Lonox Side Effects

Generic Name: atropine / diphenoxylate

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

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

For the Consumer

Applies to atropine / diphenoxylate: oral solution, oral tablet

In addition to its needed effects, some unwanted effects may be caused by atropine / diphenoxylate. In the event that any of these side effects do occur, they may require medical attention.

You should check with your doctor immediately if any of these side effects occur when taking atropine / diphenoxylate:

  • Bloating
  • constipation
  • loss of appetite
  • stomach pain (severe) with nausea and vomiting

You should check with your doctor immediately if any of these side effects occur when taking atropine / diphenoxylate:

  • Blurred vision (continuing) or changes in near vision
  • drowsiness (severe)
  • dryness of mouth, nose, and throat (severe)
  • fast heartbeat
  • shortness of breath or troubled breathing (severe)
  • unusual excitement, nervousness, restlessness, or irritability
  • unusual warmth, dryness, and flushing of the skin

Some of the side effects that can occur with atropine / diphenoxylate may not need medical attention. As your body adjusts to the medicine during treatment these side effects may go away. Your health care professional may also be able to tell you about ways to reduce or prevent some of these side effects. If any of the following side effects continue, are bothersome or if you have any questions about them, check with your health care professional:

Less common or rare
  • Blurred vision
  • confusion
  • difficult urination
  • dizziness or light-headedness
  • drowsiness
  • dryness of skin and mouth
  • fever
  • headache
  • increased body temperature
  • mental depression
  • numbness of hands or feet
  • skin rash or itching
  • swelling of the gums

After you stop taking this drug, it is possible that you may still experience side effects that need medical attention. If you notice any of the following side effects check with your doctor immediately:

  • Increased sweating
  • muscle cramps
  • nausea or vomiting
  • shivering or trembling
  • stomach cramps

For Healthcare Professionals

Applies to atropine / diphenoxylate: oral liquid, oral tablet

Nervous system

Central nervous system or respiratory depression due to this drug requires immediate medical attention. Opioid symptoms can be reversed by administering naloxone, but artificial respiration may be necessary. Gut decontamination (if the ingestion is recent and the patient is alert), emergency equipment, and monitoring are recommended.

Nervous system side effects have usually indicated toxicity. Toxicity of this drug can be fatal. Toxicity has been described as "biphasic". Early signs are related to atropinism (fever, hypertension, flushed/dry skin, mydriasis, tachycardia, tachypnea, disorientation/hallucinations), while late signs are related to opioid toxicity (lethargy, somnolence, hypotonic reflexes, respiratory depression, miosis, coma). The early phase usually lasts for 2 to 3 hours. The late phase usually follows immediately, but can be delayed for as long as 36 hours.

Children are particularly sensitive to atropinism, which has been reported in young children after a single atropine-containing eye drop.

The elderly appear to be more prone to the anticholinergic effects of atropine on the CNS.

Nervous system side effects have also included drowsiness/sedation, numbness of extremities, euphoria, depression, malaise/lethargy, confusion, dizziness, restlessness, and headache.


Because this drug inhibits gastrointestinal peristaltic activity, it can prolong and/or worsen diarrheas associated with some pathogens (toxigenic E. coli, Salmonella, and Shigella) and pseudomembranous enterocolitis associated with some antimicrobial agents. In these cases, diarrhea may represent a defense mechanism when disease is caused by a bacterial pathogen that must penetrate the intestinal epithelium to produce illness. Increased intestinal motility may decrease contact time between the invasive bacteria and mucosal cells.

Atropine's anticholinergic effects have included dry mouth and mucous membranes, delayed gastric emptying time, reduced gastric acid secretion, constipation, and gastroesophageal reflux.

Atropine-diphenoxylate can induce paralytic ileus and has been associated with the development of toxic megacolon in some patients with acute ulcerative colitis. While abdominal distension has been reported in 6% of all patients, abdominal pain in patients with ulcerative colitis usually indicates discontinuation of therapy.

