Tretin-C

Tretin-C is indicated for the topical treatment of acne vulgaris when comedones, papules and pustules are present in patients 12 years or older

Consideration should be given to official guidance on the appropriate use of antibacterial agents and acne treatment.

Posology

Adults and adolescents (> 12 years)

Once daily at bedtime the entire face should be washed with mild soap and dried. A pea-sized amount of medication should be squeezed onto one fingertip, dot onto the chin, cheeks, nose, and forehead; then gently rub over the entire face.

Treatment with Tretin-C should not exceed 12 weeks of continuous use without careful evaluation. It should be noted that therapeutic improvement may not be observed for several weeks after starting treatment.

In case of a missed dose of Tretin-C, the patient should wait for the next dose at the usual time. Patients should not double the dose to make up for the forgotten dose.

Use in Children below 12 years of age

Tretin-C is not recommended for use in children below 12 years of age, since safety and efficacy of Tretin-C in children have not been established.

Use in the Elderly (>65 years of age)

Safety and efficacy of Tretin-C in patients above the age of 65 years have not been established.

Renal and hepatic impairment

In view of the low systemic exposure to clindamycin and tretinoin following topical administration of Tretin-C, moderate renal or hepatic impairment is not expected to result in systemic exposure of clinical concern. However, clindamycin and tretinoin serum concentrations have not been studied in patients with renal or hepatic disease following topical administration. Individual decisions are advisable in severe cases.

Method of administration

Tretin-C is indicated for external (dermatological) use only. The application of Tretin-C should avoid eyes, eyelids, lips and nostrils. After the application the patient should wash hands.

Tretin-C is contraindicated:

- In patients who have a history of hypersensitivity to the active substances clindamycin and/or tretinoin or to any of the excipients or lincomycin (see also Section 6.1)

- In patients with regional enteritis, ulcerative colitis, or history of antibiotic-associated colitis

- In patients who have a personal or familial history of skin cancer

- In patients who have a history of acute eczemas, rosacea and perioral dermatitis

- In patients with pustular and deep cystic nodular acne varieties (acne conglobata and acne fulminans).

Tretin-C is not for oral, ophthalmic, intranasal or intravaginal use.

Tretin-C is not recommended in treatment of mild acne vulgaris.

Tretin-C should not be used in pregnancy, especially during the first trimester, and in women of childbearing potential not using contraception

Contact with the mouth, eyes and mucous membranes and with abraded or eczematous skin should be avoided. Application to sensitive areas of skin should be made with caution. In the event of accidental contact with the eyes, bathe with large amounts of water.

Antibiotic-associated colitis (also known as Clostridium difficile-associated colitis or CDAD) has been reported with the use of some other topical clindamycin products. This is unlikely to occur with Tretin-C, as plasma levels have been determined and the percutaneous absorption of clindamycin is clinically negligible.

If prolonged or significant diarrhoea occurs or the patient suffers from abdominal cramps, treatment with Tretin-C should be discontinued immediately, as the symptoms may indicate antibiotic-associated colitis. Suitable diagnostic methods, such as the determination of Clostridium difficile and toxin and, if necessary, colonoscopy should be employed and treatment options for colitis considered.

Use of more than the recommended amount or too frequent application may cause redness, stinging and discomfort. If severe irritation occurs, especially in the early stage of therapy, patient should be advised to discontinue temporarily or reduce the frequency of application.

Tretin-C should be prescribed with caution in atopic subjects.

Tretin-C should not be applied at the same time as other topical preparations (including cosmetics) because of possible incompatibility and interaction with tretinoin. Particular caution should be exercised in the use of keratolytic agents such as sulphur, salicylic acid, benzoyl peroxide or resorcinol and chemical abrasives. If the patient has been treated with such preparations, the effect of the peeling agents must subside before any commencement of Tretin-C therapy.

