Benzoyl peroxide: percutaneous penetration and metabolic disposition

Treatment of Acne Vulgaris During Pregnancy and Lactation: A Narrative Review

Acne vulgaris frequently affects women during pregnancy and lactation. Hormonal and physiologic changes in pregnancy contribute to the pathogenesis of acne during the various phases of pregnancy. Several effective acne treatments commonly prescribed in the general population are contraindicated during pregnancy or lactation. There is a lack of guidelines and updated resources on acne management in these populations. In this narrative review, we summarize existing evidence on the safety and efficacy of acne treatments during pregnancy and breastfeeding. Acne management in pregnancy and lactation should follow a stepwise approach based on severity to minimize risk. Topical therapies, such as benzoyl peroxide, azelaic acid, or keratolytics, can be used to treat mild-to-moderate disease. Moderate-to-severe acne may require systemic treatments, including penicillin, amoxicillin, cephalexin, and erythromycin, with special consideration for trimester-specific teratogenicity of medications and relevant medical history of the mother and infant. For refractory cases, oral or intralesional corticosteroids as well as laser and light therapies may be considered. This review provides an updated reference to aid patient-physician decision-making on acne management in these special populations.

Adverse events related to topical drug treatments for acne vulgaris

Introduction: Acne vulgaris is a widespread skin disease. Topical therapy is a standard treatment for mild to moderate acne. Given the complex pathophysiology of acne, various agents with complementary action are nowadays frequently combined to increase the efficacy of therapy.Area covered: This review focus on safety profile of topical agents used for the treatment of acne vulgaris, including topical retinoids, benzyl peroxide, azelaic acid, topical antibiotic, and combined agents. Data from clinical trials but also metanalyses, systematic reviews, and other secondary analyses are presented.Expert opinion: In general, topical agents used for acne vulgaris have a favorable safety profile. The most commonly reported AEs were associated with local skin irritation, usually mild to moderate in intensity, intermittent, and rarely led to the cessation of therapy. Irritative potential seems to be highest for BPO and topical retinoids. Due to the possibility of development of Cutibacterium acnes resistance, topical antibiotics should not be used in monotherapy but as a part of combination therapy. In female adolescent and adults of childbearing potential, topical retinoids should be used with caution, because they are contraindicated in pregnant females (FDA Pregnancy category) C (adapalene, tretinoin) and X (tazarotene).

An update on formulation strategies of benzoyl peroxide in efficient acne therapy with special focus on minimizing undesired effects

Benzoyl peroxide (BPO) in the form of over the counter monotherapeutics or prescription-only combinations is a key component of topical acne therapy, but its unfavourable side effect profile reduces the therapeutic value of this compound. Various galenic approaches have been pursued to resolve this ambivalence, but only a few have managed to enter the market. This article aims to give a comprehensive overview of the published experimental vehicle systems and to identify the fundamental rationales. With regard to the formulation, an increase in the tolerability of BPO can essentially be achieved by combining BPO with re-fattening and moisturizing substances, by incorporating it and controlling its release, as well as by targeted deposition of the active ingredient at the site of action, i.e. drug targeting. Recently, novel particulate formulations have been proposed that combine several of these design principles and are expected to bring new developments in this dynamic field of research.

Systemic exposure to benzoic acid and hippuric acid following topical application of clindamycin 1%/benzoyl peroxide 3% fixed-dose combination gel in Japanese patients with acne vulgaris

Clindamycin 1%/benzoyl peroxide 3% fixed-dose combination gel (CLDM/BPO3%) is a topical product for the treatment of acne vulgaris. In this study, plasma and urine concentrations of benzoic acid (BA) and hippuric acid (HA) were analyzed to estimate the pharmacokinetics (PK) of BPO after application of CLDM/BPO3% twice-daily for 7 days in Japanese patients with acne vulgaris. Seven-day repeated application of CLDM/BPO3% appears to be safe in this patient population. Concentrations of plasma and urine BA were below the limit of quantification before and after repeated application in most of the 12 adult male patients. Mean difference in Cmax and AUC0-last for plasma HA indicated increased exposures after repeated application, but with wide 90% confidence intervals. Mean Ae0-12 for urine HA was similar before and after repeated application. Repeated application of CLDM/BPO3% is thus unlikely to result in accumulation of BA and HA. The study suggests negligible systemic exposure to BPO metabolites from CLDM/BPO3% after 7-day repeated application in male patients with acne vulgaris.

