Isotretinoin

Indications and Usage

Severe Recalcitrant Nodular Acne

Zenatane is indicated 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. “Severe,” by definition, ²means “many” as opposed to “few or several” nodules. Because of significant adverse effects associated with its use, Zenatane should be reserved for patients with severe nodular acne who are unresponsive to conventional therapy, including systemic antibiotics.In addition, Zenatane is indicated only for those patients who are not pregnant, because Zenatane can cause life threatening birth defects (see Boxed CONTRAINDICATIONSAND WARNINGS ). 

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. ^1,3,4If 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 Zenatane. The optimal interval before retreatment has not been defined for patients who have not completed skeletal growth (see WARNINGS: Skeletal: Bone Mineral Density, Hyperostosis, Premature Epiphyseal Closure ).

Dosage and Administration

Zenatane should be administered with a meal (see PRECAUTIONS: Information for Patients ).

The recommended dosage range for Zenatane is 0.5 to 1 mg/kg/day given in two divided doses with food for 15 to 20 weeks. In studies comparing 0.1, 0.5, and 1 mg/kg/day, ⁸it was found that all dosages provided initial clearing of disease, but there was a greater need for retreatment with the lower dosages. During treatment, the dose may be adjusted according to response of the disease and/or the appearance of clinical side effects — some of which may be dose related. Adult patients whose disease is very severe with scarring or is primarily manifested on the trunk may require dose adjustments up to 2 mg/kg/day, as tolerated. Failure to take Zenatane with food will significantly decrease absorption. Before upward dose adjustments are made, the patients should be questioned about their compliance with food instructions.

The safety of once daily dosing with Zenatane has not been established. Once daily dosing is notrecommended.

If the total nodule count has been reduced by more than 70% prior to completing 15 to 20 weeks of treatment, the drug may be discontinued. After a period of 2 months or more off therapy, and if warranted by persistent or recurring severe nodular acne, a second course of therapy may be initiated. The optimal interval before retreatment has not been defined for patients who have not completed skeletal growth. Long-term use of Zenatane, even in low doses, has not been studied, and is not recommended. It is important that Zenatane be given at the recommended doses for no longer than the recommended duration. The effect of long-term use of Zenatane on bone loss is unknown (see WARNINGS: Skeletal: Bone Mineral Density , Hyperostosis , and Premature Epiphyseal closure ).

Contraceptive measures must be followed for any subsequent course of therapy (see PRECAUTIONS ).

Table 4 Zenatane Dosing by Body Weight (Based on Administration With Food)

*See DOSAGE AND ADMINISTRATION: the recommended dosage range is 0.5 to 1 mg/kg/day.

Contraindications

Pregnancy: Category X. See Boxed CONTRAINDICATIONS AND WARNINGS.

Allergic Reactions

Zenatane is contraindicated in patients who are hypersensitive to this medication or to any of its components (see PRECAUTIONS: Hypersensitivity).

Adverse Reactions

Clinical Trials and Postmarketing Surveillance

The adverse reactions listed below reflect the experience from investigational studies of Zenatane, and the postmarketing experience. The relationship of some of these events to Zenatane therapy is unknown. Many of the side effects and adverse reactions seen in patients receiving Zenatane are similar to those described in patients taking very high doses of vitamin A (dryness of the skin and mucous membranes, e.g., of the lips, nasal passage, and eyes).

Dose Relationship

Cheilitis and hypertriglyceridemia are usually dose related. Most adverse reactions reported in clinical trials were reversible when therapy was discontinued; however, some persisted after cessation of therapy (see WARNINGS and ADVERSE REACTIONS ).

Body as a Whole

allergic reactions, including vasculitis, systemic hypersensitivity (see PRECAUTIONS: Hypersensitivity ), edema, fatigue, lymphadenopathy, weight loss

Cardiovascular

palpitation, tachycardia, vascular thrombotic disease, stroke

Endocrine/Metabolic

hypertriglyceridemia (see WARNINGS: Lipids ), alterations in blood sugar levels (see PRECAUTIONS: Laboratory Tests ).

