Overview

What are yeast infections?

Yeast is a type of fungus that typically causes no harm to you, living on your skin and inside your body, such as in the mouth, throat, gut and in the vagina. However, excessive yeast growth can result in a yeast infection. (CDC, John Hopkins Medicine)

Why are antifungal medications important?

Antifungal medications are used to treat fungal infections. The most common fungal infections are treated with antifungal medications. These are known as dermatophytic fungal infections, which affect the skin, hair and nails.¹ (NHS)

Types of yeast infections

Skin yeast conditions (candidiasis)

Skin candidiasis typically occurs where your skin rubs, such as between skin folds, due to heat and moisture from your skin rubbing causing inflammation. (NICE)

Vaginal yeast conditions (candidiasis)

Vaginal candidiasis is caused by a type of yeast known as Candida, which usually resides on your skin, in your mouth and throat, vagina and gut without causing any infection. However, if the conditions inside your vagina change, this can make your vagina more susceptible to Candida growth, resulting in a vaginal yeast infection, which you may commonly see referred to as thrush or candidiasis. Both of which are the same fungal infection. (CDC)

There are more causes and risk factors for vaginal candidiasis than skin candidiasis, which include the following:

• Changes in hormones
• Changes in medicines
• Changes in  your immune system
• If you use hormonal contraceptives
• If you are pregnant
• If you have diabetes
• If you are immunocompromised, this can be caused by chemotherapy or if you have HIV for example
• If you are currently on a course of antibiotics or have recently finished a course of antibiotics

These changes within your body can create an environment that promotes the overgrowth of candida inside your vagina. Vaginal candidiasis has symptoms to look out for, including the following:

• Burning and itching sensation
• Pain when you urinate
• Having an abnormal vaginal discharge
• Experiencing pain during sex
• (CDC)

Mouth candidiasis

Candida usually resides in your mouth, throat and oesophagus without causing an infection. However, if Candida multiplies exponentially, this can cause an overgrowth of the fungus and result in an infection of the mouth. This can be identified by the following symptoms:

• Your mouth looks red and sore
• Loss of taste
• Cotton-like feeling in your mouth
• White patches visible on your tongue, inside of your cheeks and on the roof of your mouth
• Pain whilst eating
• Pain when you swallow

Mouth candidiasis can be caused by the following:

• Wearing a denture
• Having diabetes
• Being on a course of antibiotics or corticosteroids
• Smoking
• Having cancer
• Having an autoimmune condition such as HIV or AIDS
• (CDC)

 Common antifungal medications

Antifungal medications to treat yeast infections are typically azole medications, and some of these medications will be discussed below

Over-the-counter options

Clotrimazole

Clotrimazole is an antifungal medication that is synthetic and is useful in treating a wide spectrum of fungal infections from mouth candidiasis and vaginal candidiasis to fungal infections of the skin such as athlete’s foot and ringworm to name just a couple.²

However, this raises the question, how does clotrimazole treat these fungal infections?

Well, firstly we must look at a fungal cell, which has an outer layer, protecting what is inside the fungal cell from the outside environment. This is known as a cell membrane, which has many roles, including acting as a selective barrier to what can enter and exit the fungal cell. Clotrimazole prevents a molecule known as ergosterol from being made, which is a necessary part of a fungal cell’s membrane, and as a result, this compromises the cell membrane and results in cell death.²

Miconazole

Miconazole is another broad-spectrum antifungal medicabroad-spectrumets a range of fungi that cause infection. Similar to clotrimazole it is synthetic, and treats fungal infections in the same manner by preventing ergosterol from being made and compromising the fungal cell wall. This results in fungal cell death.³

Prescription medications

Fluconazole

Fluconazole is used to treat various forms of yeast infections (candidiasis), including vaginal, oropharyngeal and oesophagal candidiasis. Fluconazole is also used to treat systemic candida infections which affect usually sterile body fluids, such as your blood. This includes candidemia, cryptococcus meningitis and pneumonia.  Fluconazole acts similarly to the two previous antifungal medications, by using a mechanism that prevents the synthesis of ergosterol. A crucial component of a fungal cell’s cell membrane.⁴

Ketoconazole

Ketoconazole is an antifungal medication used to treat systemic fungal infections and fungal infections which affect your skin. Ketoconazole works by preventing the synthesis of ergosterol which is needed to keep the integrity of the fungal cell’s cell membrane.⁵

Administration and usage guidelines

Dosage forms

Clotrimazole

Clotrimazole is available in the following dosage forms:

