Secretin (Monograph)

Drug class: Pancreatic Function
VA class: DX900
Molecular formula: C₁₃₀H₂₂₀N₄₄O₄₁

Medically reviewed by Drugs.com on Nov 21, 2024. Written by ASHP.

Introduction

Secretin is a hormone secreted principally by the duodenal mucosa that is used to aid in the diagnosis of pancreatic exocrine dysfunction or gastrinoma or to facilitate the identification of the ampulla of Vater and accessory papilla during endoscopic retrograde cholangiopancreatography (ERCP).^{1 3 5}

Uses for Secretin

Secretin is used to stimulate pancreatic secretions to aid in the diagnosis of pancreatic exocrine dysfunction or to facilitate the identification of the ampulla of Vater and accessory papilla during endoscopic retrograde cholangiopancreatography (ERCP).¹ Secretin also is used to stimulate gastrin release to aide in the diagnosis of gastrinoma.^{1 3 5}

Pancreatic Dysfunction

Secretin is used to stimulate pancreatic secretions, including bicarbonate, to aid in the diagnosis of pancreatic exocrine dysfunction.¹ Secretin acetate (synthetic porcine secretin) is designated an orphan drug by the US Food and Drug Administration (FDA) for this use.²

The current indication for secretin acetate in the diagnosis of pancreatic exocrine dysfunction is based principally on the results of several small studies that evaluated the efficacy and safety of secretin acetate compared with biologically derived porcine secretin in healthy individuals, in patients with chronic pancreatitis, and in patients with a history of chronic pancreatitis.^{1 3 4} Secretin acetate appears to be as effective as biologically derived porcine secretin for diagnosis of pancreatic exocrine dysfunction.^{1 3 4} Following administration of either form of secretin, peak bicarbonate concentrations exceeded 80 mEq/L in all healthy individuals, as well as in patients with recovery of pancreatic function (as evidenced by currently normal secretin stimulation test results) following a history of chronic pancreatitis, and were less than 80 mEq/L in all patients with ongoing chronic pancreatitis.^{1 3 4 6}

Results from these studies should not be generalized to results of secretin stimulation testing conducted in individual laboratories; however, a volume response of less than 2 mL/kg per hour, peak bicarbonate concentration of less than 80 mEq/L, and a bicarbonate output of less than 0.2 mEq/kg per hour generally are consistent with impaired pancreatic function.¹ Nevertheless, the manufacturer states that clinicians or institutions planning to perform secretin stimulation testing for diagnosis of pancreatic exocrine dysfunction should begin by assessing a sufficient number of healthy individuals (i.e., more than 5) to develop proficiency in proper techniques and to generate normal response ranges for the commonly assessed parameters of pancreatic exocrine response to secretin.¹ (See Dosage and Administration.)

Gastrinoma

Secretin is used to stimulate gastrin secretion to aid in the diagnosis of gastrinoma.^{1 3 5} Secretin acetate (synthetic porcine secretin) is designated an orphan drug by the FDA for this use.²

The current indication for secretin acetate in the diagnosis of gastrinoma is based principally on the results of 2 crossover studies that evaluated efficacy and safety of secretin acetate compared with biologically derived porcine secretin in 8 patients with histologically confirmed gastrinoma.^{1 5} Following administration of either secretin acetate or biologically derived porcine secretin, serum gastrin concentrations increased by more than 110 pg/mL above basal levels in all patients.^{1 5}

Gastrin response is the basis for secretin stimulation testing in patients in whom gastrinoma is strongly suspected.^{1 3 5} An increase in serum gastrin concentration of more than 110 pg/mL above basal levels generally is consistent with the presence of gastrinoma.^{1 5} The manufacturer states that correlation of gastrin response with clinical data and additional diagnostic modalities should be utilized when considering the diagnosis of gastrinoma.^{1 5}

Endoscopic Retrograde Cholangiopancreatography

Secretin is used to stimulate pancreatic secretions to facilitate the identification of the ampulla of Vater and accessory papilla during endoscopic retrograde cholangiopancreatography (ERCP).¹ Secretin acetate (synthetic porcine secretin) is designated an orphan drug by the FDA for this use.²

The current indication for secretin acetate in the identification of the ampulla of Vater and accessory papilla during ERCP to aid in cannulation of the pancreatic ducts is based principally on the results of a randomized, placebo-controlled, crossover study in patients with pancreas divisum undergoing ERCP.¹ In this study, administration of secretin (0.2 mcg/kg) or placebo resulted in 25 of 28 or 1 of 16, respectively, successful cannulations of the minor duct.¹

