Do narcotics cause pupils to become smaller?

From the Guidelines

Yes, narcotics typically cause pupils to become smaller, a condition known as miosis. This occurs because opioids stimulate the parasympathetic nervous system, activating the oculomotor nerve, which controls the pupillary sphincter muscle, causing it to contract and reduce pupil size 1. The degree of pupil constriction often correlates with the dose of the narcotic, with higher doses producing more pronounced miosis. Some key points to consider:

• Opioid medications and drugs such as morphine, heroin, oxycodone, hydrocodone, fentanyl, and methadone all produce this characteristic pinpoint pupil effect.
• This pupillary constriction is so reliable that it serves as one of the key clinical signs healthcare providers look for when assessing potential opioid overdose, along with respiratory depression and decreased consciousness.
• In severe overdose cases, pupils may become as small as 1mm in diameter, often described as "pinpoint pupils," and this effect persists even in dark environments where pupils would normally dilate, which is why it's a valuable diagnostic sign 1. Key factors that influence the relationship between narcotics and pupil size include:
• The type and dose of the narcotic
• The individual's overall health and medical history
• The presence of other substances or medications that may interact with the narcotic
• The environment and lighting conditions, although miosis persists even in dark environments 1.

From the FDA Drug Label

Morphine causes miosis, even in total darkness. Fentanyl depresses the respiratory centers, depresses the cough reflex, and constricts the pupils

Yes, narcotics, such as morphine and fentanyl, can cause pupils to become smaller, a condition known as miosis. This effect is a result of the drug's action on the central nervous system 2 3.

From the Research

Narcotics and Pupil Size

• Narcotics, also known as opioids, can cause pupils to become smaller, a condition known as miosis 4.
• The neural pathways responsible for regulating pupil size are well defined, and the mechanisms behind the effects of opioids on the eye have been explored in various studies 4.
• Opioids, such as morphine, have a miotic action on the pupil, which is an easily recognizable and quantifiable effect in humans 4.
• The use of opioids can lead to typical clinical effects, including miosis, respiratory depression, and central nervous system depression 5.
• Fentanyl, a synthetic opioid, is a full agonist at the μ-opioid receptor, leading to miosis and other clinical effects 5.

Clinical Implications

• The opioid system plays a central role in pain control and is a key mediator of hedonic homeostasis, mood, and well-being 6.
• Opioid receptors and opioid agonists are widespread throughout nature, and endogenous opioids mediate complex functions in animals and humans 6.
• The management of patients with established long-term opioid therapy requires an understanding of the basic physiology of opioids and opioid pharmacology 6.