Total fluid requirements may be significantly increased during therapy due to decreased bowel motility and fluid absorption.

Rare cases of pancreatitis have been associated with diphenoxylate.

As an opioid derivative, diphenoxylate may cause spasm of the sphincter of Oddi.

Gastrointestinal side effects have included inhibition of gastrointestinal peristaltic activity possibly resulting in prolonged or worsening diarrhea, inducement of paralytic ileus possibly resulting in toxic megacolon, abdominal distention, abdominal pain, spasm of the sphincter of Oddi, nausea, vomiting, and anorexia. Other gastrointestinal side effects have included dry mouth and mucous membranes, delayed gastric emptying time, reduced gastric acid secretion, constipation, and gastroesophageal reflux. Pancreatitis has been reported rarely.


While muscarinic blockade due to atropine can result in tachycardia or, after higher dosages, sustained AV junctional rhythm, premature ventricular depolarizations or ventricular tachycardia, arrhythmias are rare because of the miniscule dose of atropine in the combination drug.

Cardiovascular side effects have rarely included cardiovascular collapse, or arrhythmias.


Ocular side effects have included pinpoint pupils, inhibition of the iris sphincter muscle, and inhibition of the ciliary muscle. A single case of keratoconjunctivitis sicca has been reported.

Pinpoint pupils have been reported as a possible result of the opioid activity of diphenoxylate

The anticholinergic activity of atropine has been known to cause inhibition of the iris sphincter muscle (possibly resulting in dilation of the pupil) and inhibition of the ciliary muscle (which can interfere with near vision in up to 23% of patients)

A 47-year-old man with refractory diarrhea who was taking 10 to 30 tablets of atropine-diphenoxylate every day (0.25 to 0.75 mg and 25 to 75 mg, respectively) developed ocular irritation, burning, photophobia, and local erythema. Examination revealed a decreased tear meniscus and punctate epithelial keratopathy. Use of artificial tears was unsuccessful. Vitamin A levels were normal. The patient's signs and symptoms resolved when atropine was selectively withheld, and were reproducible when atropine was added to diphenoxylate.


Genitourinary side effects have included impotence in male patients and urinary retention in all treated patients.

Urinary retention experienced with atropine-diphenoxylate therapy has been associated with the anticholinergic effects on the detrusor muscle.


Psychiatric side effects have included psychiatric and physiologic addiction or abuse.

Psychiatric and physiologic addiction to or abuse of diphenoxylate has been reported. The addition of atropine is meant to discourage deliberate overdosage.


The only usual dermatologic side effect from atropine is inhibition of exocrine sweat glands and dry skin. This problem is usually not clinically significant except when perspiration becomes a major factor in body temperature control.

Dermatologic side effects have rarely included inhibition of exocrine sweat glands and dry skin.


Hypersensitivity side effects have included urticaria, pruritus, angioneurotic edema, hypotension, abdominal pain, tachypnea, swelling of the gums, nausea and vomiting. Systemic hypersensitivity reactions to either diphenoxylate or atropine have occurred rarely.


Extremely rare cases of hyperglycemia have been associated with atropine-diphenoxylate overdosage. The mechanism is not known, but is suspected to be increased sympathetic activity due to atropine toxicity.

Metabolic side effects have rarely included hyperglycemia.

Disclaimer: Every effort has been made to ensure that the information provided is accurate, up-to-date and complete, but no guarantee is made to that effect. In addition, the drug information contained herein may be time sensitive and should not be utilized as a reference resource beyond the date hereof. This material does not endorse drugs, diagnose patients, or recommend therapy. This information is a reference resource designed as supplement to, and not a substitute for, the expertise, skill , knowledge, and judgement of healthcare practitioners in patient care. The absence of a warning for a given drug or combination thereof in no way should be construed to indicate safety, effectiveness, or appropriateness for any given patient. Drugs.com does not assume any responsibility for any aspect of healthcare administered with the aid of materials provided. The information contained herein is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. If you have questions about the substances you are taking, check with your doctor, nurse, or pharmacist.