Stiefotrex

Uses

Stiefotrex is used for the treatment of severe recalcitrant nodular acne. Nodules are inflammatory lesions with a diameter of 5 mm or greater. The nodules may become suppurative or hemorrhagic. Because of significant adverse effects associated with its use, Stiefotrex should be reserved for patients with severe nodular acne who are unresponsive to conventional therapy, including systemic antibiotics. In addition, Stiefotrex is used only for those female patients who are not pregnant, because Stiefotrex can cause severe birth defects.

A single course of therapy for 15 to 20 weeks has been shown to result in complete and prolonged remission of disease in many patients. If a second course of therapy is needed, it should not be initiated until at least 8 weeks after completion of the first course, because experience has shown that patients may continue to improve while off Stiefotrex . The optimal interval before re-treatment has not been defined for patients who have not completed skeletal growth

Stiefotrex is also used to associated treatment for these conditions: Acne Rosacea, Acne conglobata, Mycosis Fungoides (MF), Neuroblastomas, Sezary Syndrome, Refractory Acne vulgaris, Severe Recalcitrant nodular acne

How Stiefotrex works

Stiefotrex produces its effects through altering progress through the cell cycle, cell differentiation, survival, and apoptosis. These actions reduce sebum production, preventing the blockage of pores, and growth of acne causing bacteria. Stiefotrex and 4-oxo-isotretinoin both significantly reduce the production of sebum. Stiefotrex has little to no affinity for retinol binding proteins (RBPs) and retinoic acid nuclear receptors (RARs). Tretinoin and 4-oxo-tretinion bind to the RAR-γ receptor, which is suspected to be part of the action of acne treatment by isotretinoin. Stiefotrex induces apoptosis in sebocytes, leading to a decrease in sebum production. Stiefotrex also reduces the formation of comedones by reducing hyperkeratinization through an unknown mechanism. Stiefotrex does not directly kill bacteria but it does reduce the size of sebum ducts and makes the microenvironment less hospitable to acne causing bacteria. It may also increase immune mechanisms and alter chemotaxis of monocytes to reduce inflammation.

There is preliminary evidence suggesting isotretinoin may interact with FoxO1, which may explain a substantial number of isotretinoin's unexplained actions.

Dosage

Stiefotrex dosage

Oral-

• Adult: Initially, 0.5 mg/kg daily in single or 2 divided doses, increased to 1 mg/kg daily if necessary. Usual duration of treatment: 16-24 wk. May repeat treatment course after at least 8 wk if relapse after first course.
• Child: ≥12 yr Same as adult dose.

Topical:Apply Stiefotrex 0.05% gel cautiously over the affected area once or twice daily.Patients should be advised that 6-8 weeks of treatment may be required before a therapeuticeffect is observed. The safety and efficacy of Stiefotrex have not been established in children since acne vulgarisrarely present in this age group. There are no specific recommendations for use in the elderly.Acne vulgaris does not present in the elderly.

Side Effects

Erythema, skin exfoliation, stinging sensation, pruritus, irritation, tenderness, dry skin, hirsutism, photosensitivity, skin pigmentation, paronychia, nail dystrophy, pyogenic granuloma, increased sweating, corneal opacities, visual disturbances, headache, nausea and vomiting, arthralgia, myalgia, back pain, intracranial HTN, hyperostosis and calcinosis. Elevation of serum triglycerides, LFTs, ESR and blood glucose. Mood changes, psychotic symptoms, depression and suicidal behaviour.

Toxicity

Patients experiencing an overdose may present with vomiting, facial flushing, cheilosis, abdominal pain, headache, dizziness, and ataxia. These symptoms may rapidly resolve. Generally no treatment is required for these overdoses.

The oral lowest dose causing toxic effect (TDLO) for children is 30mg/kg/21W, oral TDLO for men is 24mg/kg/4W, oral TDLO for women is 56mg/kg/8W. The intraperitoneal LD₅₀ for rats is 901mg/kg, oral LD₅₀ for mice is 3389mg/kg, oral LD₅₀ for rats is >4000mg/kg.

Stiefotrex is associated with major congenital malformations, spontaneous abortion, and premature birth. It is unknown if isotretinoin is expressed in breast milk but due to the associated hazards a decision should be made to either stop nursing or stop taking isotretinoin.

In animal studies, isotretinoin was associated with an increased risk of pheochromocytoma and adrenal medullary hyperplasia at doses above the recommended clinical dose. Stiefotrex was negative for the Ames test of mutagenicity once and weakly positive a second time. It has not been shown to be clastogenic. A study in dogs noted testicular atrophy after doses of 10-30 times the recommended clinical dose for 30 weeks. In trials with men there were no effects seen on sperm count, motility, morphology, ejaculate volume, and seminal plasma fructose.

