Hyoscyamine

Administration

• Type: Anticholinergic
• Dosage Forms: TAB 0.125mg; SL TAB: 0.125mg; INJ: 0.5 mg/mL; Drops 0.125 mg/mL
• Routes of Administration: Oral, sublingual, IM/IV
• Common Trade Names: Levsin

Adult Dosing

GI Tract spasm

• 0.125-0.25 mg PO/SL q4h prn
  • Max: 1.5 mg/day

Bladder spasm

• 0.125-0.25 mg PO/SL q4h prn
  • Max: 1.5 mg/day

IBS, adjunct tx

• 0.125-0.25 mg PO/SL q4h prn
  • Max: 1.5 mg/day

PUD, adjunct tx

• 0.125-0.25 mg PO/SL q4h prn
  • Max: 1.5 mg/day

Parkinson's disease, adjunct tx

• 0.125-0.25 mg PO/SL q4h prn
  • Max: 1.5 mg/day

Biliary colic, adjunct tx

• 0.125-0.25 mg PO/SL q4h prn
  • Max: 1.5 mg/day

Renal colic, adjunct tx

• 0.125-0.25 mg PO/SL q4h prn
  • Max: 1.5 mg/day

Rhinitis

• 0.125-0.25 mg PO/SL q4h prn
  • Max: 1.5 mg/day

Diagnostic procedures

• 0.25-0.5mg SC/IM/IV x1

Anesthesia adjunct

• 5mcg/kg SC/IM/IV x1

Surgery adjunct

• 0.125 mg IV prn

Cholinesterase overdose

• Give 0.3-0.6 mg IV for each 0.5-2 mg neostigmine or physostigmine

Pediatric Dosing

Colic, infantile

• <2 yo, 3.4-4.9 kg
  • 4 drops PO q4h prn
• <2 yo, 5-6.9 kg
  • 5 drops PO q4h prn
• <2 yo, 7-9.9 kg
  • 6 drops PO q4h prn
• <2 yo, >10 kg
  • 8 drops PO q4h prn

Bladder or GI Tract spasm

• 2-11 yo
  • 0.0625-0.125 mg PO/SL q4h prn
• 12+ yo
  • 0.125-0.25 mg PO/SL q4h prn

Anesthesia adjunct

• >2 yo
  • 5 mcg/kg SC/IM/IV x1

Special Populations

• Pregnancy Rating: C
• Lactation risk: Caution advised

Renal Dosing

• Adult: Caution advised
• Pediatric: Caution advised

Hepatic Dosing

• Adult: Caution advised
• Pediatric: Caution advised

Contraindications

• Allergy to class/drug
• Glaucoma
• GI obstruction or ileus
• Intestinal atony in elderly pts
• Ulcerative colitis
• Obstructive uropathy
• Prostatic hypertrophy
• MI
• Unstable cardiovascular status
• Autonomic neuropathy
• Toxic megacolon
• Myasthenia gravis

Adverse Reactions

Serious

• Anaphylaxis
• Heat stroke
• IOP increase
• Psychosis, anticholinergic
• Hallucinations

Common

• Xerostermia
• Dry eyes, blurred vision, mydriasis, cycloplegia
• Urinary retention, constipation, nausea, vomiting
• Confusion, impaired memory, excitement, nervousness
• Tachycardia, palpitations
• Anhidrosis, flushing
• Loss of taste
• Headache, Dizziness
• Ataxia
• Drowsiness, weakness, insomnia
• Fever
• Impotence, lactation suppression
• Urticaria

Pharmacology

• Half-life: 2-3.5 hr (7.5 hr ER form)
• Metabolism: Liver
• Excretion: Urine primarily (30-50% unchanged)

Mechanism of Action

• Antagonizes acetylcholine receptors