cosyntropin
Cortrosyn

Available forms
Available by prescription only
Injection: 0.25 mg

Indications and dosages
 Diagnostic test of adrenocortical function. Adults and children age 2 and older: 0.25 to 0.75 mg I.M. or I.V. (unless label prohibits I.V. administration) between blood samplings. To administer as I.V. infusion, dilute 0.25 mg in D₅W or normal saline solution, and infuse over 6 hours (40 mcg/hour).
Children younger than age 2: 0.125 mg I.M. or I.V.

Pharmacodynamics
Diagnostic action: Cosyntropin is used to test adrenal function. Drug binds with a specific receptor in the adrenal cell plasma membrane to begin synthesis of its entire spectrum of hormones, one of which is cortisol. In patients with primary adrenocortical insufficiency, cosyntropin doesn’t increase plasma cortisol levels significantly.

Pharmacokinetics
Absorption: Inactivated by the proteolytic enzymes in the GI tract. After I.M. administration, cosyntropin is absorbed rapidly. After rapid I.V. administration in patients with normal adrenocortical function, plasma cortisol levels begin to increase within 5 minutes and double within 15 to 30 minutes. Peak levels begin to decrease in 2 to 4 hours.
Distribution: Not fully understood, but drug is removed rapidly from plasma by many tissues.
Metabolism: Unknown.
Excretion: Probably excreted by the kidneys.

Contraindications and precautions
Contraindicated in patients hypersensitive to drug.

Interactions
Drug-drug. Blood, plasma products: Inactivates cosyntropin. Avoid use together.
Cortisone, estrogens, hydrocortisone: May cause abnormally elevated plasma cortisol levels. Avoid use together.

Adverse reactions
CNS: seizures, dizziness, vertigo, increased intracranial pressure with papilledema, pseudotumor cerebri.
CV: flushing.
EENT: cataracts, glaucoma.
GI: peptic ulcer, pancreatitis, abdominal distention, ulcerative esophagitis, nausea, vomiting.
GU: menstrual irregularities.
Musculoskeletal: fractures, muscle weakness, steroid myopathy, loss of muscle mass, osteoporosis, vertebral compression.
Skin: pruritus; impaired wound healing; thin, fragile skin; petechiae; facial erythema; diaphoresis; ecchymoses; acne; hyperpigmentation; hirsutism.
Other: hypersensitivity reactions, cushingoid symptoms.

Effects on lab test results
• May increase serum glucose and sodium levels. May decrease potassium and calcium levels.

Overdose and treatment
Acute overdose requires no therapy other than symptomatic treatment and supportive care, as appropriate.

Special considerations
• High plasma cortisol levels may be reported erroneously in patients receiving spironolactone, cortisone, or hydrocortisone when fluorometric analysis is used. This doesn’t occur with the radioimmunoassay or competitive protein-binding method. However, therapy can be maintained with prednisone, dexamethasone, or betamethasone because these aren’t detectable by the fluorometric method.
• More cortisol is secreted if dosage is given slowly, not rapidly I.V.
• Cosyntropin is less antigenic than corticotropin and less likely to produce allergic reactions.
• For rapid screening, plasma cortisol levels are determined before and 30 minutes after administration of 0.25 mg I.M. or I.V. injection over 2 minutes. Some clinicians prefer plasma cortisol concentration determinations at 60 minutes after injection of cosyntropin.
• Reconstitute powder by adding 1 ml of normal saline solution to 0.25-mg vial to yield a solution containing 0.25 mg/ml.
• A normal response to cosyntropin includes the following values: The control plasma cortisol level exceeds 5 mcg/100 ml plasma; 30 minutes after the injection, cortisol levels increase by 7 mcg/100 ml above control; 30-minute cortisol levels exceed 18 mcg/100 ml.
Pregnant patients
• It isn’t known if drug can harm a fetus. Only use during pregnancy when clearly needed.
Breast-feeding patients
• It isn’t known if drug is excreted in breast milk. Use cautiously in breast-feeding patients.

Patient education
• Inform patient taking spironolactone, cortisone, hydrocortisone, or estrogen that these drugs may interfere with test results.
• Tell patient to report adverse effects immediately.

Reactions may be common, uncommon, life-threatening, or COMMON AND LIFE THREATENING.
◆ Canada only
◇ Unlabeled clinical use