Effects of aging on the human taste system.

Losses in taste perception as well as distortions of gustatory function occur with greater frequency in older individuals, and these changes are exacerbated by certain medical conditions, pharmacologic interventions, radiation, and exposure to toxic chemicals. Medications, especially drug-drug interactions, are the most significant yet underappreciated contributors to taste disorders in the elderly. Taste disorders frequently occur when the fraction of an orally administered drug dose that reaches the systemic circulation is markedly increased due to inhibition (by a coadministered drug) of the efflux transporter P-glycoprotein and/or inhibition of the cytochrome P450 metabolism system, which normally limit systemic availability of drugs. The supratherapeutic plasma drug concentrations that result from drug-drug interactions can induce a taste from the blood side of taste cells (intravascular taste), alter taste cell biochemistry, and/or modify other aspects of the taste pathways.