US Pharm. 2010;35(8):10-15.
Pharmacists are often asked about treatment of minor medical conditions such as tinea pedis, commonly known as athlete’s foot. At times, patients may need confirmation that they actually have the condition. For this reason, it is important for the pharmacist to be able to recognize tinea pedis and provide appropriate advice in treating it and preventing its recurrence.
Prevalence of Tinea Pedis
The reported prevalence of tinea pedis is dependent on the sampling group chosen, but it is thought to be the most common fungal pathogen.1 In one survey, it was found to affect as many as one-quarter of those visiting a dermatology clinic for reasons unrelated to fungi, and it has been reported to be present in 70% of adults.2,3 Many patients do not know that they suffer from the condition, perhaps attributing their symptoms to other causes (e.g., dermatitis).
Etiology of Tinea Pedis
Dermatophytes are a class of keratinophilic cutaneous fungal organisms that subsist on the stratum corneum, the dead layer of skin, as well as the hair, fingernails, and toenails.3 These mycoses are usually unable to exist on unkeratinized, living layers of skin and mucous membrane. Like other dermatophytes, the organisms responsible for tinea pedis survive optimally in warm, moist areas, such as intertriginous skin (areas that are often or constantly in contact with other skin). Thus, this common dermatophytic skin infection often attacks the areas between the toes. Specific causal organisms include Trichophyton rubrum (responsible for 71.2% of cases), Trichophyton tonsurans (6.9%), Trichophyton mentagrophytes (5.5%), Microsporum canis (4.5%), and Epidermophyton floccosum (1.3%).4,5
Epidemiology of Tinea Pedis
Tinea pedis is more common in adults aged 15 to 40 years than other age groups, and it also prefers males over females.3,6,7 A major epidemiologic risk factor is use of communal bathing facilities, making those who use them prime targets. Shared bathtubs and showers are common in locker rooms, summer camps, college dormitories, municipal swimming pools, gyms, sports clubs, steam rooms, and boarding schools.3,8 The common name of the condition (athlete’s foot) reflects the general awareness that it occurs more frequently in such groups.
A further epidemiologic factor involves choice of footwear. Some who walk on contaminated surfaces escape the condition, while others experience its uncomfortable symptoms. After the fungus reaches target tissues, it requires optimal warmth and humidity to fully begin to infect the host. Wearing socks and shoes creates an ideal environment that is most conducive to fungal growth, and sneakers have been found to be an independent risk factor for acquiring tinea pedis.8 Conversely, going barefoot or wearing sandals allows the foot to dry and cool off, inhibiting tinea pedis pathogens.
Research has also identified owning a pet as a risk factor for tinea pedis.8 In these cases, the pet carries fungal organisms (e.g., M canis) that are capable of existing on human tissues, and normal human-pet interactions allow transfer to the owner. Many owners deny that their pet is the cause, believing that an infected pet will carry visible evidence of infection, such as large spots where its fur is denuded. However, in most cases, the infected pet retains its fur, and owners remain unaware that their pets are carriers of these zoophilic organisms until they contract the infection from them.
Manifestations of Tinea Pedis
When pharmacists field questions about possible tinea pedis, it is critical to be aware of the condition’s visible signs and symptoms in order to fully and capably assist the patient. With the patient’s consent, the pharmacist may be able to view the foot and ankle, facilitating recognition of the condition.
Tinea pedis most often begins on the small toe, or in the groove between the fourth and fifth toes, so these areas should be examined first.3 The reason for this geographic predilection is that the fifth toe is most likely of all to be overcrowded in tight shoes or sneakers, and its continued close proximity to the fourth toe does not allow the interdigital toe web to dry as thoroughly as other surfaces of the foot. Moisture accumulation and maceration present ideal conditions for growth of the organisms following implantation. From that common starting point, tinea pedis is able to branch out and assume several forms.