Gastrointestinal

inflammatory bowel disease (see WARNINGS: Inflammatory Bowel Disease ), hepatitis (see WARNINGS: Hepatotoxicity ), pancreatitis (see WARNINGS: Lipids ), bleeding and inflammation of the gums, colitis, esophagitis/esophageal ulceration, ileitis, nausea, other nonspecific gastrointestinal symptoms.

Hematologic

allergic reactions (see PRECAUTIONS: Hypersensitivity ), anemia, thrombocytopenia, neutropenia, rare reports of agranulocytosis (see PRECAUTIONS: Information for Patients ). See PRECAUTIONS: Laboratory Tests for other hematological parameters.

Musculoskeletal

skeletal hyperostosis, calcification of tendons and ligaments, premature epiphyseal closure, decreases in bone mineral density (see WARNINGS: Skeletal ), musculoskeletal symptoms (sometimes severe) including back pain, myalgia, and arthralgia (see PRECAUTIONS: Information for Patients ), transient pain in the chest (see PRECAUTIONS: Information for Patients ), arthritis, tendonitis, other types of bone abnormalities, elevations of CPK/rare reports of rhabdomyolysis (see PRECAUTIONS: Laboratory Tests ).

Neurological

pseudotumor cerebri (see WARNINGS: Pseudotumor Cerebri ), dizziness, drowsiness, headache, insomnia, lethargy, malaise, nervousness, paresthesias, seizures, stroke, syncope, weakness.

Psychiatric

suicidal ideation, suicide attempts, suicide, depression, psychosis, aggression, violent behaviors (see WARNINGS: Psychiatric Disorders ), emotional instability.

Of the patients reporting depression, some reported that the depression subsided with discontinuation of therapy and recurred with reinstitution of therapy.

Reproductive System

abnormal menses.

Respiratory

bronchospasms (with or without a history of asthma), respiratory infection, voice alteration

Skin and Appendages

acne fulminans, alopecia (which in some cases persists), bruising, cheilitis (dry lips), dry mouth, dry nose, dry skin, epistaxis, eruptive xanthomas, ⁷erythema multiforme, flushing, fragility of skin, hair abnormalities, hirsutism, hyperpigmentation and hypopigmentation, infections (including disseminated herpes simplex), nail dystrophy, paronychia, peeling of palms and soles, photoallergic/photosensitizing reactions, pruritus, pyogenic granuloma, rash (including facial erythema, seborrhea, and eczema), Stevens-Johnson syndrome, sunburn susceptibility increased, sweating, toxic epidermal necrolysis, urticaria, vasculitis (including Wegener’s granulomatosis; see PRECAUTIONS: Hypersensitivity ), abnormal wound healing (delayed healing or exuberant granulation tissue with crusting; see PRECAUTIONS: Information for Patients )

Special Senses

Hearing

hearing impairment (see WARNINGS: Hearing Impairment ), tinnitus.

Vision

corneal opacities (see WARNINGS: Corneal Opacities ), decreased night vision which may persist (see WARNINGS: Decreased Night Vision ), cataracts, color vision disorder, conjunctivitis, dry eyes, eyelid inflammation, keratitis, optic neuritis, photophobia, visual disturbances

Urinary System

glomerulonephritis (see PRECAUTIONS: Hypersensitivity ), nonspecific urogenital findings (see PRECAUTIONS: Laboratory Tests for other urological parameters)

Laboratory

Elevation of plasma triglycerides (see WARNINGS: Lipids ), decrease in serum high-density lipoprotein (HDL) levels, elevations of serum cholesterol during treatment

Increased alkaline phosphatase, SGOT (AST), SGPT (ALT), GGTP or LDH (see WARNINGS: Hepatotoxicity )

Elevation of fasting blood sugar, elevations of CPK (see PRECAUTIONS: Laboratory Tests ), hyperuricemia.

