Pilocarpine: Effects on the eye and dry mouth
Pilocarpine is a naturally occurring alkaloid from the leaves of the South American plant Pilocarpus jaborandi. Pharmacologically, pilocarpine is a direct muscarinic agonist and thus belongs to the classical parasympathomimetic drugs. In Germany, pilocarpine is used in two very different areas of indication: locally as eye drops in certain forms of glaucoma and systemically as a tablet for xerostomia (dry mouth). The historical significance in glaucoma therapy has decreased significantly since the introduction of prostaglandin analogues, but pilocarpine remains valuable in specific indications.
A modern application is pilocarpine ophthalmic solution 1.25 percent (Vuity), which has been approved in the USA since 2022 for the treatment of presbyopia and is being discussed in ophthalmology. This indication is not yet approved in Europe, but can be used off-label. Systemic use with pilocarpine tablets (Salagen) is established in Germany for the treatment of xerostomia after radiation therapy and Sjögren syndrome.
Mechanism of action
Pilocarpine directly activates muscarinic acetylcholine receptors (primarily M3) of the parasympathetic nervous system. Activation leads to cholinergic effects on various target organs. In the eye, pilocarpine causes contraction of the ciliary muscle and the sphincter pupillae muscle. Contraction of the sphincter leads to miosis (pupil constriction), contraction of the ciliary muscle opens the trabecular meshwork area and improves aqueous humor drainage. This results in a reduction of intraocular pressure in glaucoma.
In the exocrine glands (saliva, sweat, tears), muscarinic activation leads to increased secretion. This effect is used systemically to stimulate saliva production in patients with xerostomia, provided that functional glandular tissue is still present. Patients without residual function (for example, after complete gland destruction) do not respond.
Pharmacokinetically, pilocarpine has a systemic half-life of 30 to 75 minutes, and the effect in the eye after local administration lasts 4 to 8 hours. The substance is metabolized hepatically and excreted renally. With local application in the eye, systemic absorption is low, but can become relevant with frequent use, particularly through drainage via the tear ducts into the nasal and pharyngeal area.
Areas of application
- Acute angle-closure glaucoma, intensively before and after iridotomy to lower intraocular pressure and open the anterior chamber angle
- Open-angle glaucoma, today reserved for failure or intolerance of modern antiglaucoma agents such as prostaglandin analogues, beta blockers, carbonic anhydrase inhibitors
- Pigmentary dispersion glaucoma and pseudoexfoliation glaucoma, in specific situations
- Xerostomia after radiation therapy of the head and neck region, orally as a tablet
- Xerostomia in Sjögren syndrome, orally to stimulate residual salivary gland function
- Diagnostic application: pilocarpine iontophoresis in sweat test for suspected cystic fibrosis
- Presbyopia (off-label in Germany), low concentration pilocarpine eye drops induce miosis and thereby increase depth of field
Dosage and administration
Glaucoma eye drops: Pilocarpine 1, 2, or 4 percent, one drop 2 to 4 times daily into the conjunctival sac of the affected eye. For acute angle-closure glaucoma, initial dose is one drop of pilocarpine 2 percent every 5 minutes in the first quarter hour, then every hour until pressure drops.
Xerostomia: Pilocarpine tablets 5 mg, 3 to 4 times daily orally, maximum dose 30 mg per day. Begin with 5 mg three times daily, gradually increase according to tolerance.
Presbyopia (off-label): low dose pilocarpine eye drops 1.25 percent, one drop once daily. Effect onset after 15 to 20 minutes, duration of action approximately 6 hours.
Administration of eye drops: After instillation, briefly press the tear duct to reduce systemic absorption. Remove contact lenses before instillation, replace earliest after 15 minutes.
Oral administration: Tablets with meals to reduce gastrointestinal complaints. Adequate fluid intake.
Renal insufficiency: With systemic administration, caution is advised, consider dose adjustment. Liver insufficiency: Caution in severe impairment.
Side effects
Local in the eye: Burning, eye redness, blurred vision (especially in darkness due to miosis), headache over the eyes due to ciliary muscle spasm, accommodation spasm with myopification. With prolonged use, conjunctival irritation, eyelid eczema, punctate keratopathy. In patients with retinal disease, increased risk of retinal detachment due to vitreous traction.
Systemic after eye drops: With frequent use, rarely possible, symptoms as below.
