Introduction
Medications and drugs can affect the pupil in many different ways. The two most important regulators of pupil width are the so-called sympathetic and parasympathetic nervous system. These two are opponents in the body and regulate almost all bodily functions.
Thus, the sympathetic nervous system is activating and makes us ready to flee or fight against danger. When the sympathetic nervous system is activated, the pupils dilate. The parasympathetic nervous system is rather responsible for the calm state and is especially active during digestion.
The parasympathetic action causes the pupils to dilate. All medications and drugs that intervene in this system of sympathetic and parasympathetic nervous system can affect the pupil. Thus, the pupil is either dilated or narrowed, and the pupil usually reacts sluggishly or not at all to light stimuli.
Which drugs make pupils large?
Large pupils (pupil dilation = mydriasis) are caused by a variety of drugs. Ophthalmologists in particular take advantage of this by dilating the pupil for eye examinations. The eye drops usually contain atropine (an active ingredient from belladonna).
In addition, drugs that activate the sympathetic nervous system make the pupil dilate. These include adrenaline, noradrenaline and dobutamine. Antihistamines used for allergic reactions and medications for psychotic attacks can also make pupils dilate.
In particular, poisoning with such medications can lead to dilated and sometimes rigid pupils. Likewise, too high doses of certain medications for depression can make the pupils dilate. These include tricyclic antidepressants such as amytriptillin and imipramine. Drugs that dilate the pupils include cannabinoids (cannabis and hemp), cocaine (crack) and amphetamines (speed, pep, meth, MDMA). Hallucinogens such as psilocybin-containing mushrooms, LSD and DMT can also make the pupils dilate.
What drugs make small pupils?
Small pupils are mainly caused by opioids such as morphine, tilidine, oxycodone and tramadol. These are used in medicine to relieve pain, but can cause the pupils to contract if the dosage is too high. Eye drops are also used to narrow the pupil.
Eye drops containing pilocarbin are used for this purpose. These activate the parasympathetic nervous system and thus cause the pupils to become smaller. Other drugs that address the parasympathetic nerves can also narrow the pupils.
Some medications taken to treat dementia can also cause the pupils to narrow. A small pupil can also be caused by the drug clonidine, which is used in alcohol withdrawal therapy, for example. However, small pupils can also be caused by poisoning with insecticides such as parathion or by an overdose of opioid-containing drugs. Opioid drugs include morphine and oxycodone. Methadone and heroin also act via the opioid receptors and can therefore cause the pupils to contract.
All articles in this series:
