Menthol-nicotine combo may be harmful to lungs: study

Menthol acts in combination with nicotine to desensitise receptors in lungs' airways that are responsible for nicotine's irritation, a new study has found.
"We know that a menthol cough drop soothes a scratchy, sore throat. The question we looked at is if and how it works when the irritant is nicotine," said study author, Kenneth Kellar, a professor of pharmacology at the Georgetown University Medical Centre (GUMC).
"This study supports the notion that menthol is not just a flavouring, but has a pharmacologic effect," Kellar said.
The US Food and Drug Administration (FDA) is considering restrictions on menthol cigarettes because it has determined that menthol in cigarettes is likely associated with increased initiation and progression to regular cigarette smoking, increased dependence, and reduced success in smoking cessation, researchers said.

The study provides a better understanding of how menthol affects the function of one of the most prevalent nicotinic acetylcholine receptors expressed in the peripheral nervous system, they said.
These receptors are expressed in airway sensory nerves as well as other neurons.

"These receptors are also found in the brain, but we don't know yet what effect menthol has on those receptors, or whether they contribute, in any way, to nicotine addiction," Kellar said.
"The issue may be that menthol in the presence of nicotine may reduce the irritation enough that a smoker can inhale more deeply, bringing not just nicotine but toxic smoke products farther into the lungs," said co-investigator Gerald Ahern, an associate professor of pharmacology at GUMC.

"It is possible that such deeper inhalation of menthol cigarettes, to the extent it occurs, increases the already substantial health harms from smoking," said Ahern.