Published: 2 December 2021

Publications

A bitter pill to swallow – medicines that can cause taste disturbances

Published: 2 December 2021
Prescriber Update 42(4): 54–56
December 2021

Medicines have been reported to cause taste disturbances by:^1,2

• altering the perception of taste giving a markedly sweet, sour, salty, bitter, or metallic taste (dysgeusia)
• decreasing taste perception (hypogeusia)
• heightening taste sensitivity (hypergeusia)
• causing a total loss of taste (ageusia).

The mechanisms responsible for taste disturbances are often unknown

Each medicine has unique, often unknown, mechanisms that cause taste disturbances.¹ Some mechanisms may involve the following.

• The direct actions of the medicine through drug-receptor interaction, disturbance of action potential propagation in cell membranes of afferent and efferent neurons, and alteration of neurotransmitter function.³
• Limiting the access of taste substances to sensing receptors (ie, through drying the mucosa, increasing nasal congestion, and closing off taste pores) which can alter the perception of taste.³
• Changing the composition or quantity of saliva. Saliva plays a role as a solvent and transportation medium for taste substances to the taste bud.⁴
• A drug-drug pharmacokinetic interaction resulting in elevated blood-plasma levels of one medicine beyond therapeutic concentrations.¹

There are also significant individual differences in vulnerability to medicine related taste disturbances. Factors likely involved include differences in the dose of the medicine and patient-specific factors, such as genetic polymorphism, age, and other medical conditions.¹

Medicines reported as causing taste disturbances

Table 1 outlines examples of medicines reported to CARM causing taste disturbances.

Table 1: Examples of medicines reported to the Centre for Adverse Reactions Monitoring as causing taste disturbances

Medicine	What the data sheet says
Terbinafine	The Deolate data sheet states taste disturbances, including taste loss has been observed as uncommona in clinical trials or during post-marketing experience. Taste may recover several weeks after discontinuing terbinafine. Remote situations of extended taste disturbances have been observed.
Atorvastatin	The Lorstat data sheet states that in post-marketing experience, dysgeusia has been reported as rare adverse event.
Metoprolol succinate	The Betaloc CR data sheet states taste disturbances is a very rare a adverse reaction.
Omeprazoleb	The Losec data sheet states taste disturbance has been identified in clinical trials and post-marketing setting as rare.a
Varenicline	The Varenicline Pfizer data sheet states dysgeusia has been reported in studies at a rate ≥1% and with an incidence higher than that for placebo.
Zopiclone	The Zopiclone Actavis data sheet states taste alteration (bitter taste) is the most commonly seen adverse reaction in clinical trials.

Notes:

1. Adverse reactions are graded under frequency using the following principle: very common (1/10); common (1/100 to < 1/10); uncommon (1/1,000 to < 1/100); rare (1/10,000 to < 1/1,000); and very rare (< 1/10,000).
2. In 2009, there was an increase in the number of adverse event case reports for omeprazole. While most of the cases were reporting a brand switch, taste disturbances were co-reported for some of them.

Complications and practice considerations

Although a medicine causing taste disturbances may not be considered a life-threatening adverse reaction, it can have a negative impact on patients’ medication adherence, food intake and nutritional status.¹ Patients may compensate for bitter taste or dry mouth by increasing their fluid intake and the resulting increase in urinary frequency can increase the risk of falls or incontinence particularly in the elderly. Increased salt or sugar intake may complicate the management of underlying medical conditions such as diabetes and hypertension.⁵

Healthcare professionals should consider whether poor medication adherence, changes in eating habits or weight loss are attributed to medicine related taste disturbances. Monitoring weight and the early provision of dietary advice can help minimise effects on nutritional status.⁵

There is no standard treatment for medicine related taste disturbances as each medicine will have a unique, often unknown, mechanism causing this disturbance.¹ For most medicines, stopping or changing the dose of the suspected medicine or switching to another medicine are logical approaches to reversing taste disturbance over time.⁶

References

1. Schiffman SS. 2018. Influence of medications on taste and smell. World Journal of Otorhinolaryngology – Head and Neck Surgery 4(1): 84–91. DOI: 10.1016/j.wjorl.2018.02.005 (accessed 23 September 2021).
2. Giudice M. 2006. Taste disturbances linked to drug use: Change in drug therapy may resolve symptoms. Canadian Pharmacists Journal /Revue des Pharmaciens du Canada 139(2): 70–3. DOI: doi.org/10.1177/171516350613900208 (accessed 23 September 2021).
3. Tuccori M, Lapi F, Testi A, et al. 2011. Drug-induced taste and smell alterations: A case/non-case evaluation of an Italian database of spontaneous adverse drug reaction reporting. Drug Safety 34(10): 849–59. DOI: doi.org/10.2165/11593120-000000000-00000 (accessed 23 September 2021).
4. Rademacher WMH, Aziz Y and Hielema A et al. 2020. Oral adverse effects of drugs: Taste disorders. Oral Diseases 26(1): 213–23. DOI: 10.1111/odi.13199 (accessed 23 September 2021).
5. Douglass R and Heckman G. 2010. Drug-related taste disturbance: A contributing factor in geriatric syndromes. Canadian Family Physician 56(11): 1142–7. URL: ncbi.nlm.nih.gov/pmc/articles/PMC2980431/ (accessed 23 September 2021).
6. Doty RL, Shah M and Bromley SM. 2008. Drug-induced taste disorders. Drug Safety 31(3): 199–215. DOI: doi.org/10.2165/00002018-200831030-00002 (accessed 23 September 2021).