A dental student’s guide to…common medications (part two)

medicationsFollowing on from part one exploring common medications dentists may come across, Hannah Hook and Tina Aster look into antifungals and antivirals.

Throughout your dental career it is likely that you will encounter a range of patients presenting with a variety of fungal or viral infections.

You can detect oral manifestations of these infections when carrying out a thorough intra-oral examination. Along with information obtained from a comprehensive medical and pain history.

As with antibiotics, to ensure effective patient management it is useful to know what the available types of antifungals and antivirals are, how they work and when to prescribe them.

Antifungals

Azoles

Examples: Fluconazole, Miconazole.

Mechanism of action: azoles target ergosterol synthesis (Figure 1). Inhibition of the enzyme, which synthesises ergosterol leads to depletion of ergosterol resulting in the formation of a cell membrane with altered structure and function (Ghannoum and Rice, 1999).

Uses: fluconazole is usually the first line of treatment for oral fungal infections, followed by miconazole.

Contraindications: do not prescribe azole antifungals to a patient taking warfarin or statins as this increases their effects.

Polyenes

Examples: Amphotericin B (systemic), Nystatin (topical).

Mechanism of action: polyenes are a type of broad-spectrum antifungals that work by disrupting the cell membrane of the fungus. They do this by binding to ergosterol, a steroid in the cell membrane (Figure 1), which leads to depolarisation of the membrane and an increase in K+ and Na+ permeability. This ultimately results in cell death (Birch and Sibley, 2017).

Uses: Nystatin is commonly prescribed for patients where azole antifungals are contraindicated.

Contraindications: no contraindications listed in the BNF (NICE, 2020).

Antifungal prescribing

The majority of oral fungal infections are caused by yeasts belongings to the genus Candida.

Patients who are undergoing antibiotic therapy, taking systemic or inhaled steroids, on immunosuppressive medication or have endocrine disorders such as diabetes are predisposed to oral fungal infections.

When a patient attends with an oral fungal infection attempt to resolve the infection with local measures first. Whilst the majority of oral fungal infections can be treated in a primary care setting, chronic hyperplastic candidosis, also known as candida leukoplakia, is potentially premalignant and you should therefore refer patients with this condition to a specialist.

Condition Local measures Prescribing
Pseudomembranous Candidosis

 

  • If using corticosteroid inhaler advise patient to rinse mouth with water or brush teeth after use.
Fluconazole capsules

  • 50mg, one daily for seven days.

Miconazole Oromucosal Gel

  • 80g tube, pea-sized amount, four times daily after food
  • Continue use for seven days after lesions have healed.

Nystatin Oral suspension, 100,000 units/ml

  • 30ml, 1ml, four times daily after food.
Erythematous Candidosis

 

Denture Stomatitis
  • Clean dentures thoroughly
  • Leave dentures out at night.
Angular Cheilitis
  • Check to see if dentures are the cause of the infection
  • Decreased occlusal vertical dimension can lead to folding of the corners of the mouth
  • If dentures are a possible cause adjust or remake.
Miconazole cream, 2%

  • 20g tube, apply to angles of the mouth four times daily
  • Continue use for 10 days after lesions have healed.

Sodium Fusidate ointment, 2%

  • 15g tube, apply to angles of the mouth four times daily
  • Use for no longer than 10 days.

Table 2: Antifungal prescribing following guidance from SDCEP and FGDP

Antivirals

Example: Aciclovir

Mechanism of action: when aciclovir enters a cell infected with HSV or VSV, it undergoes molecular changes and inhibits viral DNA enzymes. This enables the drug to incorporate into the viral DNA itself, thus terminating the chain and preventing it from replicating (Gnann, Barton and Whitley, 1983).

Aciclovir does not destroy the target pathogen but inhibits viral growth and development. Therefore, HSV and VSV will stay latent in the body and can recur (Kinchington et al, 2012).

Uses: to treat viral infections, the most common viral infections a dentist may see are caused by herpes simplex virus (HSV) or varicella-zoster virus (VSV).

Contraindications: risk of hypersensitivity, can interact with ibuprofen. Dosages will need adjusting for children, elderly, pregnant/breastfeeding women and those with renal impairment (consult the GP) (NICE, 2020).

Antiviral prescribing

Viral infections are usually short-lived and diagnosed by their clinical presentation.

Whilst viral infections of the oral cavity are common, caution is necessary in those who are unable to take fluids or are severely immunocompromised, putting them at risk of dehydration. Refer such patients to hospital, along with patients experiencing prolonged non-resolving infections.

  Condition Local measures Prescribing
HSV Primary herpetic gingivostomatitis

 

  • Nutritious diet, fluids, rest, analgesic, antimicrobial mouthwashes.
Benzydamine Oromucosal spray 0.15%

  • Six months – five years: one spray per 4kg body weight (max four sprays) every one ½ hours.
Herpes labialis

 

  • Avoid things that trigger cold sores, sunblock lip balm, fluids, analgesics if painful.

 

Aciclovir cream 5%

  • 2g, apply to lesion every four hours (five times daily) for five days
  • During prodromal stage of lesion.
Infection in immunocompromised patients or those with severe infection
  • Alter diet to include soft foods and enough fluids to avoid dehydration.
Aciclovir Tablets

  • 200mg, send 25 tablets, one tablet to be taken five times daily for five days.
VSV Shingles

 

  • Analgesics, keep rash clean and dry, wear loose-fitting clothing, use cool compress few times daily, contact your GP or call 111 for treatment.
Aciclovir tablets

  • 800mg, five times daily for seven days.

Table 2: Antiviral prescribing following guidance from SDCEP and FGDP

References

Birch M and Sibley G (2017) Antifungal Chemistry Review. In: Comprehensive Medicinal Chemistry III 703-16

Ghannoum MA and Rice LB (1999) Antifungal agents: Mode of action, mechanisms of resistance, and correlation of these mechanisms with bacterial resistance. Clinical Microbiology Reviews 12: 501-17

Gnann JW, Barton NH and Whitley RJ (1983) Acyclovir: Mechanism of Action, Pharmacokinetics, Safety and Clinical Applications. Pharmacother J Hum Pharmacol Drug Ther 3: 275-83

Kinchington PR, Leger AJS, Guedon J-MG and Hendricks R (2012) Herpes simplex virus and varicella zoster virus, the house guests who never leave. Herpesviridae 3: 5

NICE (2020) BNF: British National Formulary. NICE

Catch up with last month’s Student’s guide

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