More bad news for smokers

by James J. Galligan, Ph.D., Associate Chair,
Department of Pharmacology and Toxicology

Chantix (Varenicline) is one of the most popular smoking cessation drugs available by prescription.  However, a number of problems with this drug have been identified and this has led to many restrictions on its use.  These problems include an increased incidence of depression, suicidal thoughts, lightheadedness and fainting.

Results of a recent study published in the Canadian Medical Association Journal add another potential problem for Chantix.  These investigators conducted a meta-analysis of 14 published papers describing the beneficial and negative effects associated with Chantix when used to treat nicotine addiction.  The investigators included only double-blind randomized controlled trials in their analysis.  This means that subjects and investigators did not know who was receiving Chantix vs. placebo (simply a sugar pill with no active ingredients) and subjects were assigned to the Chantix or placebo group randomly.  This reduces the chance that subjects at risk for cardiovascular problems were assigned more frequently to the Chantix group.  The investigators analyzed data from 8,216 subjects.  Their study revealed a small but statistically significant increase in the risk for cardiovascular problems such as heart attacks or strokes in the subjects taking Chantix.  Although there was a difference, it was small.  In the Chantix group 52 of 4908 (1.06%) subjects experiences a so called adverse cardiovascular event while in the placebo group 27 of 3308 (0.82%) subjects experienced the same kind of event.

There are some points worth discussion here.  Firstly, it is not surprising that Chantix might be associated with cardiovascular complications.  Chantix is a nicotine replacement therapy.  Therefore, Chantix shares many of the same pharmacological actions of nicotine.  Cigarette smoking does increase the risk of cardiovascular disease partly because cigarette smoke contains nicotine (cigarette smoke also contains carbon monoxide and other toxins which are not present with Chantix).  Nicotine increases blood pressure and increase blood clots which can cause heart attacks and strokes and Chantix may do this as well.  Secondly, although the increased risk for adverse events in the Chantix group was small, the overall sample size was also small (<5,000 subjects).  Worldwide, there are millions of people using Chantix to help kick the smoking habit and therefor a much larger number of patients might be at risk worldwide.

Finally, it is important to remember that all drugs cause side effects (some worse than others).  When deciding whether or not a drug should be used, the doctor and patient must consider the risk vs. the benefit.  Chantix might produce a small increase in the risk for a heart attack or stroke in a patient trying to kick the nicotine habit.  But, what is the heart attack/stroke risk for that patient if he/she continues to smoke?  Many smokers become former smokers without the need for drugs like Chantix but there are also many smokers who have quit hundreds of times.  This is the subset of people who are most likely to benefit from nicotine replacement treatments.  Larger studies will likely reveal the real risk/benefit ratio of Chantix when used to treat nicotine addiction.

In the meantime, the wise person will discuss these issues with their doctor before using Chantix to help kick the smoking habit.

 

Additional information available can be found at:

• Nature News Blog
• CNN
• “Pfizer questions findings of new report on smoking-cessation treatment Chantix” – mlive.com

 

What’s up with potassium iodine?

by James J. Galligan, Ph.D., Associate Chair,
Department of Pharmacology and Toxicology

The recent earthquake and tsunami in Japan has caused severe destruction and has damaged a nuclear power plant.  This poses the danger of release of radioactive materials into the atmosphere and subsequent exposure to the people living near the damaged plant.  You may have heard on the continuous news coverage of this catastrophe that medical personnel are providing potassium iodine to people at risk for radiation exposure.

Why is potassium iodine useful for protection against radiation toxicity?  To answer this question we first need to discuss the thyroid gland.  The thyroid gland produces thyroid hormone which is released into the circulation to regulate metabolism of cells throughout the body.  Cellular metabolism generates body heat and energy utilization.  Thyroid hormone contains iodide and without iodide there is not thyroid hormone and this disrupts normal cell metabolism.  Normally iodine comes from dietary sources (including iodized salt) and this is sufficient to maintain normal thyroid function.  One of the toxic substances released from a damaged nuclear reactor is radioactive iodine.  When people breathe in radioactive iodine contaminated air, they are giving themselves a dose of this toxic substance.  Radioactive iodine accumulates in high concentrations in the thyroid gland and the radiation can then damage the thyroid or cause thyroid cancer. 

Interestingly, radioactive iodine is used to treat thyroid cancer as the radiation will kill off the tumor cells and iodine accumulates in the thyroid gland.  Anyway, people who are at risk will be protected against accumulation of radioactive iodine in the thyroid gland by potassium iodine supplements.  Potassium iodine fills up the thyroid stores of iodine leaving no room for radioactive iodine to accumulate.  Because potassium iodine is safe and non-toxic, there is no risk to using this preventative treatment.

Let’s hope that there is a quick and uneventful resolution to the current nuclear danger in Japan.  In the meantime, supplements of potassium iodine will help reduce the long term risks of exposure to any leaking radiation.