The management of acne vulgaris in pregnancy

Acne vulgaris is a common condition in adolescence and also for many women of childbearing age. The management of acne in pregnancy is complicated by the lack of clinical studies and pharmacokinetic data in this patient population and safety concerns regarding retinoid use in pregnancy. Of primary concern to both patients and clinicians is the safety profile of medications used during pregnancy. This review seeks to clarify what management options are available to treat acne during pregnancy and what data are available to guide decision making. Topical treatments are considered the safest option during pregnancy. They have the best safety profile and minimize the levels of systemic absorption, and therefore the least risk of fetal exposure. If these are applied properly with a strong emphasis on adherence, excellent results can be achieved.

Bioavailability of Clindamycin From a New Clindamycin Phosphate 1.2%-Benzoyl Peroxide 3% Combination Gel

A new topical fixed-dose combination product containing clindamycin (1%, formulated as 1.2% clindamycin phosphate, CLNP 1.2%) with low strength (3%) benzoyl peroxide (BPO) in a methylparaben-free gel vehicle (CLNP 1.2%-BPO 3%-MPF) has been developed for the treatment of acne. The objective of this study was to determine the relative bioavailability of clindamycin and clindamycin sulfoxide from CLNP 1.2%-BPO 3%-MPF compared with clindamycin phosphate 1.2%-BPO 5% in a methylparaben-preserved gel vehicle (CLNP 1.2%-BPO 5%-MP) and clindamycin phosphate 1.2%-BPO 5% in a methylparaben-free gel vehicle (CLNP 1.2%-BPO 5%-MPF), and to determine whether exposure is affected by BPO concentration (3% vs. 5%) when applied topically. Seventy-two subjects with moderate-severe acne were randomized to receive CLNP 1.2%-BPO 3%-MPF, CLNP 1.2%-BPO 5%-MP, or CLNP 1.2%-BPO 5%-MPF in a 5-day, open-label, and parallel-group study. Cmax and AUC values for clindamycin were highest for CLNP 1.2%-BPO 5%-MP, followed by CLNP 1.2%-BPO 3%-MPF and CLNP 1.2%-BPO 5%-MPF, but differences were not statistically significant. Systemic exposure to clindamycin and clindamycin sulfoxide was low and comparable between the formulations. Results indicate that differences in BPO concentration do not influence clindamycin bioavailability.

[Acne therapy in pregnancy]

Acne should be treated during pregnancy to prevent worsening, scarring, secondary infection or psychological impairment of the mother. Safe products must be chosen. Systemic tetracycline, doxycycline, minocycline or isotretinoin can not be used. Topical benzoyl peroxide or topical azelaic acid are safe therapeutic options. According to the guidelines, systemic corticosteroids or systemic erythromycin (the latter not in lactation) can be employed beginning in the second trimester for severe flares of acne and should be started in cooperation with the patient's gynecologist. Oral zinc is another option, but not for longer than 3 months. Accessory cosmetic measures may be useful, including mechanical peeling or chemical peeling with glycolic or alpha-hydroxy-acids. In contrast, salicylic acid, trichloracetic acid or phenol peels should not be performed in pregnancy. Camouflage makeup can clearly lower the psychological stress.

Adapalene 0.1%/benzoyl peroxide 2.5% gel: a review of its use in the treatment of acne vulgaris in patients aged ≥ 12 years