Some medicated cleansers and scrubbing solutions have a strong drying effect. They should not be used in patients receiving tretinoin topical therapy. Abrasive soaps, soaps and cosmetics as well as spices or lime should be used with caution.

Because of increased susceptibility to UV radiation, photosensitivity may occur during treatment with Tretin-C Gel. Exposure to sunlight should therefore be minimised and appropriate sunscreen products with a SPF (Sun Protection Factor) of at least 30, together with suitable protective apparel (e.g. a hat), should be used. Use of sun lamps or sun beds should be avoided during treatment and patients with sunburn should not use this product until recovered

Patients who may be required to have considerable sun exposure due to occupation and those with inherent sensitivity to the sun should exercise particular caution. If sunburn occurs, discontinue therapy with Tretin-C until the severe erythema and peeling subside.

Occasional gram-negative folliculitis has been reported during treatment with clindamycin 1% topical products. If this should occur, therapy with Tretin-C should be discontinued and alternative therapy should be initiated.

Long-term use of clindamycin may cause resistance and/or overgrowth of non susceptible dermal bacteria or fungi although this is a rare occurrence.

Cross resistance may occur with other antibiotics such as lincomycin or erythromycin

Simultaneous use of oral and topical antibiotics should be avoided, particularly if chemically different.

The excipients methyl parahydroxybenzoate (E218) and propyl parahydroxybenzoate (E216) may cause allergic reactions (possibly delayed). The excipient butylhydroxytoluene (E321) may cause local skin reactions (e.g. contact dermatitis), or irritation to the eyes and mucous membranes.

No studies on the effects on the ability to drive and use machines have been performed. It is unlikely that treatment with Tretin-C will have any effect on the ability to drive and use machines.

Within the system organ classes, adverse reactions are listed under headings of frequency (number of patients expected to experience the reaction), using the following categories:

Very common (>1/10)

Common (>1/100 to <1/10)

Uncommon (>1/1,000 to <1/100)

Rare (>1/10,000 to <1/1,000)

Very rare (<1/10,000)

Not known (cannot be estimated from the available data)

Reported frequencies in clinical trials are as following:

Immune system disorders:

Rare: Hypersensitivity

Endocrine disorders:

Rare: Hypothyroidism

Nervous system disorders:

Rare: Headache

Eye disorders:

Rare: Eye irritation

Gastrointestinal disorders:

Rare: Gastroenteritis, nausea

Skin and subcutaneous tissue disorders:

Uncommon: Acne, dry skin, erythema, seborrhoea, photosensitivity reaction, pruritis, rash, exfoliative rash, skin exfoliation, sunburn

Rare: Dermatitis, herpes simplex, macular rash, skin bleeding, skin burning sensation, skin depigmentation, skin irritation.

General disorders and administration site conditions:

Uncommon: Application site reaction, application site burning, application site dermatitis, application site dryness, application site erythema,

Rare: Application site irritation, application site swelling, application site erosion, application site discolouration, application site pruritus, application site desquamation, feeling hot, pain

Paediatric population

The proportion of paediatric patients (12-17 years) reporting a specific drug-related adverse reaction was consistent with that which was reported in the overall population. The incidence of dry skin in adolescent population (12-17 years) was slightly higher in clinical trials than in the overall population.

Reporting of suspected adverse reactions

Reporting suspected adverse reactions after authorisation of the medicinal product is important. It allows continued monitoring of the benefit/risk balance of the medicinal product. Healthcare professionals are asked to report any suspected adverse reactions via the Yellow Card Scheme at: www.mhra.gov.uk/yellowcard.

Tretin-C Gel is for topical use only. If Tretin-C Gel is applied excessively, marked redness, peeling or discomfort can occur. If excess application occurs accidentally or through over-enthusiastic use, the face should be gently washed with a mild soap and lukewarm water. Tretin-C should be discontinued for several days before resuming therapy.