The most common category is known as interdigital tinea pedis.3,9 In this type, the skin between the patient’s toes (most often the fourth and fifth) begins to itch and break down. Fissures develop, with accompanying maceration to the point of a boggy appearance, increased whitening and thickening, intense pruritus and burning, and the development of a foul odor due to bacterial overgrowth in the open wounds.3,10
Tinea pedis may present in the second form, known as acute vesiculobullous infection. Foul odor and intense pruritus are also present.3,10 The lesions include vesicles and pustules; inflammation and fissuring are also prominent. Patients may be virtually disabled by the symptoms.
The third form of tinea pedis is the moccasin type, most often caused by anthropophilic fungi that are passed from person-to-person. The patient notices a fine scale over the plantar surface, but there are no vesicles, and there may be no symptoms. The name is justified, as the preferential locations (plantar surface, heel, and sides of the foot) are those covered by a moccasin. This form is often chronic, persisting for many years and recurring each summer as conditions (e.g., sweating) become ideal for its emergence.
The pharmacist should also inquire whether one or both hands have begun to appear red, dry, or scaly.3 This is common in patients who habitually attempt to relieve the pruritus of tinea pedis by scratching, transferring the tinea to the hand. The condition, known as tinea manuum, may be present on both hands, but is more common on just one hand, a condition known as “two-foot, one-hand” syndrome. Nonprescription products may not be effective on the hand, as tinea manuum is not an FDA-approved indication.
The pharmacist will often note that tinea pedis is accompanied by toenail infection, a condition known as tinea unguium or onychomycosis.11 Toenails infected with tinea often appear brittle, opaque, yellow, thickened, and crumbled. Infection of the nails may be the reason for persistent tinea pedis, as the organisms remain there to spread out when conditions permit.12 Nonprescription products are unable to treat this condition. Thus, the patient must be urged to see a physician for prescription therapy.
Treatment of Tinea Pedis
Tinea pedis may be treated with topical or systemic prescription therapies. Systemic oral medications (e.g., griseofulvin, itraconazole, ketoconazole, terbinafine) carry the possibility of adverse reactions such as diarrhea or skin rash, making the relatively innocuous OTC products an attractive initial therapeutic choice.3,13-15 When recommending nonprescription products, pharmacists should stress the importance of adhering to the regimen, applying the substance as often as directed, and completing the full course of therapy as suggested on the label.
Nonprescription treatment of tinea pedis is categorized into three generations, with succeeding products presenting significant advantages.3,16 The first generation includes clotrimazole (e.g., Cruex Cream, Lotrimin AF Cream); miconazole (e.g., Cruex Spray Powder, Desenex Powder, Lotrimin AF Powder, Micatin Spray Liquid); and tolnaftate (e.g., Lamisil AF Defense Powder, Tinactin Cream and Spray). These are indicated for patients aged 2 years and above.3 The patient is directed to apply the product twice daily, and it must be applied for 4 weeks. The labels state that the products will cure tinea pedis but do not indicate any difference in efficacy for the three subtypes. These imidazole compounds are not fungicidal, as they only interrupt development of the membrane of growing fungal cells. Thus, they are only bacteriostatic, which accounts for their relatively long application time. Of the three compounds in this class, tolnaftate is the sole agent approved for preventing annual recurrences, but patients who experience yearly recurrences have not achieved the promised cure, making more effective products preferable.
The second generation of OTC antifungals for tinea pedis contains two ingredients: topical butenafine and terbinafine.3,16 Butenafine is a synthetic fungistatic/fungicidal benzylamine, and terbinafine is a fungicidal allylamine. These products warrant separate consideration because they promise cures in a shorter time, and they are not safe in patients below the age of 12 years. Butenafine (e.g., Lotrimin Ultra Cream) will cure tinea pedis between the toes (e.g., the interdigital form) in only 1 week if used twice daily or in 4 weeks if the patient uses it only once daily. Thus, the pharmacist should urge the patient to apply the product each morning and at night. Butenafine is not known to be effective if the patient has tinea pedis on the bottom and sides of the feet (i.e., moccasin type). Topical terbinafine (e.g., Lamisil AT Cream, Spray Pump, Solution) will cure tinea pedis between the toes when used twice daily for 1 week. The cream is also labeled to cure tinea pedis on the bottom and sides of the feet when used twice daily for 2 weeks.
