Clindamycin Phosphate and Tretinoin

Systemic absorption of clindamycin has been demonstrated following topical use of this product. Diarrhea, bloody diarrhea, and colitis (including pseudomembranous colitis) have been reported with the use of topical clindamycin. When significant diarrhea occurs, clindamycin phosphate and tretinoin gel should be discontinued.

Severe colitis has occurred following oral or parenteral administration of clindamycin with an onset of up to several weeks following cessation of therapy. Antiperistaltic agents such as opiates and diphenoxylate with atropine may prolong and/or worsen severe colitis. Severe colitis may result in death.

Studies indicate a toxin(s) produced by clostridia is one primary cause of antibiotic-associated colitis. The colitis is usually characterized by severe persistent diarrhea and severe abdominal cramps and may be associated with the passage of blood and mucus. Stool cultures for Clostridium difficile and stool assay for C. difficile toxin may be helpful diagnostically.

Exposure to sunlight, including sunlamps, should be avoided during the use of clindamycin phosphate and tretinoin gel, and patients with sunburn should be advised not to use the product until fully recovered because of heightened susceptibility to sunlight as a result of the use of tretinoin. 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. Daily use of sunscreen products and protective apparel (e.g., a hat) are recommended. Weather extremes, such as wind or cold, also may be irritating to patients under treatment with clindamycin phosphate and tretinoin gel.

Because clinical trials are conducted under prescribed conditions, adverse reaction rates observed in the clinical trial may not reflect the rates observed in practice. The adverse reaction information from clinical trials does, however, provide a basis for identifying the adverse reactions that appear to be related to drug use for approximating rates.

The safety data presented in Table 1 (below) reflects exposure to clindamycin phosphate and tretinoin gel in 1,853 patients with acne vulgaris. Patients were 12 years and older and were treated once daily for 12 weeks. Adverse reactions that were reported in ≥ 1% of patients treated with clindamycin phosphate and tretinoin gel were compared to adverse reactions in patients treated with clindamycin phosphate 1.2% in vehicle gel, tretinoin 0.025% in vehicle gel, and the vehicle gel alone:

Cutaneous safety and tolerance evaluations were conducted at each study visit in all of the clinical trials by assessment of erythema, scaling, itching, burning, and stinging:

At each study visit, application site reactions on a scale of 0 (none), 1 (mild), 2 (moderate), and 3 (severe), and the mean scores were calculated for each of the local skin reactions. In Studies 1 and 2, 1277 subjects enrolled with moderate to severe acne, 854 subjects treated with clindamycin phosphate and tretinoin gel and 423 treated with vehicle. Analysis over the twelve week period demonstrated that cutaneous irritation scores for erythema, scaling, itching, burning, and stinging peaked at two weeks of therapy, and were slightly higher for the clindamycin phosphate and tretinoin-treated group, decreasing thereafter.

One open-label 12-month safety study for clindamycin phosphate and tretinoin gel showed a similar adverse reaction profile as seen in the 12-week studies. Eighteen out of 442 subjects (4%) reported gastrointestinal symptoms.

Concomitant topical medication, medicated or abrasive soaps and cleansers, soaps and cosmetics that have a strong drying effect, and products with high concentrations of alcohol, astringents, spices or lime should be used with caution. When used with clindamycin phosphate and tretinoin gel, there may be increased skin irritation.

Clindamycin phosphate and tretinoin gel should not be used in combination with erythromycin-containing products due to its clindamycin component. In vitro studies have shown antagonism between these two antimicrobials. The clinical significance of this in vitro antagonism is not known.

Clindamycin has been shown to have neuromuscular blocking properties that may enhance the action of other neuromuscular blocking agents. Therefore, clindamycin phosphate and tretinoin gel should be used with caution in patients receiving such agents.

Pregnancy Category C. There are no well-controlled trials in pregnant women treated with clindamycin phosphate and tretinoin gel. Clindamycin phosphate and tretinoin gel should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus. Clindamycin phosphate and tretinoin gel was tested for maternal and developmental toxicity in New Zealand White Rabbits with topical doses of 60, 180 and 600 mg/kg/day. Clindamycin phosphate and tretinoin gel at 600 mg/kg/day (approximately 12 times the recommended clinical dose assuming 100% absorption and based on body surface area comparison) was considered to be the no-observed-adverse-effect level (NOAEL) for maternal and developmental toxicity following dermal administration of clindamycin phosphate and tretinoin gel for two weeks prior to artificial insemination and continuing until gestation day 18, inclusive. For purposes of comparisons of the animal exposure to human exposure, the recommended clinical dose is defined as 1 g of clindamycin phosphate and tretinoin gel applied daily to a 60 kg person.

Clindamycin

Teratology (Segment II) studies using clindamycin were performed orally in rats (up to 600 mg/kg/day) and mice (up to 100 mg/kg/day) (583 and 49 times amount of clindamycin in the recommended clinical dose based on a body surface area comparison, respectively) or with subcutaneous doses of clindamycin up to 180 mg/kg/day (175 and 88 times the amount of clindamycin in the recommended clinical dose based on a body surface area comparison, respectively) revealed no evidence of teratogenicity.

Tretinoin

In oral Segment III studies in rats with tretinoin, decreased survival of neonates and growth retardation were observed at doses in excess of 2 mg/kg/day (~ 78 times the recommended clinical dose assuming 100% absorption and based on body surface area comparison).