Decreases in red blood cell parameters, decreases in white blood cell counts (including severe neutropenia and rare reports of agranulocytosis; (see PRECAUTIONS: Information for Patients ), elevated sedimentation rates, elevated platelet counts, thrombocytopenia

White cells in the urine, proteinuria, microscopic or gross hematuria

Drug Interactions

Drug Interactions

• Vitamin A:Because of the relationship of Zenatane to vitamin A, patients should be advised against taking vitamin supplements containing vitamin A to avoid additive toxic effects.
• Tetracyclines:Concomitant treatment with Zenatane and tetracyclines should be avoided because Zenatane use has been associated with a number of cases of pseudotumor cerebri (benign intracranial hypertension), some of which involved concomitant use of tetracyclines.
• Micro-dosed Progesterone Preparations:Micro-dosed progesterone preparations (“minipills” that do not contain an estrogen) may be an inadequate method of contraception during Zenatane therapy. Although other hormonal contraceptives are highly effective, there have been reports of pregnancy from patients who can become pregnant who have used combined oral contraceptives, as well as transdermal patch/injectable/implantable/vaginal ring hormonal birth control products. These reports are more frequent for patients who can become pregnant who use only a single form of contraception. It is not known if hormonal contraceptives differ in their effectiveness when used with Zenatane. Therefore, it is critically important for patients who can become pregnant to select and commit to use two forms of effective contraception simultaneously, at least one of which must be a primary form (see PRECAUTIONS ).
• Norethindrone/ethinyl estradiol:In a study of 31 premenopausal female patients with severe recalcitrant nodular acne receiving Ortho-Novum ^®7/7/7 Tablets as an oral contraceptive agent, Zenatane at the recommended dose of 1 mg/kg/day, did not induce clinically relevant changes in the pharmacokinetics of ethinyl estradiol and norethindrone and in the serum levels of progesterone, follicle-stimulating hormone (FSH) and luteinizing hormone (LH). Prescribers are advised to consult the package insert of medication administered concomitantly with hormonal contraceptives, since some medications may decrease the effectiveness of these birth control products.
• St. John’s Wort: Zenataneuse is associated with depression in some patients (see WARNINGS: Psychiatric Disorders and ADVERSE REACTIONS : Psychiatric). Patients should be prospectively cautioned not to self-medicate with the herbal supplement St. John’s Wort because a possible interaction has been suggested with hormonal contraceptives based on reports of breakthrough bleeding on oral contraceptives shortly after starting St.John's Wort. Pregnancies have been reported by users of combined hormonal contraceptives who also used some form of St.John's Wort.
• Phenytoin:Zenatane has not been shown to alter the pharmacokinetics of phenytoin in a study in seven healthy volunteers. These results are consistent with the in vitro finding that neither isotretinoin nor its metabolites induce or inhibit the activity of the CYP 2C9 human hepatic P450 enzyme. Phenytoin is known to cause osteomalacia. No formal clinical studies have been conducted to assess if there is an interactive effect on bone loss between phenytoin and Zenatane. Therefore, caution should be exercised when using these drugs together.
• Systemic Corticosteroids:Systemic corticosteroids are known to cause osteoporosis. No formal clinical studies have been conducted to assess if there is an interactive effect on bone loss between systemic corticosteroids and Zenatane. Therefore, caution should be exercised when using these drugs together.

Overdosage

The oral LD ₅₀of isotretinoin is greater than 4000 mg/kg in rats and mice (>600 times the recommended clinical dose of 1 mg/kg/day after normalization of the rat dose for total body surface area and >300 times the recommended clinical dose of 1 mg/kg/day after normalization of the mouse dose for total body surface area) and is approximately 1960 mg/kg in rabbits (653 times the recommended clinical dose of 1 mg/kg/day after normalization for total body surface area). In humans, overdosage has been associated with vomiting, facial flushing, cheilosis, abdominal pain, headache, dizziness, and ataxia. These symptoms quickly resolve without apparent residual effects.

Zenatane causes life threatening birth defects at any dosage (see Boxed CONTRAINDICATIONS AND WARNINGS ). Patients who can become pregnant who present with isotretinoin overdose must be evaluated for pregnancy. Patients who are pregnant should receive counseling about the risks to the fetus, as described in the Boxed CONTRAINDICATIONS AND WARNINGS . Non-pregnant patients must be warned to avoid pregnancy for at least one month and receive contraceptive counseling as described in PRECAUTIONS . Educational materials for such patients can be obtained by calling the manufacturer. Because an overdose would be expected to result in higher levels of isotretinoin in semen than found during a normal treatment course, male patients should use a condom, or avoid reproductive sexual activity with a patient who is or might become pregnant, for one month after the overdose. All patients with isotretinoin overdose should not donate blood for at least one month.