• Oral tablets: these should be allowed to dissolve in the mouth and are not to be chewed. For adults and children aged 3 and over one 10mhg lozenge should be completely dissolved in the mouth. This should be repeated 5 times a day for at least 14 days to treat candidiasis (Mayo Clinic)
• Vaginal tablets: these are inserted intravaginally and are known as pessaries. They must be allowed to completely dissolve inside your vagina and should therefore be inserted as far as you can into your vagina. These are inserted before bedtime. Pessaries come in 3 different strengths: 100mg (where you use 1 pessary every night for 6 nights or use 2 every night for 3 nights), 200mg (where you use 1 pessary every night for 3 nights), 500mg (where 1 pessary is used for 1 night) (NHS)
• Vaginal creams: you may be advised to use one applicatorful of 1% cream or two applicatorfuls of 2%. For the 1%, the duration of treatment should be 7 days, whereas for the 2% cream the duration of treatment should be 3 days. Creams are applied at bedtime. External cream application may be advised if you have extra-vaginal symptoms
• Topical cream/lotion/spray: the strength of this is typically 1% and should be applied to the affected area. These creams/lotions and sprays are not to be used vaginally. This should be applied 2-3 times a day for approximately 2 weeks.² (NHS)

Miconazole

Miconazole is available in the following dosage forms:

• Cutaneous cream (2%): apply twice daily for 10 days until the skin lesions have fully healed
• Cutaneous powder (2%): this should be applied twice daily for 10 days until skin lesions have fully healed
• Nail polish: under the nail application to be applied 1-2 times a day for treatment of fungal nail infection
• Oral gel: 2.5ml of the gel to be taken 4 times a day, at least 7 days after the lesions have cleared or you have been relieved of your symptoms of oral candidiasis
• Spray: to be applied 1-2 times a day 3 inches away from the skin to treat fungal nail infection

(BNF)

Fluconazole

The following are dosage forms for fluconazole:

• Fluconazole capsules: for oral thrush take a 50mg tablet once a day for 7-14 days. For vaginal thrush take a 150mg tablet as a single dose.
• Fluconazole liquid comes in two different strengths: 50mg and 200mg, and can be taken as an alternative to capsules.

Please note that the duration of treatment is dependent on the infection and whether or not it keeps on returning. (NHS)

Ketoconazole

The following dosage forms are available for ketoconazole:

• Vaginal cream: applied daily to the anogenital area 1-2 times  for vaginal candidiasis
• Topical cream: apply to the infected area 1-2 times daily
• Oral tablets: for adults take a 200mg dose once a day

(BNF, Mayo Clinic)

Potential side effects and precautions

Common side effects

Clotrimazole

• When applying the medication your skin is red or you experience a burning sensation (NHS)

Miconazole

• Headache and nausea
• Diarrhea
• Changes in taste
• Dry mouth
• Toothache
• Itchiness
• Gums are painful, red and swollen

(Mayo Clinic)

Fluconazole

• Nausea and vomiting
• Stomach pain
• Headache
• Rash

(NHS)

Ketoconazole

• Itching or redness on the skin when it is applied
• A burning sensation when it is applied

Rare but adverse side effects

Clotrimazole

• Having an allergic reaction, signs include your lips, mouth and tongue becoming swollen and having difficulties breathing (NHS)

Miconazole

• Shortness of breath
• Pale skin
• Black tar-like stool
• Ulcers in the mouth

(Mayo Clinic)

Fluconazole

• Pale wee and dark poo or the whites of your eyes turning yellow, indications of liver problems (call 111 immediately)
• Serious allergic reaction- anaphylaxis  (call 111 immediately)
• Bruising easily- a sign of a blood disorder (call 111 immediately)
• Having a fast or irregular heartbeat (call 111 immediately)

Ketoconazole

• Anaphylaxis, serious allergic reaction (call 111 immediately)

Precautions for special populations, those who are pregnant or have liver disease

Miconazole and clotrimazole have only been found in one study to slightly increase the chance of miscarriage. However, other studies have not found this to be the case. However, you should always consult with your healthcare provider before starting any medication when pregnant.⁶

Fluconazole may be recommended if other treatments have not worked to treat your fungal infection. (NHS) In addition, ketoconazole can also be used if you are pregnant, including use in shampoo form. (NHS)

However, care should be taken if you have liver disease with azoles being found to be associated with acute liver failure occurrences.⁷ However, you should always consult with your healthcare practitioner first as they can best advise you.

Interactions and contraindications

Drug-drug interactions

Administering any of the following drugs, in conjunction with an azole medication. These drugs include:

• Phenytoin
• Rifampicin
• Isoniazid
• Ritonavir
• Phenobarbital
• Efavirenz

These drugs can induce the activation of an enzyme known as CYP3A4, which in turn can cause azole antifungal medications to become metabolized, meaning that they do not have an antifungal effect.⁸

Summary

• Fungal infections are caused by an overgrowth of fungal cells
• Fungal infections are treated with antifungal medication
• Yeast infections (candidiasis) can be treated with a group of antifungal medications known as the azoles
• Azoles can be applied via creams topically or intravaginally, via oral capsules, liquids, sprays, nail polish
• Different azoles have different side effects and may cause adverse side effects such as anaphylaxis
• You should consult with your healthcare provider before taking azoles if you have liver disease or are pregnant
• Different drugs may interact with azoles so please consult with your healthcare provider if you are on other medication