With widespread use of any drug, a small number of birth defect reports associated temporally with the administration of the drug would be expected by chance alone. Thirty cases of temporally associated congenital malformations have been reported during two decades of clinical use of another formulation of topical tretinoin. Although no definite pattern of teratogenicity and no causal association have been established from these cases, 5 of the reports describe the rare birth defect category, holoprosencephaly (defects associated with incomplete midline development of the forebrain). The significance of these spontaneous reports in terms of risk to the fetus is not known.

Dermal tretinoin has been shown to be fetotoxic in rabbits when administered in doses 40 times the recommended human clinical dose based on a body surface area comparison. Oral tretinoin has been shown to be fetotoxic in rats when administered in doses 78 times the recommended clinical dose based on a body surface area comparison.

It is not known whether clindamycin is excreted in human milk following use of clindamycin phosphate and tretinoin gel. However, orally and parenterally administered clindamycin has been reported to appear in breast milk. Because of the potential for serious adverse reactions in nursing infants, a decision should be made whether to discontinue nursing or to discontinue the drug, taking into account the importance of the drug to the mother. It is not known whether tretinoin is excreted in human milk. Because many drugs are excreted in human milk, caution should be exercised when clindamycin phosphate and tretinoin gel is administered to a nursing woman.

Safety and effectiveness of clindamycin phosphate and tretinoin gel in pediatric patients under the age of 12 have not been established.

Clinical trials of clindamycin phosphate and tretinoin gel included patients 12 to 17 years of age. [See Clinical Studies (14)]

Clinical studies of clindamycin phosphate and tretinoin gel did not include sufficient numbers of subjects aged 65 and over to determine whether they respond differently from younger subjects.

Clindamycin

[see Microbiology (12.4)].

Tretinoin

Although the exact mode of action of tretinoin is unknown, current evidence suggests that topical tretinoin decreases cohesiveness of follicular epithelial cells with decreased microcomedo formation. Additionally, tretinoin stimulates mitotic activity and increased turnover of follicular epithelial cells causing extrusion of the comedones.

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 clindamycin phosphate and tretinoin gel was minimal. Quantifiable tretinoin plasma concentrations ranged from 1.0 to 1.6 ng/mL, with unquantifiable plasma concentrations in 50% to 92% of subjects at any given timepoint following administration. 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.

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. Clindamycin has been shown to have in vitro activity against Propionibacterium acnes, an organism which has been associated with acne vulgaris; however, the clinical significance of this activity against P. acnes was not examined in clinical trials with clindamycin phosphate and tretinoin gel. P acnes resistance to clindamycin has been documented. Resistance to clindamycin is often associated with resistance to erythromycin.

Carcinogenicity, mutagenicity and impairment of fertility testing of clindamycin phosphate and tretinoin gel have not been performed in any species.

Clindamycin

The carcinogenicity of a 1% clindamycin phosphate gel similar to clindamycin phosphate and tretinoin gel was evaluated by daily application to mice for two years. The daily doses used in this study were approximately 13 and 72 times higher than the human dose of clindamycin phosphate from clindamycin phosphate and tretinoin gel, assuming complete absorption and based on a body surface area comparison. No significant increase in tumors was noted in the treated animals. For purposes of comparisons of the animal exposure to human exposure, the recommended human topical clinical dose is defined as 1 g of clindamycin phosphate and tretinoin gel applied daily to a 60 kg person.

Fertility (Segment 1) studies in rats treated orally with up to 300 mg/kg/day of clindamycin (approximately 290 times the amount of clindamycin delivered from the recommended clinical dose for clindamycin phosphate and tretinoin gel, based on a body surface area comparison) revealed no effects on fertility or mating ability.

Tretinoin

In two independent studies with long-term topical application of tretinoin in mice, carcinogenicity was not observed. In both studies, tretinoin was administered topically (0.025% or 0.1%) three times per week for up to two years. No carcinogenicity was observed with maximum effects of dermal amyloidosis in the basal layer of the skin.

Tretinoin has been shown to enhance photoco-carcinogenicity in properly performed specific studies, employing concurrent or intercurrent exposure to the drug and UV radiation. The contribution of clindamycin to that effect is unknown. Although the significance of these studies to humans is not clear, patients should minimize exposure to sun.

The genotoxic potential of tretinoin was evaluated in an in vitro Ames Salmonella reversion test and an in vitro chromosomal aberration assay in Chinese hamster ovary cells. Both tests were negative.

In oral Segment 1 studies in rats treated with tretinoin, the no-observed-effect-level was 2 mg/kg/day (~78 times the recommended clinical dose assuming 100% absorption and based on body surface area comparison).

• At bedtime, the face should be gently washed with a mild soap and warm water. After patting the skin dry, apply clindamycin phosphate and tretinoin gel as a thin layer over the entire face (excluding the eyes and lips).
• Patients should be advised not to use more than the recommended pea sized amount and not to apply more often than once daily (at bedtime) as this will not make for faster results and may increase irritation.
• A sunscreen should be applied every morning and reapplied over the course of the day as needed. Patients should be advised to avoid exposure to sunlight, sunlamp, ultraviolet light, and other medicines that may increase sensitivity to sunlight.

Clindamycin phosphate and tretinoin gel may cause irritation such as erythema, scaling, itching, burning, or stinging.

In the event a patient treated with clindamycin phosphate and tretinoin gel experiences severe diarrhea or gastrointestinal discomfort, clindamycin phosphate and tretinoin gel should be discontinued and a physician should be contacted.

Manufactured For:
Teva Pharmaceuticals
Parsippany, NJ 07054

Rev. B 2/2023