Dysgeusia
These include artificial saliva, pilocarpine, zinc supplementation, alterations in drug therapy, and alpha lipoic acid.
[3] Healthy individuals normally have a diverse range of microbial organisms residing in their oral cavities; however, chemotherapy can permit these typically non-pathogenic agents to cause serious infection, which may result in a decrease in saliva.
In a study conducted by Masahide Yasuda and Hitoshi Tomita from Nihon University of Japan, it has been observed that patients with this taste disorder have fewer microvilli than normal.
Based on their findings, dysgeusia results from loss of microvilli and the reduction of Type III intracellular vesicles, all of which could potentially interfere with the gustatory pathway.
Radiation to head and neck also results in direct destruction of taste buds, apart from effects of altered salivary output.
Zinc somehow directly or indirectly interacts with carbonic anhydrase VI, influencing the concentration of gustin, which is linked to the production of taste buds.
[13] Saliva can have traces of the drug, giving rise to a metallic flavor in the mouth; examples include lithium carbonate and tetracyclines.
[15] Drugs that act by blocking the renin–angiotensin–aldosterone system, for example by antagonizing the angiotensin II receptor (as eprosartan does), have been linked to dysgeusia.
[18] Xerostomia, also known as dry mouth syndrome, can precipitate dysgeusia because normal salivary flow and concentration are necessary for taste.
[19] Although it is uncertain what the relationship between bladder relief and dysgeusia entails, it has been observed that the areas responsible for urinary system and taste in the pons and cerebral cortex in the brain are close in proximity.
A wide range of miscellaneous factors may contribute to this taste disorder, such as gastric reflux, lead poisoning, and diabetes mellitus.
[28] The initial history assessment also considers the possibility of accompanying diseases such as diabetes mellitus, hypothyroidism, or cancer.
[28] In order to further classify the extent of dysgeusia and clinically measure the sense of taste, gustatory testing may be performed.
In regional testing, 20 to 50 μL of liquid stimulus is presented to the anterior and posterior tongue using a pipette, soaked filter-paper disks, or cotton swabs.
[27] Threshold tests for sucrose (sweet), citric acid (sour), sodium chloride (salty), and quinine or caffeine (bitter) are frequently performed with natural stimuli.
[30] For example, the Connecticut Chemosensory Clinical Research Center asks patients to rate the intensities of NaCl, sucrose, citric acid and quinine-HCl stimuli, and the loudness of 1000 Hz tones.
Patients usually report sour or metallic sensations similar to those associated with touching both poles of a live battery to the tongue.
For example, the blink reflex may be used to evaluate the integrity of the trigeminal nerve–pontine brainstem–facial nerve pathway, which may play a role in gustatory function.
[39] Xerostomia, or a decrease in saliva flow, can be a side effect of many drugs, which, in turn, can lead to the development of taste disturbances such as dysgeusia.
[44] In a pilot study involving twelve lung cancer patients, chemotherapy drugs were infused with zinc in order to test its potential as a treatment.
[44] Because taste disorders can have detrimental effects on a patient's quality of life, more research needs to be conducted concerning possible treatments such as zinc supplementation.
[48] Due to this drug's inability to treat her condition, she began taking a regimen of eprosartan, an angiotensin II receptor antagonist.
[48] Within three weeks, she began experiencing a metallic taste and a burning sensation in her mouth that ceased when she stopped taking the medication.
[50] It has an important role in the Krebs cycle as a coenzyme leading to the production of antioxidants, intracellular glutathione, and nerve-growth factors.
[51] Because flavors are perceived by differences in electric potential through specific nerves innervating the tongue, idiopathic dysgeusia may be a form of a neuropathy.
[51] ALA has proven to be an effective treatment for burning mouth syndrome, spurring studies in its potential to treat dysgeusia.
An altered sense of taste has effects on food choice and intake, and can lead to weight loss, malnutrition, impaired immunity, and a decline in health.
[47] Patients diagnosed with dysgeusia must use caution when adding sugar and salt to food, and must be sure not to overcompensate for their lack of taste with excess amounts.
In patients undergoing chemotherapy, taste distortions can often be severe, and make compliance with cancer treatment difficult.
For example, the National Institute on Deafness and Other Communication Disorders is looking into the mechanisms underlying the key receptors on taste cells, and applying this knowledge to the future of medications and artificial food products.