In the case of overdosage, topically applied clindamycin phosphate from Tretin-C can be absorbed in sufficient amounts to cause systemic effects. Gastrointestinal side effects including abdominal pain, nausea, vomiting and diarrhoea may occur

In the event of accidental ingestion, treatment should be symptomatic. The same adverse reactions effects as those expected with clindamycin (i.e. abdominal pain, nausea, vomiting and diarrhoea) and tretinoin (including teratogenesis in women of childbearing years) are expected. In such cases, Tretin-C Gel should be discontinued and pregnancy testing should be carried out in women of childbearing potential.

Pharmacotherapeutic group: Anti-Acne Preparations for Topical Use; clindamycin, combinations

ATC code: D10AF51

Tretin-C combines two active substances, which act through different mechanisms of action (see below).

Clindamycin:

Clindamycin is a semisynthetic derivative of the parent compound lincomycin that is produced by Streptomyces lincolnensis and is predominantly bacteriostatic. Clindamycin binds to the 50S ribosomal subunits of susceptible bacteria and prevents elongation of peptide chains by interfering with peptidyl transfer, thereby suppressing bacterial protein synthesis. Although clindamycin phosphate is inactive in-vitro, rapid in-vivo hydrolysis converts this compound to the antibacterial active clindamycin.

Clindamycin has been shown to have in vitro activity against Propionibacterium acnes, one pathophysiological factor that influence the development of acne vulgaris. Clindamycin also exerts an anti-inflammatory effect on the acne vulgaris lesions.

The break-point for susceptibility testing of clindamycin is 4 mg/ml for P. acnes as a representative of Gram-positive anaerobes (breakpoints for susceptibility recommended by the European Committee on Antimicrobial Susceptibility Testing - EUCAST).

Tretinoin:

Topical tretinoin has both comedolytic and anti-inflammatory effects. Tretinoin decreases cohesiveness of follicular epithelial cells resulting in decreased microcomedone formation. Additionally, tretinoin stimulates mitotic activity and increased turnover of follicular epithelial cells, causing extrusion of the comedones. The comedolytic activity is related to a normalisation of the desquamation of the follicular epithelium. Tretinoin exerts anti-inflammatory effect via suppression of toll-like receptors (TLRs).

A combination therapy of clindamycin and tretinoin, as in Tretin-C Gel, not only combines the individual actions of both active agents but also complements their certain actions. There is also evidence in the literature to show that when applied together, tretinoin increases the penetration of clindamycin. Thus, this combination therapy targets multiple pathogenic factors: abnormal follicular keratinization, P.acnes proliferation, inflammation and increased sebum production.

Clinical efficacy of Tretin-C

Three randomised double-blind clinical studies, including a total of 4550 patients with acne vulgaris with both inflammatory and non-inflammatory lesions were performed. Of these 1853 patients were treated with Tretin-C Gel, 846 with tretinoin, 1428 with clindamycin phosphate and 423 with Tretin-C Gel vehicle.

Patients with 20-50 facial acne inflammatory lesions (papules and pustules), 20-100 facial acne non-inflammatory lesions (open and closed comedones), two or fewer nodules (defined as an inflammatory lesion greater than or equal to 5 mm in diameter) and without cysts were included. Lesions were counted at baseline and at weeks 2, 4, 8 and 12.

Primary measurements of efficacy for studies 7001.G2HP-06-02 and 7001.G2HP-07-02 were (1) mean percent change from baseline at Week 12 in inflammatory lesion counts, (2) mean percent change from baseline at Week 12 in non inflammatory lesion counts, (3) mean percent change from baseline at Week 12 in total lesion counts, and (4) the percent of subjects who were clear or almost clear, at Week 12 as judged by an Evaluator's Global Severity Score (EGSS). Superiority vs. monotherapies was concluded if two of three lesion count variables and dichotomized EGSS were significant.

Treatment was applied once daily for 12 weeks and patients were evaluated and lesions counted at week 12.

