choose your words carefully. Find a private and comfortable place to talk and ensure you’re in a calm and non-confrontational state of mind.

Avoid accusing them or making assumptions about their drug use; instead, express your concern for their well-being and ask open-ended questions to encourage them to share their experience.


Offer support and resources

If the individual admits to using drugs, offer your support and help them explore the available resources.

Encourage them to seek professional help or connect them with local support groups, mental health services, or addiction treatment programs.

Offer to accompany them to appointments or meetings if they feel comfortable with your assistance.

Recognize the limitations of your role

It’s essential to understand that you cannot force someone to change their behavior or seek help if they are not ready.

You can provide support, information, and encouragement, but ultimately, the decision to address their drug use is up to them.

Be prepared to accept that you might not be able to change their situation and know that your role is limited.

Monitor the situation and prioritize safety

If you believe the individual may be in immediate danger due to their drug use or suspect an overdose, do not hesitate to call emergency services.

Signs of a potential overdose may include extreme drowsiness, difficulty breathing, seizures, or loss of consciousness. In these cases, prompt medical attention is critical.

Maintain communication and follow up

After your initial conversation, continue to check in with the person and offer your support.

Keep an open line of communication and be available to listen, provide encouragement, and share resources when needed. Remember that recovery is a long process and often requires ongoing support from friends and family.

Published: 4/12/2023

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Susana is a recovery writer and advocate with over 8 years in addiction recovery. She is passionate about sharing accurate and helpful information about mental health, addiction, and recovery. She holds a Bachelor’s in Christian Studies from Grand Canyon University and has over 7 years of working in the addiction field. 

lionel estrada lisac clinical director


Lionel, a Licensed Independent Substance Abuse Counselor (LISAC) with over 4 years at Cornerstone. Passionate about helping those with addiction, he has trained as an EMDR therapist  adopting a trauma-informed approach to treat the underlying issues of addiction, providing an empathetic approach to addiction.

Articles written prior to August 2023 were also clinically reviewed by Karen Williams, LPC 

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