Secretin Dosage and Administration

Reconstitution and Administration

Secretin acetate is administered by slow IV injection over 1 minute.^{1 6}

Secretin acetate is reconstituted by adding 8 mL of sodium chloride injection to a vial labeled as containing 16 mcg of secretin to yield a final concentration of 2 mcg/mL; the vial should be shaken vigorously to ensure complete dissolution.¹

Secretin acetate solution should be used immediately after reconstitution, and any unused solution should be discarded.¹ Prior to administration, the reconstituted solution of secretin acetate should be inspected visually for particulate matter or discoloration; the solution should be discarded if visible particles or discoloration is evident.¹

General Dosage

Dosage of synthetic porcine secretin (secretin acetate) is expressed by weight (in mcg) in terms of the base; each 0.2 mcg of synthetic porcine secretin is approximately equivalent to 1 clinical unit (CU) of biologic activity.^{1 6} (See Description.)

Before administration of the full dose of secretin acetate, a test dose of 0.2 mcg, administered by IV injection, should be given, followed by observation of the patient for approximately 1 minute.¹ If no acute reaction occurs, the full dose of secretin acetate can be administered.¹

Pancreatic Dysfunction

Secretin is administered as part of a multistep diagnostic procedure that consists of fasting, oral intubation, administration of test and diagnostic doses of secretin, and collection and evaluation of duodenal fluids.^{1 4} For the diagnosis of pancreatic dysfunction, the patient should fast for 12–15 hours.¹ Then, a double-lumen tube is passed through the patient’s mouth; under fluoroscopic guidance, the opening of the proximal lumen of the tube is positioned in the gastric antrum, and the opening of the distal lumen is positioned beyond the papilla of Vater.¹ The positioning of the tube must be confirmed and the tube secured prior to secretin testing.¹ Intermittent negative pressure of 25–40 mm Hg is applied to both lumens and maintained throughout the test.¹ When duodenal contents have a pH of 6 or greater, a baseline sample of duodenal fluid is collected over 10 minutes.¹

For diagnosis of pancreatic exocrine dysfunction, the usual adult dose of secretin is 0.2 mcg/kg administered by slow IV injection over 1 minute.¹

Four samples of duodenal fluid are collected (in periods of 15 minutes each) over the next 60 minutes; the duodenal lumen of the tube is cleared with an injection of air after collection of each sample.¹ Wide variation in volume of individual samples of duodenal fluid may indicate incomplete aspiration.¹ Each sample of duodenal fluid should be chilled and subsequently analyzed for volume and bicarbonate concentration.¹

In general, exocrine pancreatic dysfunction typically associated with chronic pancreatitis is suspected when peak bicarbonate concentration for any sample is less than 80 mEq/L.¹ (See Uses: Pancreatic Dysfunction.)

Gastrinoma

Secretin is administered as part of a multistep diagnostic procedure that consists of fasting, determination of baseline fasting serum gastrin concentrations, administration of test and diagnostic doses of secretin, and collection and evaluation of blood samples.¹ For the diagnosis of gastrinoma, the patient should fast for at least 12 hours prior to beginning the test.¹ To determine baseline serum gastrin concentrations, 2 blood samples should be obtained prior to injection of secretin.¹

For diagnosis of gastrinoma, the usual adult dose is 0.4 mcg/kg administered by slow IV injection over 1 minute.¹

Following administration of secretin acetate, additional blood samples are collected for determination of serum gastrin concentrations at 1, 2, 5, 10, and 30 minutes after injection of the drug.¹

In general, gastrinoma is strongly suspected in patients who have an increase in serum gastrin concentration of more than 110 pg/mL over basal levels on any of the postinjection samples.^{1 5}

Endoscopic Retrograde Cholangiopancreatography

For identification of the ampulla of Vater and accessory papilla during endoscopic retrograde cholangiopancreatography (ERCP) to aid in the cannulation of the pancreatic ducts, the usual dose of secretin is 0.2 mcg/kg administered by slow IV injection over 1 minute.¹ Administration of secretin results in visible secretion of pancreatic fluids from the orifices of these papillae, enabling their identification and facilitating cannulation.¹

Special Populations

No special population dosage recommendations at this time.⁶

Cautions for Secretin

Contraindications

Known hypersensitivity to secretin or any ingredient (e.g., mannitol) in the formulation.⁶

Secretin should not be used in patients with acute pancreatitis until the acute episode has subsided.¹

Warnings/Precautions

Sensitivity Reactions

Hypersensitivity reactions have not been reported to date in over 981 patients receiving secretin acetate.¹ However, because of the potential for an allergic reaction, a test dose 0.2 mcg of secretin should be given prior to administration of the full dose (see Dosage and Administration), and appropriate measures for treatment of a hypersensitivity reaction should be readily available.¹ A test dose is particularly important in patients with a history of atopic allergy and/or asthma.¹