Studies 7001.G2HP-06-02 and 7001.G2HP-07-02 compared Tretin-C to both mono treatments (clindamycin phosphate 1.2% gel and tretinoin 0.025% gel) and vehicle using a double-blind treatment regimen. The third clinical study (MP1501-02) was conducted to compare Tretin-C to clindamycin alone.

The distribution of percent change in lesion counts was skewed, therefore the median percent change is shown in the following tables.

Global Severity Score at Week 12 -presented as dichotomised values

¹ missing values imputed as failures

* Study 7001-G2HP-06-02

** Study 7001-G2HP-07-02

*** Study MP-1501-02

Paediatric Population

The percentage change in the number of lesions at Week 12 for adolescents, between 12 and 17 years, in the individual trials and the metanalysis of these trials are provided below.

Although the studies were not powered for the subgroups and the results are not as consistent as for the changes in lesion counts, they also provide evidence for superiority of the combination product.

In an open-label, multiple-dose study treating 12 subjects with moderate to severe acne, the percutaneous absorption of tretinoin following 14 consecutive daily applications of approximately 4 g of Tretin-C was minimal. Tretinoin plasma concentrations were below the lower limit of quantitation (LLOQ; 1 ng/mL) in 50% to 92% of subjects at any given time point following administration and were near the LLOQ in the remaining subjects, with values ranging from 1.0 to 1.6 ng/mL. The plasma concentrations of the key tretinoin metabolites, 13-cis-retinoic acid and 4-oxo-13-cis-retinoic acid, ranged from 1.0 to 1.4 ng/mL and from 1.6 to 6.5 ng/mL, respectively. Plasma concentrations for clindamycin generally did not exceed 3.5 ng/mL, with the exception of one subject whose plasma concentration reached 13.1 ng/mL.

Tretinoin

Tretinoin occurs in the body as a metabolite of retinol, and it exhibits a certain degree of Vitamin A growth-promoting activity. Representative well-controlled clinical studies conclude that topically applied tretinoin does not increase plasma alltrans retinoic acid (tretinoin). Following a single topical application of radiolabelled tretinoin, the blood concentration of retinoic acid was found to be unchanged from 2-48 hours. Neither single-dose nor long-term treatment with topical tretinoin formulations does alter systemic retinoid levels, which remain within the range of body's natural endogenous levels.

Clindamycin

Clindamycin is converted within the skin by phosphatases, leading to the more potent from of clindamycin. Thus, conversion to clindamycin is a major determinant of antimicrobial activity in the skin layers following topical application of clindamycin phosphate.

Following preclinical studies of Tretin-C, clindamycin, and tretinoin support the safety of Tretin-C.

Tretin-C

A 13 week repeat-dose dermal toxicity study in minipigs revealed no toxic effects, apart from minor local irritation (erythema). Tretin-C Gel was shown not to be a primary skin irritant or ocular irritant in two local tolerance studies in rabbits, and it was shown not to be a contact sensitizer in guinea pigs.

In a dermal developmental toxicity study in rabbits no reproductive toxicity was seen.

Clindamycin

Systemically administered clindamycin does not affect fertility, mating ability, embryonic development, or post-natal development. In-vitro and in-vivo studies did not reveal any mutagenic potential of clindamycin. Clindamycin was not carcinogenic in mice in a 2-year dermal study with 1.2% clindamycin phosphate and a 2-year oral study in rats.

Tretinoin

In-vitro and in-vivo studies did not reveal any mutagenic potential of tretinoin. Tretinoin was not carcinogenic in mice in a 2-year dermal study with 0.1% tretinoin (a higher strength than Tretin-C). The systemic carcinogenic potential has not been studied. Oral tretinoin has been shown to be teratogenic in rats, mice, hamsters, rabbits, monkeys and humans. It severely affects fertility and peri-postnatal development. In animals, dermally applied tretinoin was not teratogenic at daily doses that were several times higher than the human recommended daily dose adjusted to body surface.

No special requirements.