Adapalene 0.1%/benzoyl peroxide 2.5% gel (Epiduo™, Tactuo™) is the only fixed-dose combination product available that combines a topical retinoid with benzoyl peroxide; it targets three of the four main pathophysiologic factors in acne. This article reviews the therapeutic efficacy and tolerability of topical adapalene 0.1%/benzoyl peroxide 2.5% gel in the treatment of patients aged ≥ 12 years with acne vulgaris, as well as summarizing its pharmacologic properties. In three 12-week trials in patients aged ≥ 12 years with moderate acne, success rates were significantly higher with adapalene 0.1%/benzoyl peroxide 2.5% gel than with adapalene 0.1% gel or benzoyl peroxide 2.5% gel alone, and combination therapy had an earlier onset of action. In addition, significantly greater reductions in total, inflammatory, and noninflammatory lesion counts were seen in patients receiving adapalene 0.1%/benzoyl peroxide 2.5% gel than in those receiving adapalene 0.1% gel or benzoyl peroxide 2.5% gel alone. Adapalene 0.1%/benzoyl peroxide 2.5% gel did not significantly differ from clindamycin 1%/benzoyl peroxide 5% gel in terms of the reduction in the inflammatory, noninflammatory, or total lesion counts in patients with mild to moderate acne, according to the results of a 12-week trial. Twelve-week studies showed that topical adapalene 0.1%/benzoyl peroxide 2.5% gel in combination with oral lymecycline was more effective than oral lymecycline alone in patients with moderate to severe acne, and topical adapalene 0.1%/benzoyl peroxide 2.5% gel in combination with oral doxycycline hyclate was more effective than oral doxycycline hyclate alone in patients with severe acne. In patients with severe acne who responded to 12 weeks' therapy with topical adapalene 0.1%/benzoyl peroxide 2.5% gel plus oral doxycycline hyclate or oral doxycycline hyclate alone, an additional 6 months' therapy with adapalene 0.1%/benzoyl peroxide 2.5% gel was more effective than vehicle gel at maintaining response, with further improvement seen in adapalene 0.1%/benzoyl peroxide 2.5% gel recipients. A noncomparative study also demonstrated the efficacy of 12 months' therapy with adapalene 0.1%/benzoyl peroxide 2.5% gel in patients with acne vulgaris. Topical adapalene 0.1%/benzoyl peroxide 2.5% gel was generally well tolerated in patients with acne. In 12-week trials, the most commonly occurring treatment-related adverse events included erythema, scaling, dryness, and stinging/burning; these dermatologic treatment-related adverse events were usually of mild to moderate severity, occurred early in the course of treatment, and resolved without residual effects. Topical adapalene 0.1%/benzoyl peroxide 2.5% gel was generally well tolerated in the longer term, with dry skin being the most commonly occurring treatment-related adverse event over 12 months of treatment. In conclusion, adapalene 0.1%/benzoyl peroxide 2.5% gel is a valuable agent for the first-line treatment of acne vulgaris.

Comparison of a chlorhexidine and a benzoyl peroxide shampoo as sole treatment in canine superficial pyoderma

The clinical and antibacterial efficacy of two shampoos used as a sole antibacterial treatment in dogs with superficial pyoderma were investigated and compared. In a randomised, partially blinded study, a 3 per cent chlorhexidine gluconate shampoo (Chlorhex 3; Leo Animal Health) was compared against a 2.5 per cent benzoyl peroxide shampoo (Paxcutol; Virbac) in 22 dogs with superficial pyoderma. Dogs were washed two to three times weekly with a 10-minute contact time over 21 days. Clinical scores and bacterial counts were assessed on days 1, 8 and 22 and compared within and between treatment groups; overall response was assessed at the end of the study. Twenty dogs completed the study; 15 (68.2 per cent) showed an overall clinical improvement and the clinical signs resolved in three chlorhexidine-treated dogs. In the chlorhexidine-treated group, scores for papules/pustules (P<0.001), investigator-assessed pruritus (P=0.003), total bacterial counts (P=0.003) and counts for coagulase-positive staphylococci (P=0.003) were reduced after three weeks. Scores and bacterial counts did not vary significantly in the benzoyl peroxide-treated group.