General Precautions

Altered Response

Patients who have undergone vagotomy, patients who are receiving anticholinergics at the time of testing, and patients who have inflammatory bowel disease may be hyporesponsive to secretin stimulation; this does not indicate pancreatic disease.¹ A greater than normal volume response to secretin stimulation, which can mask coexisting pancreatic disease, is occasionally seen in patients with alcoholic or other liver disease.¹

Specific Populations

Pregnancy

Category C.¹

Lactation

It is not known whether porcine secretin is distributed into human milk.¹ Because many drugs are distributed into human milk, caution is advised if secretin is administered in nursing women.¹

Pediatric Use

Safety and efficacy of secretin acetate have not been established in children younger than 16 years of age.^{1 6}

Geriatric Use

No substantial differences in safety and efficacy were observed between geriatric and younger patients in clinical studies; however, the possibility that some older patients may exhibit increased sensitivity to secretin cannot be ruled out.¹

Common Adverse Effects

Adverse effects occurring in 1% or more of patients receiving secretin include nausea,¹ abdominal discomfort,¹ bleeding (secondary to sphincterectomy),^{1 6} decreased blood pressure,¹ flushing,¹ diaphoresis,¹ endoscopic perforation of pancreatic duct,¹ upper GI bleeding (secondary to endoscopic abrasion),¹ abdominal cramps,¹ mild bradycardia,¹ burning in stomach,¹ headache,¹ lightheadedness,¹ transient respiratory distress,¹ bloating,¹ diarrhea,¹ fever,¹ transient low oxygen saturation,¹ urticaria (secondary to contrast material),¹ vomiting,¹ fatigue,¹ hot sensation,¹ hunger pangs,¹ leukocytoplastic vasculitis,¹ numbness/tingling in extremities,¹ pallor,¹ abdominal rash,¹ thready pulse, and possible seizure.¹

Drug Interactions

Anticholinergic Agents

Potential pharmacologic interaction; may result in hyporesponsiveness (i.e., producing false-positive results) in patients undergoing secretin stimulation testing for diagnosis of pancreatic exocrine dysfunction.^{1 6}

Description

Secretin is a naturally occurring hormone secreted principally by the duodenal mucosa in response to the presence of acidic content in the small intestine (resulting from gastric emptying).^{1 3} Commercially available secretin acetate is prepared synthetically and has an amino acid sequence identical to that of naturally occurring porcine secretin, consisting of 27 amino acid residues.^{1 3}

Exogenous secretin probably elicits all the pharmacologic responses usually produced by endogenous secretin.^{3 6} In individuals with normal pancreatic function, secretin increases the volume and bicarbonate content of secreted pancreatic juice by stimulating exocrine pancreatic function.^{1 3} In addition, secretin stimulates gastrin release in patients with gastrinoma; the hormone has no effect on or produces small changes in serum gastrin concentrations in healthy individuals or in patients with peptic ulcer disease.^{1 3 6}

The potency of pure secretin is approximately 5000 clinical units (CU)/mg of peptide and is expressed in terms of mcg/mg.⁶ The purity of secretin acetate or naturally occurring porcine secretin is 99.6 or 60%, respectively;⁶ therefore, the potency of secretin acetate or naturally occurring porcine secretin has been reported to be approximately 5000 or 3000 CU/mg, respectively.¹ As a pure peptide product, dosage of synthetic porcine secretin (secretin acetate) is expressed by weight (in mcg) in terms of the base; each 0.2 mcg of synthetic porcine secretin is approximately equivalent to 1 CU of biologic activity.^{1 3 4}

Following IV administration of 0.4 mcg/kg in healthy individuals, serum secretin concentrations generally decline rapidly (i.e., within 60–90 minutes) to baseline levels.¹ The elimination half-life of secretin is approximately 2.7 minutes.¹

Secretin acetate lyophilized powder for injection should be stored at -20°C.¹

Advice to Patients

Importance of discussing with patients the details of the diagnostic procedure prior to administration of secretin.⁶ Importance of women informing clinicians immediately if they are or plan to become pregnant or to breast-feed.⁶ Importance of patients informing clinicians of existing or contemplated concomitant therapy, including prescription and OTC drugs, as well as concomitant diseases.⁶

Preparations

Excipients in commercially available drug preparations may have clinically important effects in some individuals; consult specific product labeling for details.

Please refer to the ASHP Drug Shortages Resource Center for information on shortages of one or more of these preparations.

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