MOTEX

Indications

• Bradycardia
• Premedication for general anesthesia
• Management of organophosphate poisoning

Dosage

Children: For bradycardia, 20 micrograms/kg IV every 5-10 minutes (max. per dose 2 mg) until adequate response.

Adults: For bradycardia, 0.5 to 1 mg IV, may repeat every 3-5 minutes as needed (max total dose 3 mg). For premedication, 0.5 mg IV 30-60 minutes before anesthesia.

Mechanism of action

Atropine sulfate works by blocking the action of acetylcholine at muscarinic receptors, leading to decreased vagal tone and increased heart rate. It also reduces secretions from glands in the respiratory tract and gastrointestinal tract.

Pharmacodynamics

Atropine has a rapid onset of action, particularly when administered intravenously. Its effects on heart rate can be noted within minutes, while its anti-secretory effects can last for several hours. The drug's half-life varies, but its effects can be prolonged due to its ability to cross the blood-brain barrier.

Pharmacokinetics

Atropine sulfate is well absorbed after parenteral administration. It is metabolized in the liver and excreted primarily via the kidneys. The duration of action typically ranges from 1 to 4 hours, depending on the dose and route of administration.

Adverse effects

• Dizziness
• Photophobia
• Skin reactions
• Tachycardia

Interactions

• Caution with beta-blockers
• May interact with other antimuscarinics

Precautions

• Children under 3 months due to the possible association between cycloplegia and the development of amblyopia
• Monitor for effects on driving and skilled tasks due to increased risk of blurred vision

Pregnancy

Manufacturer advises avoid unless potential benefit outweighs risk-no information available.

Breast-feeding

Manufacturer advises avoid-limited information available.

Storage

Store at room temperature, away from light and moisture.

Formulations

• Eye drops
• Eye ointment

Indications

• Bradycardia
• Pre-anesthetic medication to reduce salivary secretions
• Antidote for organophosphate poisoning
• Pupil dilation for ophthalmic examinations

Dosage

Children: Refer to the BNF for Children for specific dosing recommendations for children.

Adults: Refer to the BNF for specific dosing recommendations based on the condition being treated.

Mechanism of action

Atropine competes with acetylcholine for binding to muscarinic receptors in the parasympathetic nervous system. By blocking these receptors, atropine inhibits the actions of acetylcholine, leading to effects such as increased heart rate, decreased gastrointestinal motility, and reduced secretions from glands such as salivary and sweat glands.

Pharmacodynamics

Atropine exhibits dose-dependent effects, with low doses primarily causing inhibition of secretions and higher doses leading to increased heart rate and decreased gastrointestinal motility. Its antimuscarinic properties can also lead to dilation of the pupils (mydriasis) and paralysis of accommodation (cycloplegia). These effects are useful in various clinical situations, such as managing bradycardia or in ophthalmic examinations.

Pharmacokinetics

Atropine is well-absorbed after administration and has a rapid onset of action. It is distributed widely throughout the body, including the central nervous system. The drug is metabolized primarily in the liver, and its elimination half-life varies, typically ranging from 2 to 4 hours. Atropine is excreted in urine, both as unchanged drug and as metabolites.

Contra-indications

• Hypersensitivity to atropine or any of its components
• Angle-closure glaucoma
• Myasthenia gravis
• Obstructive gastrointestinal disease
• Severe ulcerative colitis
• Tachycardia due to thyrotoxicosis

Adverse effects

• Dry mouth
• Blurred vision
• Increased heart rate
• Urinary retention
• Constipation
• Dizziness
• Confusion
• Hallucinations

Interactions

• clozapine+atropine: Unknown (additive effect)
• antipsychotics, second generation+atropine: Unknown (additive effect)

Precautions

• Use with caution in patients with cardiovascular disease
• Use with caution in elderly patients due to increased sensitivity
• Caution in patients with prostatic hypertrophy

Pregnancy

Atropine should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus. It is classified as a Category C drug.

Breast-feeding

Atropine is excreted in breast milk. Caution should be exercised when administering to nursing mothers.

Storage

Store in a cool, dry place, protected from light. Keep out of reach of children.

Formulations

• Atropine sulfate injection
• Atropine tablets

Indications

• Acute diarrhea
• Chronic diarrhea
• Diarrhea associated with inflammatory bowel disease
• Diarrhea due to colostomy or ileostomy

Dosage

Children: For children aged 2 to 12 years, the dose is generally based on

Adults: The usual adult dose for symptomatic relief of diarrhea is 2.5 to 5 mg taken 3 to 4 times daily, not exceeding 20 mg per day.