The newest generation of nonprescription tinea pedis products contains only one ingredient: terbinafine in a gel dosage form (e.g., Lamisil AT Gel).16 This product can also cure tinea pedis between the toes in patients aged 12 years and above, but it is in a separate class because the gel requires only once-daily application to produce a cure in 1 week. The reason for its enhanced efficacy is a highly lipophilic/keratophilic nature, allowing it to achieve high therapeutic levels that remain for an additional 7 days beyond its initial 7-day application.16
Preventing Tinea Pedis
Pharmacists can provide advice on preventing tinea pedis.3,17 Patients should keep the feet dry and clean, drying them thoroughly (especially between the toes) before putting on socks and shoes. They should go barefoot whenever possible to allow thorough drying and be urged to wear rubber sandals whenever they walk in communal bathing facilities or any location where people have walked with bare feet. If a toenail becomes infected, they must seek immediate care to prevent the spread of infection to the surrounding skin. Finally, if patients develop tinea in another part of the body, they must take great care to prevent transferring it to the foot (e.g., by washing and drying that part of the body with separate cloths).
Identifying Athlete’s Foot
Athlete’s foot, also known as tinea pedis, is a fungal infection that can appear in several forms. Perhaps you have noticed the area between your fourth and fifth toes has become infected, with fissures, cracking, and a wet look and feel, with whitening and/or thickening of the skin. Itching may be so severe that it requires almost constant scratching. There may also be an intense, foul odor.
You may notice that other spots on the foot are involved as well. Perhaps the sole and sides of the foot are affected with small blisters, scaling, swelling, and open cracking. Your toenails appear white or brittle, with crumbling and cracking of the nail. The nail may even lift up from its nail bed. Finally, tinea pedis that is not cured tends to be less intense during the winter and may seem to almost disappear. However, with the beginning of late spring or summer, it may return again and again unless a total cure is achieved.
How Can You Treat Athlete’s Foot?
There are many noninfective conditions that affect the foot, such as psoriasis and poison ivy. If you are unsure whether your problem is athlete’s foot (i.e., symptoms differ markedly from those previously explained), you should visit a physician. Your pharmacist may also be able to recognize the presence of athlete’s foot. Once athlete’s foot is confirmed, you may treat the problem with nonprescription products. Generally, OTC products are safer than prescription products, as they have fewer side effects. Used properly, nonprescription products may also cure athlete’s foot.
Your pharmacist can provide full counseling information on treatment options for athlete’s foot. You must read the labels carefully and follow all directions provided. Some products (e.g., Lotrimin AF Cream, Micatin Spray Liquid, Tinactin Cream) can be used in anyone aged 2 years and above, but they must be used twice daily for 4 weeks to produce a cure.
Another product (Lotrimin Ultra Cream) must only be used in those aged 12 years and above, but it can cure athlete’s foot between the toes in 1 week if used twice daily or in 4 weeks if you choose to use it only once daily. However, it will not cure athlete’s foot on the bottom or sides of the feet, which is known as moccasin type.
Lamisil AT Cream can also cure athlete’s foot in those aged 12 years and above. The spray pump and solution forms only cure the condition between the toes if used twice daily for 1 week, but the cream can also cure the infection on the bottom and sides of the feet when used twice daily for 2 weeks.
A newer product, Lamisil AT Gel, can cure athlete’s foot between the toes of patients aged 12 years and above when used just once daily for 1 week. This presents enhanced convenience in use, as no other product cures this quickly when used only once daily.
With such an array of OTC options available to treat and even cure athlete’s foot, it is always a good idea to ask your pharmacist for a recommendation for the most appropriate product.
REFERENCES
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