A range of sedative and analgesic agents are used separately or in combination to facilitate endoscopic procedures. See Medications. Commonly used regimens for moderate sedation administered by gastroenterologists are described below.

Benzodiazepines and opioids

Benzodiazepines and opioids are the most widely-used classes of medications in current use for IV endoscopic sedation. Benzodiazepines offer sedation, anxiolysis, and amnesia. The addition of an opioid provides analgesia. Extensive experience with these drugs has shown that they can be effectively titrated by non-anesthesiologists to achieve moderate sedation. 

Standard regimens usually involve the intermeitent administration of alternate bolus doses of each of the two drugs until a desired level of sedation is achieved.  The most frequently employed combination is midazolam with meperidine. Midazolam with fentanyl or midazolam alone are also commonly used. Although diazepem is sometimes used, midazolam is generally preferred by endoscopists because of its shorter duration of action, lack of metabolites, and better amnesiatic properties.  However, midazolam is several times more potent than diazepam and dosing needs to be adjusted accordingly.

Meperidine is more frequently chosen because of its greater synergistic effect with midazolam compared to fentanyl. Drawbacks of meperidine include more nausea and fatigue after eating and the undesirable accumulation of metabolites particularly in patients with renal insufficiency. Fentanyl, however, may produce respiratory depression that persists longer than the analgesic effect. 

A principal advantage of both drug classes is the availability of pharmacological antagonists (naloxone for meperidine and fentanyl;  flumazenil for midazolam and diazepam).  When using these agents in combination, the sedationist should be aware of the risk of a synergistic decrease in heart rate, blood pressure, and respiration which can occur. Dosages should be adjusted downward accordingly especially when being administered to elderly or fragile patients.

Combination propofol

When propofol is combined with other sedatives such a benzodiazepine and an opioid, the desired level of analgesia and amnesia can be achieved with a much smaller dose of propofol than would be used if the drug were administered by itself, therefore reducing the risk of deep sedation. Additionally, smaller bolus doses of propofol can be titrated more precisely and the use of a benzodiazepine and an opioid allows for pharmacologic reversibility using naloxone and flumazenil. 

Other agents
A number of other sedative agents are used for endoscopy either alone or in combination with other drugs regimens. These include: ketamine, nitrous oxide, diphenhydramine, promethazine, and droperidol.  Indications for the use of these agents vary. Some have uses in special populations (e.g. ketamine for pediatric patients; doperidol in difficult-to-sedate patients). Others such as diphenhydramine can be used in combination regimens to enhance sedative effects and reduce associated side effects.

Cohen, LB et al. AGA Institute Review of Endoscopic Sedation, Gastronenterology 2007;133:675-701.

Drossman DA, Shaheen NJ, Grimm IS, eds. Handbook of Gastroenterologic Procedure, 4th ed. Philadelphia, PA: Lippincott Williams & Wilkins, 2005:14

Lightdale CJ, Lightdale JR. Advances in Endoscopy and Endoscopic Sedation. Medscape, 2003. 
Accessed April 22, 2008.

Rex DK. Moderate Sedation for Endoscopy: Sedation Regimens for Non-Anesthesiologists, Ailment Pharmacol Ther. 2006;24(2):163-171
Accessed February 13, 2008.

Rex DK. Sedation for endoscopy. Gastroenterology & Hepatology Annual Review. 2006;1. 
Accessed April 16, 2008.

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