Precaution

Women of childbearing potential; anorexia nervosa. History of photoallergy, psychiatric disorder (e.g. depression); pre-existing or predisposition to hypertriglyceridaemia (e.g. DM, obesity or increased alcohol intake). Genetic predisposition for age-related osteoporosis, history of childhood osteoporosis, osteomalacia or other bone metabolism disorders. Not intended for the treatment of prepubertal acne. Severe renal impairment.

Interaction

Additive adverse effects with vit A or its derivatives. Decreased efficacy of microdosed progesterone (use 2 forms of contraception).Increased risk of local irritation with topical keratolytic or exfoliative anti-acne agents. Oxidising agents (e.g. benzoyl peroxide) may reduce the efficacy of topical isotretinoin.

Food Interaction

• Avoid alcohol. Alcohol with isotretinoin can lead to inflammation of the liver.
• Avoid vitamin A supplements.
• Take with food. High-fat food increases drug absorption.

Stiefotrex Alcohol interaction

[Moderate] GENERALLY AVOID:

The combined use of ethanol and isotretinoin may result in a disulfiram-like reaction.

The mechanism has not been established.

Alcohol consumption should be avoided during isotretinoin therapy.

Stiefotrex Cholesterol interaction

[Moderate] The use of retinoids is associated with elevations in serum triglycerides and cholesterol, and decreases in HDL.

In addition to cardiovascular risks, elevation of serum triglycerides to greater than 800 mg

Patients at increased risk for developing hypertriglyceridemia during retinoid therapy include those with diabetes mellitus, obesity, high alcohol consumption, or a family history of these conditions.

Blood lipid determinations should be performed prior to initiation of therapy and at 1- to 2- week intervals until the lipid response to the drug is established (usually 4 to 8 weeks).

Patients with preexisting hyperlipidemia may require closer monitoring during retinoid therapy, and adjustments made accordingly in their lipid-lowering regimen.

Stiefotrex Drug Interaction

Unknown: amphetamine / dextroamphetamine, amphetamine / dextroamphetamine, amphetamine / dextroamphetamine, amphetamine / dextroamphetamine, acetaminophen, acetaminophen, cyanocobalamin, cyanocobalamin, ascorbic acid, ascorbic acid, cholecalciferol, cholecalciferol, lisdexamfetamine, lisdexamfetamine, bupropion, bupropion, alprazolam, alprazolam, cetirizine, cetirizine

Stiefotrex Disease Interaction

Major: intracranial hypertension, psychiatric disordersModerate: osteoporosis, elevated serum triglycerides, liver disease

Volume of Distribution

The volume of distribution in humans is unknown because there is no intravenous preparation. In a study of pediatric patients with neuroblastoma the volume of distribution was found to be 85L. The volume of distribution was also found to be 2432mL/kg in guinea pigs and 1716mL/kg in obese rats.

Elimination Route

Patients reach a maximum concentration of 74-511ng/mL after 1-4 hours following a 100mg oral dose. Stiefotrex is better absorbed with a high fat meal and bioavailability may change from one brand to another.

Following a 40mg oral dose, fasted subjects reached a maximum concentration of 314ng/mL in 2.9 hours with an area under the curve of 4055ng/mL*hr. Subjects given a high fat meal and a 40mg oral doses reached a maximum concentration of 395ng/mL in 6.4 hours with an area under the curve of 6095ng/mL*mL.

Half Life

The half life ranges from 7-39 hours with a mean elimination half life of 20 hours. The half life of 4-oxo-13-cis-retinoic acid ranges from 17-50 hours with a mean elimination half life of 25 hours.

Clearance

The clearance of isotretinoin is 15.9L/h in pediatric patients with neuroblastoma. Clearance is also 21.3mL/min/kg in guinea pigs and 7.2mL/min/kg in obese rats.

Elimination Route

Stiefotrex and its metabolites are conjugated and excreted in the urine and feces in similar amounts. 53-74% of an oral dose is eliminated as unchanged isotretinoin in the feces.

Pregnancy & Breastfeeding use

Category X: Studies in animals or human beings have demonstrated foetal abnormalities or there is evidence of foetal risk based on human experience or both, and the risk of the use of the drug in pregnant women clearly outweighs any possible benefit. The drug is contraindicated in women who are or may become pregnant.

Contraindication

Hypervitaminosis A, hyperlipidaemia. Hepatic impairment. Pregnancy and lactation. Concomitant admin of tetracycylines.

Special Warning

Renal Impairment: Oral: Severe: Reduce initial dose (e.g. 10 mg daily), then gradually increase to 1 mg/kg as necessary.

Hepatic Impairment: Oral: Contraindicated.

Storage Condition

Store between 20-25° C. Protect from light.

Innovators Monograph

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