A comparative evaluation of in vitro skin sensitisation tests: the human cell-line activation test (h-CLAT) versus the local lymph node assay (LLNA)

We previously developed the human cell-line activation test (h-CLAT) in vitro skin sensitisation test, based on our reported finding that a 24-hour exposure of THP-1 cells (a human monocytic leukaemia cell line) to sensitisers is sufficient to induce the augmented expression of CD86 and CD54. The aim of this study is to confirm the predictive value of h-CLAT for skin sensitisation activity by employing a larger number of test chemicals. One hundred chemicals were selected, according to their categorisation in the local lymph node assay (LLNA), as being: extreme, strong, moderate and weak sensitisers, and non-sensitisers. The correlation of the h-CLAT results with the LLNA results was 84%. There were some false negatives (e.g. benzoyl peroxide, hexyl cinnamic aldehyde) and some false positives (e.g. 1-bromobutane, diethylphthalate). Eight out of the 9 false negatives (89%) were water-insoluble chemicals. The h-CLAT could positively predict not only extreme and strong sensitisers, but also moderate and weak sensitisers, though the detection rates of weak sensitisers and non-sensitisers were comparatively low. Some sensitisers enhanced both CD86 and CD54 levels, and some enhanced the level of only one of them. The use of the combination of CD86 and CD54 induction as a positive indicator, improved the accuracy of the test. In conclusion, the h-CLAT is expected to be a useful cell-based in vitro method for predicting skin sensitisation potential.

The topical delivery of benzoyl peroxide using elegant dynamic hydrofluoroalkane foams

Formulating benzoyl peroxide (BPO) in an effective topical product is challenging due to its poor water solubility and chemical instability, but delivering BPO using elegant foams is an attractive solution to this problem. The aim of this work was to investigate how nanoparticle properties influence BPO release and permeation when administrated using dynamic hydrofluoroalkane foams. Lipid (LN, approximately 50 nm) and polymeric (PN, approximately 350 nm) nanoparticles were produced and loaded into topical foams. Drug release and permeation was measured using ultrafiltration and Franz cells studies, respectively. No BPO release was detected when the nanoparticles were stored in the aqueous solvent, but upon administration to silicone membrane the pluronic surfactant-induced LN swelling and BPO delivery (35.7 +/- 3.8 microg cm(-2) h(-1)). In the same situation the PN aggregated with a delivery rate of 2.5 +/- 0.2 microg cm(-2) h(-1). Surprisingly the aqueous nanosuspensions delivered BPO at an equivalent rate to the foams despite the poor drug solubility in the dispersing medium presumably due to ultra-rapid BPO solubilization kinetics of the drug in water. The delivery of BPO from the foams (0.1% BPO) was superior compared to the commercial products (5% BPO), but further testing in human skin is required prior to clinical use.

A current review of topical benzoyl peroxide: new perspectives on formulation and utilization

Benzoyl peroxide (BPO) is the most widely used topical acne treatment, with significant antibacterial, antikeratolytic, and comedolytic activity. It has been shown to be extremely effective as monotherapy and in combination with antibiotics or retinoids for managing comedonal and inflammatory acne lesions. As numerous clinical studies have shown, the combination of BPO plus a topical antibiotic is not only more effective but also is often better tolerated than either agent alone. Unlike antibiotics, no bacterial resistance has been noted. Adding BPO to any long-term antibiotic regimen in acne is generally recommended to help reduce populations of drug-resistant variants. Although effective combinations of BPO and antibiotics or retinoids are used, BPO monotherapy can also be extremely effective in treating mild to moderate acne with no resistance issues.

A randomized, single-blind comparison of topical clindamycin + benzoyl peroxide (Duac) and erythromycin + zinc acetate (Zineryt) in the treatment of mild to moderate facial acne vulgaris

BACKGROUND

Antibiotics are often combined with other agents to provide topical acne treatments that are effective against both inflammatory and non-inflammatory lesions and minimize the development of antibiotic resistance.

OBJECTIVES

To compare the clinical effectiveness of two combination treatments for facial acne: a ready mixed, once daily gel containing clindamycin phosphate (1%) plus benzoyl peroxide (5%) (CDP + BPO) and a twice daily solution of erythromycin (4%) plus zinc acetate (1.2%) (ERY + Zn).

METHODS/PATIENTS

In this assessor-blind, randomized study, 73 patients were treated with CDP + BPO once daily and 75 patients with ERY + Zn twice daily. The treatment period was 12 weeks and lesion counts and global improvement were assessed at weeks 1, 2, 4, 8 and 12.

