A GI cocktail isn’t a single commercial product, so there’s no pre-made drug to select from a formulary. Writing the prescription means specifying each component individually, with exact volumes and instructions for mixing. The standard version combines three ingredients: a liquid antacid, viscous lidocaine, and an anticholinergic.
The Three Standard Components
A typical GI cocktail prescription includes:
- Liquid antacid (Mylanta or Maalox): 30 mL. Contains aluminum hydroxide, magnesium hydroxide, and simethicone. This neutralizes stomach acid on contact.
- Viscous lidocaine 2%: 5 to 15 mL. This numbs the lining of the throat, esophagus, and stomach, providing fast pain relief. The 10 mL dose sits in the middle of common practice; some emergency departments use as little as 5 mL and others go up to 15 mL.
- Donnatal elixir: 10 mL. This anticholinergic blend (containing hyoscyamine, atropine, scopolamine, and phenobarbital) relaxes smooth muscle in the stomach and intestines, easing cramping.
Not every prescriber includes the anticholinergic. Many emergency departments use a simpler two-ingredient version of just antacid plus viscous lidocaine. Some clinicians prefer this approach because Donnatal contains phenobarbital (a controlled substance) and the belladonna alkaloids carry their own side-effect profile.
How to Structure the Prescription
Because the GI cocktail is a compounded mixture, you write each ingredient as a separate line or specify the combination with clear mixing instructions. A common format looks like this:
Rx:
Mylanta (or Maalox) liquid 30 mL
Viscous lidocaine 2% 10 mL
Donnatal elixir 10 mL
Mix together. Patient to swallow entire mixture as a single dose.
If you’re ordering it in an emergency department or hospital setting, the order typically goes into the system as a one-time dose with the components listed and directions to combine at bedside or in pharmacy. For outpatient prescriptions, you would write each component separately since the patient will need to obtain them individually. The antacid is available over the counter, but viscous lidocaine requires a prescription, and Donnatal is a Schedule IV controlled substance due to its phenobarbital content.
Lidocaine Dosing Limits
Viscous lidocaine 2% contains 20 mg of lidocaine per mL. The maximum single dose for a healthy adult should not exceed 4.5 mg per kilogram of body weight, with an absolute ceiling of 300 mg regardless of the patient’s size. At 15 mL, you’re giving 300 mg, which hits that ceiling exactly. For smaller patients or those with liver disease, a lower volume (5 to 10 mL) is safer. Doses should not be repeated more frequently than every three hours, and no more than eight doses should be given in 24 hours.
Patient Instructions
The GI cocktail is swallowed, not spit out. This distinguishes it from “magic mouthwash,” which uses similar ingredients but is swished and expectorated for mouth sores. The goal with a GI cocktail is to coat the esophagus and stomach lining, so the patient drinks the entire mixture. Instruct the patient not to eat or drink for at least 30 minutes afterward, giving the lidocaine and antacid time to work. Most patients notice relief within 5 to 15 minutes as the lidocaine numbs irritated tissue and the antacid buffers acid.
Warn patients that the lidocaine will temporarily numb the throat, which can feel unusual and may affect swallowing. They should avoid hot foods and drinks during this window to prevent accidental burns in tissue they can’t fully feel.
When a GI Cocktail Is Used
GI cocktails are most commonly given in the emergency department for acute upper abdominal pain, heartburn, and dyspepsia. They provide symptomatic relief while workup continues. They’re also used when a clinician suspects gastroesophageal reflux is causing chest pain.
One critical caveat: a positive response to a GI cocktail does not rule out a heart attack. Both cardiac chest pain and esophageal pain can share nearly identical characteristics, including a similar location, quality, and even partial relief from antacids or nitrates. A systematic review of the available clinical trials found no adequately powered study demonstrating that GI cocktail response can reliably exclude a cardiac event. Standard cardiac workup with serial ECGs and blood markers remains necessary for anyone presenting with acute chest pain, even if the cocktail provides relief.
Contraindications to Check
Each ingredient carries its own precautions. The anticholinergic component (Donnatal) is contraindicated in patients with glaucoma, myasthenia gravis, or suspected bowel obstruction. Diarrhea can sometimes be an early sign of incomplete intestinal blockage, and anticholinergics could mask or worsen that situation. Scopolamine should also be avoided in patients experiencing urinary retention.
Calcium-based antacids require caution in patients with kidney disease because of the risk of elevated calcium levels, though the aluminum/magnesium formulas like Mylanta are more commonly used in GI cocktails. For lidocaine, liver impairment slows metabolism and increases the risk of toxicity, so reducing the volume or omitting the lidocaine component may be appropriate in those patients.
Two-Ingredient and Modified Versions
Many prescribers now write a simplified two-component cocktail: 30 mL of liquid antacid mixed with 10 to 15 mL of viscous lidocaine 2%, omitting the Donnatal entirely. This avoids the sedating effect of phenobarbital and the anticholinergic burden, which matters particularly for elderly patients or anyone already taking other medications with anticholinergic properties. In clinical trials, the antacid-plus-lidocaine combination was the most frequently studied formulation, and the anticholinergic is considered optional rather than essential by most current practice patterns.