Mechanism of action

Diphenoxylate stimulates mu receptors in the gastrointestinal tract, reducing peristalsis and constricting sphincters. This results in decreased gastrointestinal motility and prolonged transit time, allowing for greater absorption of fluids and nutrients. The drug induces segmental contractions in the bowel, enhancing contact between the intestinal contents and the mucosa, which contributes to its antidiarrheal effects. Its metabolism leads to the active metabolite difenoxine, which is primarily responsible for its therapeutic effects.

Pharmacodynamics

Diphenoxylate is classified as an antidiarrheal agent. It works by inhibiting gastrointestinal motility, which decreases the frequency of bowel movements and increases stool consistency. The rapid metabolism of diphenoxylate to its active metabolite, difenoxine, enhances its effectiveness in managing diarrhea. The medication has minimal analgesic activity and is not intended for pain relief.

Pharmacokinetics

Diphenoxylate is rapidly absorbed and extensively metabolized in the body through ester hydrolysis, primarily converting to difenoxine, which is the major active metabolite in the bloodstream. The pharmacokinetic profile indicates that diphenoxylate has a short half-life, necessitating multiple doses for sustained antidiarrheal effect. The drug's effects are primarily observed in the gastrointestinal tract, where it acts locally rather than systemically.

Contra-indications

• Hypersensitivity to diphenoxylate or any component of the formulation
• Diarrhea caused by bacterial enteritis or pseudomembranous colitis
• Severe hepatic impairment
• Acute ulcerative colitis

Adverse effects

• Constipation
• Dizziness
• Drowsiness
• Nausea
• Vomiting
• Dry mouth
• Fatigue
• Euphoria (at high doses)

Interactions

• CNS depressants may enhance sedative effects
• Anticholinergic drugs may increase the risk of adverse effects
• Monoamine oxidase inhibitors (MAOIs) may increase the risk of hypertensive crisis

Precautions

• Caution in patients with a history of substance abuse
• Use with caution in patients with liver disease
• Monitor for signs of dehydration in patients with diarrhea
• Should not be used as the primary treatment for diarrhea in children

Pregnancy

Diphenoxylate should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus. There are no adequate and well-controlled studies in pregnant women.

Breast-feeding

It is not known whether diphenoxylate is excreted in human milk. Caution should be exercised when administering to nursing mothers.

Storage

Store at room temperature, away from excess heat and moisture. Keep out of reach of children.

Formulations

• Diphenoxylate hydrochloride 2.5 mg tablets
• Diphenoxylate hydrochloride with atropine sulfate 2.5 mg/0.025 mg tablets
• Oral solution containing diphenoxylate hydrochloride

Mechanism of action

Diphenoxylate is an opiate receptor agonists that stimulate mu receptors in GI to decrease the peristalsis and constrict the sphincters. Diphenoxylate has a direct effect on circular smooth muscle of the bowel, that conceivably results in segmentation and prolongation of gastrointestinal transit time. The clinical antidiarrheal action of diphenoxylate may thus be a consequence of enhanced segmentation that allows increased contact of the intraluminal contents with the intestinal mucosa. ... HYDROLYSIS OF DIPHENOXYLATE CORRESPONDS TO ACTIVATION, & METABOLITE /DIFENOXINE/ IS RESPONSIBLE FOR MOST IF NOT ALL ANTIDIARRHEAL ACTIVITY ... Limits peristalsis by inhibiting mucosal receptors, which abolishes the local mucosal persistaltic reflex, and by stimulating segmental contraction. /Diphenoxylate hydrochloride with atropine sulfate/ Diphenoxylate acts on smooth muscle of the intestinal tract in a manner similar to that of morphine, inhibiting GI motility and excessive GI propulsion. The drug has little or no analgesic acitvity. Although single doses in the usual therapeutic range produce little or no opiate effect, high doses (40-60 mg) may produce euphoria, suppression of the opiate abstinence syndrome, and physical dependence after chronic administration.

Pharmacodynamics

Diphenoxylate, an antidiarrheal, is effective as adjunctive therapy in the management of diarrhea. Diphenoxylate is rapidly and extensively metabolized in man by ester hydrolysis to diphenoxylic acid (difenoxine), which is biologically active and the major metabolite in the blood.