Results of Clenbuterol Study Are Mixed

According to the results of a pilot study conducted by researchers working in Italy, the possible effects of the drug clenbuterol were mixed.
 
Clenbuterol is a drug that researcher hope may be able to be used by doctors to treat patients who are suffering from spinal-buler muscular atrophy, a disorder more commonly called SBMA or Kennedy syndrome.
 
  • The study concluded that the drug appeared to be well-tolerated by the 20 patients who received it during the trial. However, the researchers said that some safety issues did appear during the course of the study.

Clenbuterol is a type of drug known as a beta 2 antagonist, a member of a class of drugs that are known to increase a patient’s heart rate and promote effective nervous system function. The researchers believe that clenbuterol may be able to act as an anabolic, allowing it to promote muscle growth.

They do not, however, believe that they have isolated what the underlying mechanism might be that causes the potential muscle-building effect.

  • The drug is approved in some parts of the world as a treatment for asthma, but it is not currently approved by the U.S. Food and Drug Administration to treat any conditions that might be present in humans.

The researchers conducting the study said that they wish to continue with mouse model work in order to try to determine what the mechanism involved could be. They also have told authorities that they believe that further clinical studies should be conducted using either clenbuterol or another member of the beta 2 antagonist class of drugs.

The study was published in the May 3, 2013 edition of Neurology.

How the Study Was Conducted

The researchers worked with 20 individuals who were determined by genetic testing to have SBMA. The participants in the study were able to walk either independently or with the assistance of a cane. The researchers worked up a detailed medical history regarding each patient, and they did a full evaluation of the participants’ cardiac functions in order to establish a baseline for the tests.

  • Each person in the study was given a single dose of clenbuterol, consisting of one 0.02 milligram tablet, each day for two days. The researchers then raised the dosage to two pills per day for the remainder of the 12-month study.

A number of tests were conducted in order to determine the safety of the drugs and to establish how much muscle and respiratory function might have improved. Participants were asked to take part in a six-minute walk test in order to establish their physical ability.

They also took a forced vital capacity test, a test that measures how much air a person can exhale within the span of a minute.

Researchers also assessed each participant, assigning a Medical Research Council muscle score, measuring the strength of individual muscles. The study assigned participants a score according to the Revised ALS Functional Rating Scale (ALSFRS-R), a widely accepted method used to judge functional abilities in people suffering from ALS, a neuromuscular disorder.

These tests were administered by the researchers during follow-up visits that occurred at the three-, six-, 9-, and 12-month points in the study. Clinical tests were also conducted to check the participants’ hearts rates and also to look for signs of any possible heart-related side effects from the drug.

 

Concerns About and Benefits of Clenbuterol

Of the 20 individuals who participated in the study, 16 were able to complete it. Two of the participants left at the three-month mark due to hand tremors, one had to undergo an unrelated surgical procedure and one was asked to leave due to failure to comply with procedures.

Overall, the study determined that clenbuterol is well-tolerated by patients. Nine of the participants, however, reported hand tremors, and three others experienced muscle cramps. These side effects appeared early during the course of the treatment, and they declined as the participants continued.

  • The researchers said that tests of blood levels of the creatine kinase enzyme rose by an average of 46 percent among the participants.

  • Creatine kinase is known to leave damaged muscle fibers, and it is considered a possible sign of muscle injury.

The study showed that participants were able to improve the distance that they could travel in the six-minute walk test by an average of 12.7-percent within three months, and the result was sustained after 12 months had passed.

SBMA patients typically experience an 11-percent decrease per year in average distance traveled in the six-minute walk test.

The forced vital capacity of participants also improved 19.4-percent within the first three months, and this improvement was also sustained over 12 months.

The results of the MRC and ALSFRS-R tests conducted during the baseline and follow-up exams reflected no difference in muscle strength, despite the improvements shown in other tests.

 

Call for Additional Studies of Clenbuterol

The study’s authors said that they would like to see continued research into the effects of clenbuterol, and they suggested further animal model testing ought to be conducted.

They also noted that they believed that further clinical studies should be conducted to determine if the drug may have therapeutic benefits.

MDA Vice President of Research Jane Larkindale said, “The positive result of this small pilot study is encouraging for the development of a treatment for SBMA.” She added, “However, researchers will need to look carefully at this data to design new studies to determine why increased creatine kinase was observed, as long-term muscle damage may prevent this compound’s use. Other related compounds also should be considered for testing.”

Source: http://quest.mda.org/news/sbma-mixed-results-study-clenbuterol