Name of the Direct Cholinergic Drugs
- Acetylcholine
- Methacholine
- Carbachol
- Bethanechol
- Pilocarpine
1.Acetylcholine
| Acetylcholine |
| Availability powder for injection 20mg |
| Indications and dosages Miosis During Ocular Surgery 0.5-2 mL of 1% solution intraocular instillation during surgery |
Mechanism of Action
Direct-acting parasympathomimetic neurotransmitter; causes contraction of sphincter muscles of the iris, which results in miosis and contraction of ciliary muscle and leads to accomodation spasm
Pharmacokinetics
Onset of action: Rapid
Duration: 6 hr
Contraindications
Hypersensitivity to drug or excipients
Administration
Reconstitute vial with 2 mL supplied diluent to obtain 1% solution; use immediately
Instill gently into anterior chamber of eye with suitable atraumatic cannula
May use 2% pilocarpine or 0.25% physostigmine topically immediately after surgery before application of dressing to maintain miosis
For cataract surgery, instill only after delivery of lens
Cautions
- Use reconstituted solution immediately, aqueous solution unstable
- Instill gently; forceful jet may rupture the hyaloid, cause vitreous loss, or traumatize/perforate iris
- Systemic effects (rare) can cause problems for patients with asthma, acute heart failure, GI spasm, peptic ulcer disease, urinary tract obstruction, acute heart failure, and hyperthyroidism
- Not for gas sterilization, if blister or peelable backing is damaged or broken, sterility of enclosed vial and ampoule cannot be assured, open under aseptic conditions only
- If miosis is to be obtained quickly, anatomical hindrances to miosis, such as anterior or posterior synechiae, must be released, prior to administration of therapy; during cataract surgery, use this drug only after delivery of the lens
- Aqueous solutions of acetylcholine chloride are unstable; prepare solution immediately before use; do not use solution which is not clear and colorless; discard any solution that has not been used
2.Methacholine
| Methacholine |
| Availability Inhalation solution kit Powder for reconstitution and dilution 100mg methacholine powder (amber glass vials) Base solution (contains no methacholine) inhalation solution, ready-to-use Each strength contains 3mL/vial 0.0625mg/mL 0.25mg/mL 1mg/mL 4mg/mL 16mg/mL |
| Indications and dosages Diagnosis of Bronchial Airway Hyperreactivity Administered via nebulization in increasing concentrations solutions using either doubling or quadrupling dosing concentrations |
Mechanism of Action
Cholinergic agonist
Bronchial smooth muscle contains significant parasympathetic (cholinergic) innervation
Methacholine agonizes muscarinic receptors, which eventually induce bronchoconstriction
Contraindications
Hypersensitivity to methacholine or other parasympathomimetic agents; reactions have included rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing
Baseline FEV1 <60% predicted (adults or pediatric patients) or <1.5 L (adults)
Precaution
Administration of methacholine chloride powder for inhalation to patients with epilepsy, cardiovascular disease accompanied by bradycardia, vagotonia, peptic ulcer disease, thyroid disease, urinary tract obstruction or other condition that could be adversely affected by a cholinergic agent should be undertaken only if the physician feels benefit to the individual outweighs the potential risks.
Adverse Reactions
Adverse reactions associated with 153 inhaled methacholine chloride challenges include one occurrence each of headache, throat irritation, Light-headedness and itching.
Methacholine chloride powder for inhalation is to be administered only by inhalation. When administered orally or by injection, methacholine chloride is reported to be associated with nausea and vomiting, substernal pain or pressure, hypotension, fainting and transient complete heart block.
3.Carbachol
| Carbachol |
| Availability intraocular solution 0.01% topical solution 1.5%, 3% |
| Indications and dosages Glaucoma 1-2 gtt instilled into conjunctival sac three times daily |
Mechanism of Action
Stimulates cholinergic receptors in the eye and in turn causes miosis
Pharmacokinetics
Duration: 4-8 hr (reduction in intraocular pressure with ophthalmic instillation); 24hr (intraocular administration)
Onset: miosis: 2-3 min ((intraocular inj); ; 10-20 min (ophthalmic instillation)
Administration
Topical solution: to reduce drainage to nose & throat, apply finger pressure to lacrimal sac following administration, remove excess solution from eye & hand
Intraocular Injection: Withdraw appropriate amount into a sterile disposable syringe through a 0.45-micron filter provided by manufacturer using a 21-gauge needle. Prior to administration, remove attached needle & filter from syringe & replace with a suitable atraumatic cannula for intraocular irrigation. Instillation should be gentle & parallel to the iris face & tangential to the pupil border. Discard unused portions.
