Hyoscyamine
Mechanism :
Hyoscyamine inhibits specifically the actions of acetylcholine on structures innervated by postganglionic cholinergic nerves and on smooth muscles that respond to acetylcholine but lack cholinergic innervation. These peripheral cholinergic receptors are present in the autonomic effector cells of the smooth muscle, cardiac muscle, the sinoatrial node, the atrioventricular node, and the exocrine glands. It is completely devoid of any action in the autonomic ganglia.
Indication :
- Adjunct therapy in peptic ulcer, irritable bowel syndrome, neurogenic bladder and neurogenic bowel disturbances
- To reduce symptoms of functional intestinal disorders such as those seen in mild dysentery, diverticulitis and acute enterocolitis
- Infant colic
- Drying agent in the relief of symptoms of acute rhinitis
- Poisoning by anticholinesterase agents
Contraindications :
Glaucoma, obstructive uropathy; obstructive disease of the gastrointestinal tract; paralytic ileus; intestinal atony of the elderly or debilitated patients; unstable cardiovascular status in acute hemorrhage; severe ulcerative colitis; toxic megacolon complicating ulcerative colitis; myasthenia gravis.
Dosing :
Dose according to age and weight (kg) using 0.125 mg/mL drops or as tablets:
0.0625-0.125 mg (Maximum dose: 0.75 mg/day), extended release tablets: 0.375 mg.
Oral:Gastrointestinal disorders, colic, bladder spasms:
Children <2 years:
2.3-3.3 kg:
3 drops given orally every four hourly as and when needed;
maximum:
18 drops/24 hours.
3.4-4 kg:
4 drops given orally every four hourly as and when needed;
maximum:
24 drops/24 hours.
5-6 kg:
5 drops given orally every four hourly as and when needed;
maximum:
30 drops/24 hours.
7-9 kg:
6 drops given orally every four hourly as and when needed;
maximum:
36 drops/24 hours.
10-14 kg:
8 drops given orally every four hourly as and when needed;
maximum:
48 drops/24 hours.
>15 kg:
11 drops given orally every four hourly as and when needed;
maximum:
66 drops/24 hours.
Children 2-12 years:
10-19 kg:
0.031-0.033 mg; maximum: 0.75 mg/24 hours.
20-39 kg:
0.0625 mg; maximum: 0.75 mg/24 hours.
40-49 kg:
0.0938 mg; maximum: 0.75 mg/24 hours.
>50 kg:
0.125 mg; maximum: 0.75 mg/24 hours.
Children >12 years:
0.125-0.0.25 mg every 4 hours, maximum 1.5 mg/day.
Adverse Effect :
Dryness of the mouth, weakness, blurred vision, tachycardia, palpitations, mydriasis, headache, cycloplegia, ataxia, nausea and vomiting, urinary hesitancy and retention, increased ocular tension, constipation, loss of taste suppression of lactation, speech disturbance, nervousness, bloated feeling, drowsiness, dizziness, insomnia, impotence, allergic reactions or drug idiosyncrasies, urticaria and other dermal manifestations, and decreased sweating.
Interaction :
Antimuscarinics, Amantadine, Haloperidol, Phenothiazines, MAO Inhibitors, Tricyclic Antidepressants or some Antihistamines: Additive adverse effects.
Antacids: May interfere with the absorption of hyoscyamine. Administer before meals; antacids after meals.
Hepatic Dose :
No dosage adjustments are recommended.