Description

Isotretinoin USP, a retinoid, is available as Zenatane (isotretinoin capsules, USP) in 10 mg, 20 mg, 30 mg and 40 mg soft gelatin capsules for oral administration. Each capsule contains butylated hydroxyanisole, edetate disodium, hydrogenated vegetable oil (Type-I and Type-II), medium chain triglyceride, refined soybean oil and white wax. Gelatin capsules contain ferric oxide red, ferric oxide yellow (for 30 mg), gelatin, glycerin, methyl paraben, propyl paraben, lake blend blue(LB-332) containing D&C Yellow No.10, FD&C Blue No.1 (for 10 mg), lake blend red (LB-1574) containing D&C Red No.27, D&C Red No.30 (for 20 mg), lake blend green (LB-333) containing D&C Yellow No.10, FD&C Blue No.1 (for 40 mg), lake blend white (TLB-1774) containing FD&C Blue No.2, titanium dioxide, and opacode black S-1-17823 containing iron oxide black, N-butyl alcohol, propylene glycol, ammonium hydroxide and shellac.

Chemically, isotretinoin is 13-cis-retinoic acid and is related to both retinoic acid and retinol (vitamin A). It is a yellow to slightly orange crystalline powder with a molecular weight of 300.44. The structural formula is:

Meets USP DissolutionTest 5.

Clinical Pharmacology

Isotretinoin is a retinoid, which when administered in pharmacologic dosages of 0.5 to 1 mg/kg/day (see DOSAGE AND ADMINISTRATION ), inhibits sebaceous gland function and keratinization. The exact mechanism of action of isotretinoin is unknown.

Nodular Acne

Clinical improvement in nodular acne patients occurs in association with a reduction in sebum secretion. The decrease in sebum secretion is temporary and is related to the dose and duration of treatment with Zenatane, and reflects a reduction in sebaceous gland size and an inhibition of sebaceous gland differentiation. ¹

Pharmacokinetics

Absorption

Due to its high lipophilicity, oral absorption of isotretinoin is enhanced when given with a high-fat meal. In a crossover study, 74 healthy adult subjects received a single 80 mg oral dose (2 x 40 mg capsules) of Zenatane under fasted and fed conditions. Both peak plasma concentration (C _max) and the total exposure (AUC) of isotretinoin were more than doubled following a standardized high-fat meal when compared with Zenatane given under fasted conditions (see Table 2). The observed elimination half-life was unchanged. This lack of change in half-life suggests that food increases the bioavailability of isotretinoin without altering its disposition. The time to peak concentration (T _max) was also increased with food and may be related to a longer absorption phase. Therefore, Zenatane capsules should always be taken with food (see DOSAGE AND ADMINISTRATION ). Clinical studies have shown that there is no difference in the pharmacokinetics of isotretinoin between patients with nodular acne and healthy subjects with normal skin.

Table 2 Pharmacokinetic Parameters of Isotretinoin Mean (%CV), N=74

*Eating a standardized high-fat meal.

Distribution

Isotretinoin is more than 99.9% bound to plasma proteins, primarily albumin.

Metabolism

Following oral administration of isotretinoin, at least three metabolites have been identified in human plasma: 4-oxo-isotretinoin, retinoic acid (tretinoin), and 4-oxo-retinoic acid (4-oxotretinoin). Retinoic acid and 13-cis-retinoic acid are geometric isomers and show reversible interconversion. The administration of one isomer will give rise to the other. Isotretinoin is also irreversibly oxidized to 4-oxo-isotretinoin, which forms its geometric isomer 4-oxo-tretinoin.

After a single 80 mg oral dose of Zenatane to 74 healthy adult subjects, concurrent administration of food increased the extent of formation of all metabolites in plasma when compared to the extent of formation under fasted conditions.

