Treatments for nausea and vomiting can include some oral medications, rectal suppositories, and IV combinations. Through compounding new routes of administration or combinations can be made, including transdermal and intranasal routes.
https://www.ncbi.nlm.nih.gov/pubmed?term=8625179 

Intranasal metoclopramide.
https://www.ncbi.nlm.nih.gov/pubmed?term=10473023 

Nasal absorption of ondansetron in rats: an alternative route of drug delivery.
https://www.ncbi.nlm.nih.gov/pubmed?term=10803929

Bioavailability of Promethazine in a Topical Pluronic Lecithin Organogel: A Pilot Study
https://www.ijpc.com/abstracts/abstract.cfm?ABS=2203

Problems like dry mouth, stomatitis, and mucositis are common in cancer patients and other populations. By treating these ailments at the site of the problem with compounded mouthwashes, solutions, lozenges, and topical products the patient is able to receive relief without as many side effects of other therapies. Use of orally administered anhydrous crystalline maltose for relief of dry mouth.
https://www.ncbi.nlm.nih.gov/pubmed?term=11246934 

Oral glutamine reduces the duration and severity of stomatitis after cytotoxic cancer chemotherapy.
https://www.ncbi.nlm.nih.gov/pubmed?term=9762946

Allopurinol mouthwashes in the treatment of 5-fluorouracil-induced stomatitis.
https://www.ncbi.nlm.nih.gov/pubmed?term=8192112

Topical Morphine for Oral Mucositis in Children: Dose Finding and Absorption.
https://www.ncbi.nlm.nih.gov/pubmed?term=22658469 

These mouth diseases can be both painful and cause serious side effects of not treated. Hygiene and dentist treatments are currently the main treatments, but research is showing adjunct pharmacological therapy along with the current regimens will increase patient response. A comparative evaluation of atrigel delivery system (10% doxycycline hyclate) Atridox with scaling and root planing and combination therapy in treatment of periodontitis: A clinical study.
https://www.ncbi.nlm.nih.gov/pubmed?term=22628962

Folate mouthwash: effects on established gingivitis in periodontal patients.
https://www.ncbi.nlm.nih.gov/pubmed?term=6386897

Antiseptic mouthwashes are commonly used to prevent and treat oral infections, but they can come with undesirable side effects like discoloration of teeth or alternations in taste perceptions. Using some compounded mouthwashes these side effects may be avoided while still obtaining similar anti-infective results.

The use of Betadine antiseptic in the treatment of oral surgical, parodontological and oral mucosal diseases.
https://www.ncbi.nlm.nih.gov/pubmed?term=10462910