What is the recommended dosage of a GI (Gastrointestinal) cocktail, including liquid aluminum hydroxide/magnesium hydroxide antacid, Donnatal (anticholinergic), and viscous lidocaine (local anesthetic)?

GI Cocktail Dosage

The standard GI cocktail consists of 30 mL liquid antacid (aluminum/magnesium hydroxide) plus 15 mL of 2% viscous lidocaine, with optional addition of 10 mL Donnatal, though evidence shows Donnatal and lidocaine may not provide additional benefit over antacid alone. 1, 2, 3

Standard Adult Formulation

For adults, the typical GI cocktail dosage is:

• 30 mL liquid antacid (Maalox or equivalent aluminum/magnesium hydroxide preparation) 1, 2, 3
• 15 mL viscous lidocaine 2% (if using lidocaine component) 1, 3
• 10 mL Donnatal (if using anticholinergic component) 1, 2

Critical Lidocaine Safety Limits

The maximum single dose of viscous lidocaine 2% for adults must not exceed 300 mg total (15 mL of 2% solution = 300 mg), with dosing intervals of at least 3 hours between administrations and no more than 8 doses in 24 hours. 4

• The FDA label specifies that lidocaine dosing should not exceed 4.5 mg/kg or 2 mg/lb body weight, with an absolute maximum of 300 mg per dose 4
• Minimum interval between doses is 3 hours 4
• Maximum of 8 doses per 24-hour period 4

Pediatric Considerations

GI cocktails should be used with extreme caution in pediatric patients due to high risk of lidocaine toxicity, and are generally not recommended in children under 3 years of age. 4

• For children over 3 years: maximum lidocaine dose is determined by weight (example: 50 lb child should receive no more than 75-100 mg or 3.7-5 mL of 2% viscous lidocaine) 4
• For infants and children under 3 years: if absolutely necessary, no more than 1.2 mL should be applied with a cotton-tipped applicator, with at least 3 hours between doses and maximum 4 doses in 12 hours 4

Evidence-Based Efficacy Considerations

Important caveat: High-quality evidence suggests that antacid alone may be equally effective as the full "cocktail" formulation:

• A randomized double-blind trial found no statistically significant difference in pain relief between antacid alone (25 mm VAS decrease), antacid + Donnatal (23 mm decrease), and antacid + Donnatal + lidocaine (24 mm decrease) 2
• However, another randomized trial showed significantly greater pain relief with antacid + lidocaine (4.0 cm improvement) compared to antacid alone (0.9 cm improvement, P < 0.0001) 3
• A comparison study found benzocaine and viscous lidocaine equally effective when added to the cocktail, with both groups showing significant improvement (p < 0.001) 1

Given the conflicting evidence and potential for lidocaine toxicity, starting with antacid alone (30 mL) is a reasonable first approach, reserving the addition of lidocaine for refractory symptoms. 2

Administration Technique

• The solution should be swished in the mouth and spit out for oral mucosal symptoms, or gargled and swallowed for pharyngeal/esophageal symptoms 4
• Wait 30 minutes to assess response before considering additional interventions 2, 3
• Document the reason for administration and response to therapy 5

Critical Safety Warnings

Avoid concurrent administration with other local anesthetics or within 4 hours of regional anesthetic blocks to prevent cumulative lidocaine toxicity. 6

• Lidocaine can cause cardiac depression, arrhythmias, seizures, and CNS toxicity at toxic plasma concentrations 6
• Signs of toxicity include tinnitus, tingling tongue/lips, light-headedness, slurred speech, muscle twitching, and loss of consciousness 6
• Many patients receive concurrent medications (narcotics in 58% of cases, nitroglycerin in 23%) which may confound assessment of GI cocktail efficacy 5