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AtroPen Side Effects

Generic Name: atropine

Note: This page contains information about the side effects of atropine. Some of the dosage forms included on this document may not apply to the brand name AtroPen.

For the Consumer

Applies to atropine: oral tablets, parenteral injection

Side effects include:

Most adverse effects are manifestations of pharmacologic effects at muscarinic-cholinergic receptors and usually are reversible when therapy is discontinued.

Severity and frequency of adverse effects are dose related and individual intolerance varies greatly; adverse effects occasionally may be obviated by a reduction in dosage but this also may eliminate potential therapeutic effects.

Frequent effects include xerostomia (dry mouth), dry skin, blurred vision, cycloplegia, mydriasis, photophobia, anhidrosis, urinary hesitancy and retention, tachycardia, palpitation, xerophthalmia, and constipation, which may appear at therapeutic or subtherapeutic doses. Xerostomia is the dose-limiting effect.

Other common effects include increased ocular tension (especially in patients with angle-closure glaucoma), loss of taste, headache, nervousness, restlessness, drowsiness, weakness, dizziness, flushing, insomnia, nausea, vomiting, bloated feeling, anhidrosis (especially in hot environments), fever, mild to moderate pain at the injection site, loss of libido, and erectile dysfunction (via block of cholinergically mediated vasodilation).

For Healthcare Professionals

Applies to atropine: compounding powder, injectable solution, oral tablet


General side effects have included hyperpyrexia, chest pain, excessive thirst, weakness, syncope, tongue chewing, dehydration, and feeling hot, Other general side effects include "atropine (the active ingredient contained in AtroPen) toxicity" (anticholinergic side effects) which often present as fever, agitation, and dry skin/mucous membranes.[Ref]


Tachycardia has sometimes been preceded by an initial, transient bradycardia after smaller doses (less than 0.4 mg) were given. Atropine has produced sustained AV junctional rhythm in some patients with sinus node dysfunction. Premature ventricular depolarizations or ventricular tachycardia has been rare. Ventricular fibrillation have rarely been associated with the use of atropine (the active ingredient contained in AtroPen) especially in the setting of acute myocardial infarction. Rare cases of low and high grade AV block have been associated with the use of atropine in patients with acute inferior myocardial infarction. Atropine has caused peripheral vasodilation, known as the "atropine flush".

The use of atropine to treat asymptomatic bradyarrhythmias in patients with acute myocardial infarction (MI) is somewhat controversial because (1) it appears that asymptomatic bradycardia is relatively benign, (2) vagolytic drugs may decrease the threshold for ventricular arrhythmias, and (3) animal (dog) data have demonstrated that the use of atropine increases the area of ischemia during MI. Limited human data has agreed with the latter, and have shown that adverse effects in acute MI are related to higher initial and total doses. Patients with two or three vessel coronary artery disease (CAD) appear to be less able to increase nutrient myocardial blood flow in response to atropine-induced cardioacceleration relative to patients without CAD or with less extensive CAD.

While atropine appears to consistently accelerate conduction through the AV node at any dose, atropine may cause SA nodal slowing at lower doses (less than 0.4 mg) and acceleration at higher doses (greater than 4.0 mg), depending on the degree of endogenous parasympathetic activity at the time of drug administration.[Ref]

Cardiovascular side effects have included sinus tachycardia, supraventricular tachycardia, junctional tachycardia, ventricular tachycardia, bradycardia, palpitations, ventricular arrhythmia, ventricular flutter, ventricular fibrillation, atrial arrhythmia, atrial fibrillation, atrial ectopic beats, ventricular premature contractions, bigeminal beats, trigeminal beats, nodal extrasystole, ventricular extrasystole, supraventricular extrasystole, asystole, cardiac syncope, prolongation; of sinus node recovery time, cardiac dilation, left ventricular failure, myocardial infarction, intermittent nodal rhythm, prolonged P wave, shortened PR segment, R on T phenomenon, shortened RT duration, widening and flattening of QRS complex, prolonged QT interval, flattening of T wave, repolarization abnormalities, altered ST-T waves, retrograde conduction, transient, AV dissociation, increased blood pressure, decreased blood pressure, labile blood pressure, and weak or impalpable peripheral pules.[Ref]