RESULTS

CDP + BPO showed an earlier onset of action with a faster significant reduction in total lesion counts than ERY + Zn. The proportion of patients with at least a 30% improvement in non-inflammatory lesions at week 1 was 31.5% for CDP + BPO and 17.3% for ERY + Zn; the corresponding percentages for inflammatory lesions were 39.7% and 29.3%. A difference was also observed at week 2 (53.4% vs. 36.0% for non-inflammatory lesions and 72.6% vs. 53.3% for inflammatory lesions). The trend in favour of CDP + BPO, although less marked, continued to the end of the study, with reductions in the total lesion count at endpoint of 69.8% for CDP + BPO group and 64.5% for ERY + Zn group. Both treatments were well tolerated.

CONCLUSIONS

CDP + BPO and ERY + Zn are effective treatments for acne but CDP + BPO has an earlier onset of action that should improve patient compliance.

The combination formulation of clindamycin 1% plus benzoyl peroxide 5% versus 3 different formulations of topical clindamycin alone in the reduction of Propionibacterium acnes. An in vivo comparative study

BACKGROUND

Isolates of Propionibacterium acnes resistant to one or more anti-acne antibiotics (most commonly erythromycin) are being increasingly reported, and the emergence of resistant strains can be associated with therapeutic failure of topical treatment.

OBJECTIVE

Comparison of the in vivo effectiveness of the combination of clindamycin 1% plus benzoyl peroxide 5% in a gel formulation to that of each of 3 clindamycin 1% preparations (gel, lotion, and solution) with respect to reduction in counts of P. acnes cultured from the foreheads of healthy volunteers.

METHODS

The effects of treatment with the 4 study drugs were compared in an open-label study. Cultures were collected before, after 1 week and after 2 weeks of treatment.

RESULTS

Treatment with the combination formulation resulted in a 99.8% (> 2 logs) reduction in total propionibacterial numbers after 1 week of therapy compared with 30 to 62% (< 1 log) decreases for the different formulations of topical clindamycin alone. By the end of week 2, the combination had decreased P. acnes counts by more than 99.9% (> 3 logs) relative to reductions of from 88 to 95% (< or > 1 log) for the single agent formulations.

CONCLUSIONS

Under the conditions of the present study, the combination of clindamycin 1% plus benzoyl peroxide 5% gel produced more rapid and highly significant reductions in P. acnes compared with formulations containing clindamycin alone.

Comparison of the efficacy and safety of a combination topical gel formulation of benzoyl peroxide and clindamycin with benzoyl peroxide, clindamycin and vehicle gel in the treatments of acne vulgaris

BACKGROUND

Topical clindamycin and benzoyl peroxide have each demonstrated clinical efficacy in the treatment of acne vulgaris. When used in combination, they promise greater efficacy than either individual agent used alone and the combined use of benzoyl peroxide with topical antibacterial has been shown to decrease the emergence of antibacterial resistant species.

OBJECTIVE

The objective was to determine the efficacy and safety of a combination benzoyl peroxide plus clindamycin in a gel formulation compared with each of its 2 active constituents in gel vehicle, and gel vehicle given alone in the treatment of acne vulgaris.

METHODS

In this 10-week, multicenter, double-blind trial, 480 patients with moderate to moderately severe acne were randomized to receive twice-daily treatment with 5% benzoyl peroxide plus 1% clindamycin, 5% benzoyl peroxide, 1% clindamycin, or vehicle.

RESULTS

Significantly greater reductions in the number of inflammatory and total lesions were demonstrated in patients using combination therapy compared with those using any of its 3 individual components. Likewise, both physicians' and patients' global evaluations showed significantly greater improvements with the combination therapy than with its individual components. The most frequent adverse effect, dry skin, occurred to a similar extent in the combination and benzoyl peroxide treatment groups.

CONCLUSION

The improved efficacy obtained with the combination therapy was accompanied by a tolerability profile similar to that of benzoyl peroxide alone, making this new combination product an alternative antimicrobial therapy for acne vulgaris.

The efficacy and safety of a combination benzoyl peroxide/clindamycin topical gel compared with benzoyl peroxide alone and a benzoyl peroxide/erythromycin combination product

BACKGROUND

Topical clindamycin and benzoyl peroxide have each demonstrated clinical efficacy in the treatment of acne vulgaris. When used in tandem, they promise greater efficacy than either individual agent through their antibacterial and anti-inflammatory effects.

