12. Clinical Pharmacology

12.1. Mechanism of Action

The mechanism of action of H.P. Acthar Gel in the treatment of infantile spasms is unknown.

H.P. Acthar Gel and endogenous ACTH stimulate the adrenal cortex to secrete cortisol, corticosterone, aldosterone, and a number of weakly androgenic substances. Prolonged administration of large doses of H.P. Acthar Gel induces hyperplasia and hypertrophy of the adrenal cortex and continuous high output of cortisol, corticosterone and weak androgens. The release of endogenous ACTH is under the influence of the nervous system via the regulatory hormone released from the hypothalamus and by a negative corticosteroid feedback mechanism. Elevated plasma cortisol suppresses ACTH release.

H.P. Acthar Gel is also reported to bind to melanocortin receptors.

The trophic effects of endogenous ACTH and H.P. Acthar Gel on the adrenal cortex are not well understood beyond the fact that they appear to be mediated by cyclic AMP.

ACTH rapidly disappears from the circulation following its intravenous administration; in people, the plasma half-life is about 15 minutes. The pharmacokinetics of H.P. Acthar Gel have not been adequately characterized.

The maximal effects of a trophic hormone on a target organ are achieved when optimal amounts of hormone are acting continuously. Thus, a fixed dose of H.P. Acthar Gel will demonstrate a linear increase in adrenocortical secretion with increasing duration for the infusion.

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Questcor

Indications for Use

H.P. Acthar^® Gel (repository corticotropin injection) is an adrenocorticotropic hormone (ACTH) analogue used for:

Monotherapy treatment of infantile spasms (IS) in infants and children under 2 years of age.
The treatment of exacerbations of multiple sclerosis in adults.
For inducing a diuresis or a remission of proteinuria in the nephrotic syndrome without uremia of the idiopathic type or that due to lupus erythematosus.
The following: rheumatic disorders; collagen diseases; dermatologic diseases; allergic states; ophthalmic diseases and respiratory diseases.

Important Safety Information

Acthar should never be given intravenously. It is contraindicated in patients with scleroderma, osteoporosis, systemic fungal infections, ocular herpes simplex, recent surgery, history of or the presence of a peptic ulcer, congestive heart failure, uncontrolled hypertension, primary adrenocortical insufficiency or adrenocortical hyperfunction or sensitivity to proteins of porcine origin. Acthar is contraindicated in children under 2 years of age with suspected congenital infections. Administration of live or live attenuated vaccines is contraindicated in patients receiving immunosuppressive doses of Acthar.

The adverse effects that may occur with Acthar are related primarily to its steroidogenic effects and are similar to corticosteroids. There may be increased susceptibility to new infection and increased risk of reactivation of latent infections. Adrenal insufficiency may occur after abrupt withdrawal of the drug following prolonged therapy. Cushing’s syndrome, elevated blood pressure, salt and water retention, and hypokalemia may be seen. Masking of symptoms of other underlying disease/disorders may occur. There is a risk of gastrointestinal perforation and bleeding with increased risk of perforation in patients with certain GI disorders. Onset or worsening of euphoria, insomnia, irritability (especially in infants), mood swings, personality changes, depression, and psychosis may occur. Caution should be used when prescribing Acthar to patients with diabetes or myasthenia gravis. Prolonged use may produce cataracts, ocular infections or glaucoma. Use in patients with hypothyroidism or liver cirrhosis may result in an enhanced effect. There may be negative effects on growth and physical development and decreases in bone density.

Specific adverse reactions reported in IS clinical trials in infants and children under 2 years of age included: infection, hypertension, irritability, Cushingoid symptoms, constipation, diarrhea, vomiting, pyrexia, weight gain, increased appetite, decreased appetite, nasal congestion, acne, rash, and cardiac hypertrophy. Convulsions were also reported, but these may actually be occurring because some IS patients progress to other forms of seizures and IS sometimes mask other seizures, which become visible once the clinical spasms from IS resolve. Other adverse reactions in adults and children over 2 years of age included: abdominal distension, anxiety, asthma, chest discomfort, congestive heart failure, dizziness, dyspnea, erythema, fatigue, flushing, headache, hyperhidrosis, hypersensitivity or allergic reactions, injection site pain, muscle weakness, palpitations, peripheral edema, tachycardia, and weakness.

This is a summary only. For a full list of warnings, precautions, and adverse events related to Acthar, please refer to the full Prescribing Information including Medication Guide for the treatment of Infantile Spasms.

H.P. Acthar^® Gel and Questcor^® are registered trademarks of Questcor Pharmaceuticals, Inc.

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12. Clinical Pharmacology

12.1. Mechanism of Action

Questcor

Indications for Use

Important Safety Information