Nervous system

If delirium due to atropine (the active ingredient contained in AtroPen) develops and there are no contraindications, many experts recommend the use of 2 mg of physostigmine IM or IV once or twice (as needed) as an effective antidote. Repeated doses may be necessary. Diazepam has been useful for the treatment of convulsions secondary to atropine poisoning.[Ref]

Nervous system side effects have included lethargy, somnolence, and insomnia. Higher doses (10 mg or more) may be associated with ataxia, hallucinations (visual or aural), coma, or seizures (generally tonic clonic), abnormal movements, confusion, stupor dizziness, amnesia, headache, diminished tendon reflexes, hyperreflexia, muscle twitching, opisthotonus, Babinski's reflex/Chaddock's reflex, hypertonia, dysmetria, muscle clonus, sensation of intoxication, difficulty concentration, vertigo and dysarthria. Atropine may be the cause of "intensive care unit delirium" in some cases. The elderly appear to be more prone to the anticholinergic effects of atropine on the CNS.[Ref]


When atropine (the active ingredient contained in AtroPen) is given orally or parenterally, its effects on the eyes are essentially the same as when applied directly to the eye, except that the concentration of drug that reaches the eye after systemic administration is relatively small and the effects accordingly less.[Ref]

Ocular side effects have included mydriasis, blurred vision, pupils poorly reactive to light, photophobia, decrease contrast sensitivity, decreased visual acuity, decreased accommodation, strabismus, heterophoria, cyclophoria, acute angle glaucoma, conjunctivitis, keratoconjunctivitis sicca, blindness, tearing, dry eyes, dry conjunctiva, irritated eyes, crusting of eyelids and blepharitis.[Ref]


Atropine (the active ingredient contained in AtroPen) significantly decreases lower esophageal sphincter pressure for 5 to 60 minutes after injection. Because this can place patients at risk of aspiration, it is used with caution as a preanesthetic medication.[Ref]

Gastrointestinal side effects have included dry mouth and mucous membranes (78% of patients), delayed gastric emptying time, reduced gastric acid secretion, constipation, nausea, abdominal pain, paralytic ileus, decreased bowel sounds, distended abdomen, decreased food absorption, dysphagia, and gastroesophageal reflux.[Ref]


Genitourinary side effects have commonly included dose-related urinary retention (due to anticholinergic effects on the urinary sphincter), and impotence in male patients.[Ref]


Dermatologic side effects have included dry mucous membranes, dry warm skin, flushed skin, oral lesions, dermatitis, petechiae rash, macular rash, papular rash, maculopapular rash, scarlatiniform rash, erythematous rash, sweating/ moist skin, cold skin, cyanosed skin and salivation. Inhibition of exocrine sweat glands has not usually been clinically significant except when perspiration is a major factor in body temperature control.[Ref]


Hypersensitivity side effects have been rare and have included urticaria, eczema, papillary hyperplasia, mucopurulent discharge, eosinophilia, pruritus, edema, hypotension, abdominal pain, tachypnea, nausea and vomiting.[Ref]


Local side effects have included mild to moderate pain at the site of injection.[Ref]


Psychiatric side effects have included agitation, restlessness, delirium, paranoia, anxiety, mental disorders, mania, withdrawn behavior and behavior changes.[Ref]


Immunologic side effects have included anaphylactic reactions.[Ref]


Respiratory side effects have included tachypnea, slow respirations, shallow respirations, breathing difficulty, labored respirations, inspiratory stridor, laryngitis, laryngospasm, pulmonary edema, respiratory failure and subcostal recession.[Ref]


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Not all side effects for AtroPen may be reported. You should always consult a doctor or healthcare professional for medical advice. Side effects can be reported to the FDA here.

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