OBJECTIVE

To determine the efficacy and safety of combination benzoyl peroxide/ clindamycin compared with benzoyl peroxide or benzoyl peroxide/erythromycin in the treatment of acne.

METHODS

In this randomized, 10-week, multicenter, single-blind trial, 492 patients with moderate to moderately severe acne were treated twice daily with 5% benzoyl peroxide/1% clindamycin, 5% benzoyl peroxide, or 5% benzoyl peroxide/3% erythromycin and assessed every 2 weeks.

RESULTS

Compared with benzoyl peroxide, benzoyl peroxide/clindamycin demonstrated significantly greater reductions in inflammatory lesions (p = 0.04) and significantly greater overall improvement as assessed by physicians (p < or = 0.04) and patients (p < 0.001). Benzoyl peroxide/clindamycin demonstrated a nonsignificant trend for greater efficacy compared to benzoyl peroxide/erythromycin. Dry skin was the most frequent (< or = 7.3%) adverse event with all three therapies.

CONCLUSION

Benzoyl peroxide/clindamycin demonstrated improved efficacy and similar tolerability; to benzoyl peroxide used alone and was similar to benzoyl peroxide/ erythromycin, making this combination product an effective alternative antimicrobial therapy for acne.

Benzoyl peroxide cytotoxicity evaluated in vitro with the human keratinocyte cell line, RHEK-1

The human keratinocyte cell line, RHEK-1, was used to evaluate the cytotoxicity of benzoyl peroxide (BZP). As determined with the neutral red (NR) cytotoxicity assay, the 24-h midpoint (NR50) toxicity values, in mM, were 0.11 for BZP and 29.5 for benzoic acid, the stable metabolite of BZP. Irreversible cytotoxicity occurred after a 1-h exposure to 0.15 mM BZP and greater. When exposed to BZP for 7 days, a lag in growth kinetics was first observed at 0.06 mM BZP. Damage to the integrity of the plasma membrane was evident, as leakage of lactic acid dehydrogenase occurred during a 4-h exposure to BZP at 0.05 mM and greater. Intracellular membranes were also affected, as extensive vacuolization, initially perinuclear but then spreading throughout the cytoplasm, was noted in BZP-stressed cells. The generation of reactive free radicals from BZP was suggested by the following: the intracellular content of glutathione was lowered in cells exposed to BZP; cells pretreated with the glutathione-depleting agent, chlorodinitrobenzene, were hypersensitive to a subsequent challenge with BZP; lipid peroxidation by BZP was inducible in the presence of Fe2+; and cells previously maintained in a medium amended with vitamin E, an antioxidant, were more resistant to BZP, showed less lipid peroxidation in the presence of BZP+Fe2+ and did not develop the extensive intracellular vacuolization as compared to non-vitamin E maintained cells.

Controlled release of benzoyl peroxide from a porous microsphere polymeric system can reduce topical irritancy

Skin absorption of benzoyl peroxide from a topical lotion containing freely dispersed drug was compared with that from the same lotion in which the drug was entrapped in a controlled-release styrene-divinylbenzene polymer system. In an in vitro diffusion system, statistically significant (p = 0.01) differences were found in the content of benzoyl peroxide in excised human skin and in percutaneous absorption. In vivo, significantly (p = 0.002) less benzoyl peroxide was absorbed through rhesus monkey skin from the polymeric system. This controlled release of benzoyl peroxide to skin can alter the dose relation that exists between efficacy and skin irritation. Corresponding studies showed reduced skin irritation in cumulative irritancy studies in rabbits and human beings, whereas in vivo human antimicrobial efficacy studies showed that application of the formulations containing entrapped benzoyl peroxide significantly reduced counts of Propionibacterium acnes (p less than 0.001) and aerobic bacteria (p less than 0.001) and the free fatty acid/triglyceride ratio in skin lipids. These findings support the hypothesis that, at least for this drug, controlled topical delivery can enhance safety without sacrificing efficacy.

