Pharmacology - Peripheral Nervous System Drugs

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Atropine

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Type: Anti-muscarinic Agents

Pharmacology: Selectively block muscarinic receptors of the PNS. - Activity at central and peripheral receptors
Systemically it last 4 hours, locally in the eyes it will last days


Therapeutic Use: Antidote to cholinergic agonist overdose. Previously used to dilate pupils

Notes: Caution with patients who have glaucoma, can cause dangerous rise in intraocular pressure

Adverse Effects: Can cause inhibition of sweating, salivation, and lacrimation. If involved in aerobic activity be aware of hyperthermia. Tachycardia, arrhythmias and dilation of cutaneous vessels can occur at toxic levels. May exacerbate urinary retention, angle closure glaucoma.Be aware of sedation, amnesia, delirium, and hallucinations

Contraindications: Not used much therapeutically due to causing: dry mouth, hyperthermia, blurred vision, itchy eyes, constipation, tachycardia, CNS (restlessness, confusion, delirium)

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Acetylcholine (Miochol-E)

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Type: direct cholinergic agonist

Pharmacology:Muscarinic and Nicotinic activity

Therapeutic Use:- Topical for certain eye surgeries (cataracts)
- Limited use due to little specificity in actions

Adverse Effects:They also stimulate the eccrine sweat glands (sympathetic innervation) because they are muscarinic receptors

Contraindications: Do not use in disease states that could be exacerbated due to cholinergic effects such as asthma and hypotension

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Bethanechol (Urecholine)

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Type: direct cholinergic agonist

Pharmacology: Strong Muscarinic

Therapeutic Use:- Non-obstructive urinary retention
- Severe constipation
- GERD


Notes: Major actions on smooth muscle in bladder and GI

Adverse Effects:-They also stimulate the eccrine sweat glands (sympathetic innervation) because they are muscarinic receptors

Contraindications: Do not use in disease states that could be exacerbated due to cholinergic effects such as asthma and hypotension

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Carbachol


Intraocular Solutions: Carbastat, miostat
Topicals: Isoptocarbochol

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Type: direct cholinergic agonist

Pharmacology:Muscarinic and Nicotinic

Therapeutic Use:Open angle glaucoma

Adverse Effects:-They also stimulate the eccrine sweat glands (sympathetic innervation) because they are muscarinic receptors

Contraindications: Do not use in disease states that could be exacerbated due to cholinergic effects such as asthma and hypotension

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Pilocarpine
(Pilocar, Ocusert, Salagen)

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Type: direct cholinergic agonist

Pharmacology:Primarily Muscarinic

Therapeutic Use:- Glaucoma
- Emergency lowering of intraocular pressure in narrow-angle and wide-angle glaucoma
- Xerostomia


Notes: - Far less potent than others, but will penetrate CNS in therapeutic doses
- Causes CNS disturbances
- Stimulate profuse sweating and salivation

Contraindications: Do not use in disease states that could be exacerbated due to cholinergic effects such as asthma and hypotension

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Physostigmine (Antrilirium)

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Type: Reversible Indirect Cholinergic Agonist

Pharmacology:- Alkaloid, tertiary amine. Can cause CNS stimulation
- Can block autonomic ganglia at high doses

Therapeutic Use:- Treatment of Glaucoma
- Counteract anti-cholinergic drug overdose (atropine)
- Counteract drug overdoses with anticholingergic effects

Notes: Rapid IV administration may cause bradycardia, hypersalivation, and seizures

Adverse Effects:- CNS stimulation, restlessness, irregular pulse, palpitations, hallucinations, muscle twitching, weakness,
- High doses may lead to convulsions, bradycardia, paralysis of skeletal muscle

Contraindications:
Do not use in disease states that could be exacerbated due to cholinergic effects such as asthma and hypotension

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Pyridostigmine

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Type: Reversible Indirect Cholinergic Agonist

Pharmacology:- Synthetic quaternary ammonium compound with limited access to CNS
- Onset 30-45 minwith 3-6 hr duration

Therapeutic Use:- Reversal or nondepolarizing NM block drugs
- Myasthenia gravis

Notes: - Direct effect on skeletal muscle
- May cause rash
- IV should be administered slowly
- Causes fewer serious adverse muscarinic effects than neosigmine

Contraindications:Do not use in disease states that could be exacerbated due to cholinergic effects such as asthma and hypotension

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Neostigmine

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Type: Reversible Indirect Cholinergic Agonist

Pharmacology:- Synthetic quaternary ammonium compound with limited access to CNS
- Onset 20-30 min with 2-4 hr duration

Therapeutic Use:- Reversal or nondepolarizing NM block drugs
- Myasthenia gravis

Notes: - Greater effect on skeletal muscle than physostigmine
- Available orally and IV

Contraindications:
Do not use in disease states that could be exacerbated due to cholinergic effects such as asthma and hypotension

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Edrophonium

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Type: Reversible Indirect Cholinergic Agonist

Pharmacology:- Synthetic quaternary ammonium compound with limited access to CNS
- Onset 30-60 sec with 10 min duration

Therapeutic Use:Diagnosis of Myastheia gravis

Notes: - AE generally short lived

Contraindications:Do not use in disease states that could be exacerbated due to cholinergic effects such as asthma and hypotension

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Ambenonium

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Type: Reversible Indirect Cholinergic Agonist

Pharmacology:- These act by inhibiting AChE
- Stimulate both muscarinic and nicotinic receptors

Therapeutic Use: MG? less clinical use

Notes: Has slightly greater effect on periph skeletal muscles than pyridostigmine
- Reported to cause fewer serious AEs than neostigmine but more than pyridostigmine

Adverse Effects: HA at high doeses

Contraindications:Do not use in disease states that could be exacerbated due to cholinergic effects such as asthma and hypotension

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Echothiophate (Phospoline)

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Type: Irreversible Indirect Cholinergic Agonist

Pharmacology: - Form irreversible covalent bonds with AChE.
- Highly lipid soluble
- Effectively absorbed
- Many developed as nerve agents, insecticides
- Excessive activation of nicotinic receptors causes depolarizing muscular blockade and muscle pralysis

Therapeutic Use:Chronic treatment of open-angle glaucoma

Notes: Onset of action 10-30 min and last 3 days to 4 weeks

Contraindications:Do not use in disease states that could be exacerbated due to cholinergic effects such as asthma and hypotension

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Malathion (ovide)

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Type: Irreversible Indirect Cholinergic Agonist

Pharmacology: Form irreversible covalent bonds with AChE.
- Highly lipid soluble
- Effectively absorbed
- Many developed as nerve agents, insecticides
- Excessive activation of nicotinic receptors causes depolarizing muscular blockade and muscle pralysis

Therapeutic Use:Pesticide & used to treat lice

Contraindications:Do not use in disease states that could be exacerbated due to cholinergic effects such as asthma and hypotension

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Direct Acting Cholinergic Agonists Info

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mimic effect of ACh

Adverse effects: Related to parasympathetic stim.
Also stim M-receptors on eccrine sweat glands (thermoregulation)

Contraindications: Do not use in disease states that could be exacerbated due to cholinergic effects such as asthma (bronchoconstriction & increased mucous production) and cardiac disease (hypotension)

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Direct Acting Cholinergic Agonist Drugs

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Acetylcholine
Bethanechol
Carbachol
Pilocarpine
Nicotine

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Reversible Indirect Acting Cholinergic Agonist Drugs

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Donepezil (Aricept)
Endophonium
Neostigmine
Physostigmine
Pyridostigmine

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Irreversible Indirect Acting Cholinergic Agonist Drugs

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Echothiophate
Isofluorphate