Systemic (oral or with massive local administration): Sweating (very common), increased salivation, nausea, diarrhea, abdominal cramps, headache, dizziness, tears, nasal discharge, bradycardia, hypotension, bronchospasm, urge to urinate, increased bowel movements.
Acute poisoning with massive overdose: SLUDGE syndrome (Salivation, Lacrimation, Urination, Defecation, GI distress, Emesis), bradycardia, bronchospasm with shortness of breath. The antidote is atropine.
Drug interactions
- Beta blockers: additive bradycardia and hypotension, caution with combination.
- Other cholinergic agents (bethanechol, cholinesterase inhibitors): additive cholinergic effect.
- Anticholinergic agents (atropine, tropicamide, tricyclic antidepressants): antagonistic effect in the eye and systemically.
- Antihypertensive agents: additive hypotension.
- Other glaucoma therapeutics: pharmacodynamic synergy, often combined usefully (beta blockers, prostaglandin analogues, carbonic anhydrase inhibitors).
- Inhaled beta-mimetics: pharmacological antagonists on airways, in asthma pilocarpine can intensify bronchospasm.
Special notes
Pregnancy: Limited data, local application appears compatible with low risk. Systemic use only with strict indication. Breast-feeding: Passage into breast milk unclear, caution advised.
Children: Only in specific indications such as sweat test or childhood glaucoma forms under specialized supervision.
Contraindications: Asthma bronchiale, severe COPD (risk of bronchospasm), Parkinson disease, acute iritis and iridocyclitis, severe bradycardia, severe heart failure.
Before use: Ophthalmological examination with slit lamp, intraocular pressure measurement. With systemic use, cardiovascular and pulmonary history.
During therapy: Regular monitoring of intraocular pressure, checking visual function, accommodation, and tear film stability. With xerostomia, monitor saliva production and tolerance.
Lifestyle: Adequate fluid intake, as increased sweating can lead to dehydration. With glaucoma therapy, regular ophthalmological follow-up checks.
Driving ability: Pilocarpine can impair driving ability through accommodation spasm, miosis, and blurred vision, especially after initial use and in twilight. Do not drive or operate machinery at the beginning of therapy.
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- Atropine, anticholinergic as antagonist
- Neostigmine, cholinesterase inhibitor with cholinergic effect
Frequently asked questions
Why has pilocarpine lost importance in glaucoma therapy?
Pilocarpine eye drops must be used multiple times daily, frequently cause local discomfort, reduce vision especially in darkness, and can trigger accommodation spasms. Modern glaucoma therapeutics such as prostaglandin analogues can be used once daily, are well tolerated, and have a stronger pressure-lowering effect. However, pilocarpine remains indispensable in acute angle-closure glaucoma.
How does pilocarpine work for dry mouth after radiation therapy?
In xerostomia after radiation, salivary glands are often partially destroyed. If residual function is still present, pilocarpine can increase residual production by stimulating muscarinic receptors. The effect occurs 30 to 60 minutes after ingestion. With complete gland destruction, pilocarpine is ineffective and saliva substitutes are the alternative.
Why do you sweat so much on pilocarpine tablets?
Pilocarpine also activates muscarinic receptors of the sweat glands. Increased sweating is therefore a very common side effect of oral therapy. With excessive sweating, the dose can be reduced or distributed, adequate fluid intake is important. If sweating is intolerable, therapy adjustment may be necessary.
Can pilocarpine eye drops permanently change vision?
With short-term use, only reversible effects such as miosis, accommodation spasm, and temporary myopification occur. With long-term use, permanent changes such as iris cysts or fixed miosis can develop. In patients with retinal tears or vitreous traction, pilocarpine increases the risk of retinal detachment.
Sources
- Gelbe Liste, Pilocarpine active ingredient profile
- BfArM, Federal Institute for Drugs and Medical Devices
- German Ophthalmological Society (DOG)
- AWMF, Guidelines on glaucoma and Sjögren syndrome
Legal notices and disclaimer
The information provided on this page is for general information purposes only and does not constitute medical advice, diagnosis, or treatment recommendation. It does not replace the advice of a licensed physician or pharmacist. The use of pilocarpine in glaucoma or xerostomia is carried out under medical supervision with regular monitoring. All information is based on specialist information published at the time of preparation and recognized scientific sources, the current specialist information of the manufacturer is always decisive. Sanoliste assumes no liability for completeness, timeliness, or accuracy of the information presented. In case of medical emergency, call the emergency number 112.