Use of oral and topical agents for acne in pregnancy

Dermatologists frequently are consulted by a pregnant patient or a woman of childbearing age who desires acne therapy. Because there are no published studies in which women took acne medications throughout pregnancy, information about safety must be obtained indirectly from studies in which the agents were taken for another indication during some portion of pregnancy. Oral tetracycline is associated with maternal liver toxicity and deciduous tooth staining in the infant, and tetracycline occasionally has been associated with other congenital anomalies. Maternal isotretinoin ingestion is associated with major craniofacial and cardiac deformities, as well as other congenital anomalies. Erythromycin, however, appears to be safe. Topical acne medications never have been implicated as a cause of fetal deformities in human beings. Dermatologists should be aware of potential toxic and teratogenic effects of acne medicines before prescribing them to women of childbearing age. Prompt reporting of adverse effects is encouraged.

The bioavailability of dermatological and other topically administered drugs

The literature addressing determination of the bioavailability of dermatological and other topically administered drugs has been reviewed. The various methods employed, their advantages and drawbacks, have been identified and evaluated. The state of the art and the success of topical bioavailability assessment are discussed in the light of the information presented. It is concluded that, although current methodology ensures the responsible use of topical medicaments, the techniques are, on the whole, quantitatively inadequate. A number of recommendations are proposed as possible improvements to the approaches now undertaken, and specific measurements for drugs in different therapeutic categories are suggested. The ultimate objective of this survey is to catalyze the establishment of straightforward, objective, quantitative, and reproducible methods to evaluate topical bioavailability and to reduce significantly, thereby, the incidence of bioinequivalence and pharmacological inactivity observed following drug dosing to the skin.

Initiation and promotion in experimental oral carcinogenesis

A subthreshold dose of 0.1% DMBA in oil applied to hamster buccal pouch three times a week for 10 weeks did not result in the development of carcinoma in up to 25 weeks from the start of the experiment. However, if the subthreshold dose of DMBA was followed by 6 weeks of no treatment and six weeks of 40% benzoyl peroxide treatment, carcinomas developed rapidly. Both benzoyl peroxide and its acetone solvent are noncarcinogenic. An experiment carried out on sixty-six young adult male and female Syrian hamsters demonstrated these results, using appropriate controls.

Benzoyl peroxide: percutaneous penetration and metabolic disposition. II. Effect of concentration

The effect of drug concentrations of 2.5%, 5%, and 10% upon the transepidermal penetration of 14C-benzoyl peroxide in a lotion vehicle was assessed in excised human skin and in vivo in the rhesus monkey. In vitro, penetration of benzoyl peroxide was concentration-dependent, both as to rate and to amount, as measured by the hourly recovery of the metabolite, benzoic acid, from the dermal side of the model. In vivo, the higher the concentration of benzoyl peroxide applied, the greater the amount absorbed, as indicated by the urinary excretion of 14C-benzoic acid. Metabolic disposition of benzoyl peroxide, in turn, was unaffected by drug concentration. In all instances, the benzoyl peroxide absorbed was excreted rapidly in urine as benzoic acid; no hippuric acid was detected at any time. We conclude that (1) use of the excised human skin model for this compound can provide useful data in studies of the effects of vehicle and concentration on topical drug delivery, (2) the transepidermal delivery of benzoyl peroxide, but not its metabolic disposition, is concentration-dependent, and (3) the renal clearance of the systemically absorbed drug is so rapid that it precludes passage through the liver--therefore, no systemic toxicity due to drug accumulation can be expected.

Percutaneous absorption, blood levels, and urinary excretion of resorcinol applied topically in humans

The absorption and metabolic disposition of 2% resorcinol applied topically in a hydroalcoholic vehicle was determined in three human subjects. The drug penetrated the skin at a rate of 0.37 micrograms/cm2/hour. After 2 weeks of bid application of 800 mg resorcinol to about 30% of body surface of each subject, an average of 1.64% of the dosage was being excreted in 24-hour urine specimens as the glucuronide or as the sulfate conjugate. There was no resorcinol in blood drawn at weeks 1, 2, 3, and 4, or nor were there any abnormalities in thyroid function or blood chemistries at weeks 2, 3, and 4. Resorcinol (2%) appears safe for topical use in humans.