All of these metabolites possess retinoid activity that is in some in vitro models more than that of the parent isotretinoin. However, the clinical significance of these models is unknown. After multiple oral dose administration of isotretinoin to adult cystic acne patients (≥18 years), the exposure of patients to 4-oxo-isotretinoin at steady-state under fasted and fed conditions was approximately 3.4 times higher than that of isotretinoin.

In vitro studies indicate that the primary P450 isoforms involved in isotretinoin metabolism are 2C8, 2C9, 3A4, and 2B6.  Isotretinoin and its metabolites are further metabolized into conjugates, which are then excreted in urine and feces.

Elimination

Following oral administration of an 80 mg dose of ¹⁴C-isotretinoin as a liquid suspension, ¹⁴C-activity in blood declined with a half-life of 90 hours. The metabolites of isotretinoin and any conjugates are ultimately excreted in the feces and urine in relatively equal amounts (total of 65% to 83%). After a single 80 mg oral dose of Zenatane to 74 healthy adult subjects under fed conditions, the mean ± SD elimination half-lives (t _1/2) of isotretinoin and 4- oxo-isotretinoin were 21 ± 8.2 hours and 24 ± 5.3 hours, respectively. After both single and multiple doses, the observed accumulation ratios of isotretinoin ranged from 0.9 to 5.43 in patients with cystic acne.

Special Patient Populations

Pediatric Patients

The pharmacokinetics of isotretinoin were evaluated after single and multiple doses in 38 pediatric patients (12 to 15 years) and 19 adult patients (≥18 years) who received Zenatane for the treatment of severe recalcitrant nodular acne. In both age groups, 4-oxo-isotretinoin was the major metabolite; tretinoin and 4-oxo-tretinoin were also observed. The dose-normalized pharmacokinetic parameters for isotretinoin following single and multiple doses are summarized in Table 3for pediatric patients. There were no statistically significant differences in the pharmacokinetics of isotretinoin between pediatric and adult patients.

Table 3. Pharmacokinetic Parameters of Isotretinoin Following Single and Multiple Dose Administration in Pediatric Patients, 12 to 15 Years of Age Mean (± SD), N=38*

*The single and multiple dose data in this table were obtained following a non-standardized meal that is not comparable to the high-fat meal that was used in the study in Table 2.

† Median (range)

In pediatric patients (12 to 15 years), the mean ± SD elimination half-lives (t _1/2) of isotretinoin and 4-oxo-isotretinoin were 15.7 ± 5.1 hours and 23.1 ± 5.7 hours, respectively. The accumulation ratios of isotretinoin ranged from 0.46 to 3.65 for pediatric patients.

How Supplied / Storage and Handling

Zenatane (isotretinoin capsules USP) 10 mg are opaque blue elliptical soft gelatin capsules imprinted with black ink, “R135” on one side and are supplied in boxes of 30 containing 3 prescription packs of 10 capsules as unit dose blisters.

Unit dose blister of 10 capsules NDC: 68001-652-16

Boxes of 30 (3 Prescription Packs of 10 capsules) NDC: 68001-652-17

Zenatane (isotretinoin capsules USP) 20 mg are opaque pink elliptical soft gelatin capsules imprinted with black ink, “R136” on one side and are supplied in boxes of 30 containing 3 prescription packs of 10 capsules as unit dose blisters.

Unit dose blister of 10 capsules NDC: 68001-653-16

Boxes of 30 (3 Prescription Packs of 10 capsules) NDC: 68001-653-17

Zenatane (isotretinoin capsules USP) 30 mg are reddish brown colored opaque, elliptical shaped soft gelatin capsule imprinted with “RI” black colored ink along the length of body on one side and are supplied in boxes of 30 containing 3 prescription packs of 10 capsules as unit dose blisters.

Unit dose blister of 10 capsules NDC: 68001-654-16

Boxes of 30 (3 Prescription Packs of 10 capsules) NDC: 68001-654-17

Zenatane (isotretinoin capsules USP) 40 mg are opaque green elliptical soft gelatin capsules imprinted with black ink, “R137” on one side and are supplied in boxes of 30 containing 3 prescription packs of 10 capsules as unit dose blisters.

Unit dose blister of 10 capsules NDC: 68001-655-16

Boxes of 30 (3 prescription packs of 10 capsules) NDC: 68001-655-17