Contraindications
- Hypersensitivity
- Acute iritis
- Acute inflammatory disease of the anterior chamber
Cautions
- Use caution in asthma, acute heart failure, corneal abrasion, hyperthyroidism, urinary tract obstruction, Parkinson’s disease, active peptic ulcer, GI spasm
- Does not penetrate cornea readily, benzalkonium chloride is added in some formulations to enhance corneal penetration (Isopto-Carbachol)
- Topical ophthalmic solution produces transient ocular & frontal headache
- Use with caution in patients undergoing general anesthesia
- The vial stopper contains natural rubber (latex) which may cause severe allergic reactions
4.Bethanechol
| Bethanechol |
| Availability Tablet 5mg ,10mg ,25mg ,50mg |
| Indications and dosages Urinary Retention 10-50 mg PO three/four times daily GERD (Off-label) 25 mg PO four times daily |
Mechanism of Action
Stimulates parasympathetic receptors to increase bladder muscle tone, which in turn causes contraction and stimulates micturition
Pharmacokinetics
Onset: 30-60 min
Duration: Up to 6 hr
Absorption: Variable
Contraindications
Hypersensitivity, hyperthyroidism, peptic ulcer, asthma, bradycardia, hypotension, AV conduction defects, CAD vasomotor instability, vagotonia, epilepsy, Parkinsonism, GI of GU obstruction, weak bladder wall, recent urinary bladder surgery, GI resection or anastomosis, spastic GI disturbances, HTN, obstructive pulmonary disease, tartrazine sensitivity
Cautions
Since bethanechol contracts the bladder there is potential for influx infection if the sphincter fails to relax
5.Pilocarpine
| Pilocarpine |
| Availability Tablet 5mg, 7.5mg |
| Indications and dosages Radiation-induced Xerostomia 5 mg PO q8hr; may titrate up to 10 mg PO q8hr; not to exceed 30 mg/day Xerostomia Associated with SjÖgren’s Syndrome 5 mg PO q6hr Hepatic Impairment Mild impairment (Child-Pugh score of 5-6): Dose reduction not necessary |
Mechanism of Action
Cholinergic parasympathomimetic with predominant muscarinic action; increases secretion of exocrine glands (sweat, lacrimal, salivary, intestinal, pancreatic glands, and mucous cells of the respiratory tract may be stimulated
Tone and mobility of gallbladder, biliary duct, and urinary tract may be increased
Pharmacokinetics
- Half-Life: 0.76-1.35 hr
- Onset: 20 min (initial response for xerostomia)
- Duration: 3-5 hr (single dose), >10 hr (multiple dose)
- Peak plasma time: 0.85-1.25 hr
- Bioavailability: High fat meal decreases rate & extent of absorption
- Protein bound: None
Contraindications
Uncontrolled asthma, anterior eye inflammation, any time miosis in undesirable (eg, narrow-angle glaucoma, acute iritis)
Hypersensitivity
REFERENCES
- Robert Kizior, Keith Hodgson, Saunders Nursing Drug handbook,1st edition 2024, Elsevier Publications. ISBN-9780443116070
- McGraw Hill- Drug Handbook, Seventh Edition, 2013, McGraw Hill Education Publications,9780071799430.
- April Hazard, Cynthia Sanoski, Davi’s Drug Guide for Nurses -Sixteenth Edition 2019, FA Davis Company Publications,9780803669451.
- Jones and Bartlet, Pharmacology for Nurses, Second Edition, 2020, Jones and Bartlet Learning Publications, ISBN 9781284141986.
- Nursebro.com, Search – Nursebro
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