What Is Muscle Spasticity:
Muscle Spasticity is a condition which affects up to 60% of people with Multiple Sclerosis. It is a condition where a muscle has tone and resists being stretched. When a muscle is stretched a signal is sent to the nervous system which to far the nervous system in turn sends a signal back to the muscle to tell it to contract. In diseases such as MS or Cerebral Palsy the stretch reflexes can become hyper sensitive as signals get crossed and muscles contract involuntarily at times. The muscles which are effected are prone to stiffness and or painful spasms. In people with MS lesions in the nervous system interrupt nerve signals from the brain.This causes problems with mobility as well as muscle weakness.
Current ,Medications,Research ,available treatments for Spasticity
A wide range of medications are currently available to treat Spasticity.
Baclofen,and Diazepam:are currently two of the most commonly prescribed. They reduce muscle spasticity by increasing muscle relaxation.These drugs achieve this muscle relaxation by mimicing gamma-aminobutyric acid which is found in the nervous system and is involved in inhibiting muscle contractions.
  Both of these medications are usually effective but not without the price of some side effects such as drowsiness or toxicity both of which can limit how successfully they can be used.

Tizandine: Is a muscle relaxant and has been approved for the treatment of muscle spasticity which works in a different way than either the Baclofen or Diazepam
Additonal Treatments:
Researchers have been studying some alternative oral medications that may be effective with less severe side effects.
Gabapentin Is one of these such drugs. Originally used to control seizures. In a small study this  reduced spasticity without affecting the patients ability to concentrate nor did it cause fatigue.
Other Treatments: When Oral treatments are ineefective for Muscle Spasticity there are other alternatives. One is to deliver the nedications by a different route. Baclofen has been  infused directly into the fluid space around the spinal cord. This is done by the use of a surgically implanted pump which is refilled using syringes without any further surgery. This method can give significant relief generally with fewer side effects because the medication is going directly into the spinal cord area. This relief does not come without its own price though. Since surgery is required there is always the possibiltiy of infection or a dislocation ot the pump and its tubing following the surgery.
Final Spasticity treatment when medications fail:
A final treatment that can be considered when all else seems to fail is Surgery. The aim of this surgery is to interrupt the spinal reflex causing the spasticity. This is accomplished by cutting the nerves causing the spasticity, the affected muscle or tendon may be cut or the spaticity may be reduced by lengthening the tendon.  While surgery may be effective it must be carefully considered because the changes are most often Irreversible.
Ongoing research:
Currently there have been some recent studies done where Botulinum toxin or BOTOX
has been injected directly into spastic muscles to allow them to relax. This is accomplished because botulinum toxin is a neurotaoxin which blocks the release of the chemical in the body which tells the muscles to relax. Most people are familiar with the use of BOTOX in as a beauty enhancer. It is injected into the face and blocks the cantraction of facial muscles thus eliinating frown lines. In a study of 74 people with MS and spasticity of the hip abductor muscles. The muscles which pull the legs together. Botulin toxin was found to reduce the muscle activity at all doseage levels tried with slightly better results at higher levels. Researchers are still conducting studies to find safe doseage levels as well as the best use of botulinum toxins especially when used in with other treatments.

Why treatment for spasticity can be so hard:
There is no universally recognized  way to measure muscle spasticity. There is no way to compare some test results because different researchers may use different methods of measuring and reporting test results.
Marijuana as a Spasticity treatment:  the human body produces a compounds known as
endocannabinoids which resemble the active chemicals in marijuana. researchers found in tests in laboratory mice that had been induced to form muscle spasticity that the levels of of the endocannabinoids rose. They thought the mice may be making larger amounts of the endocannabinoids to make up for the spasticity. To test this theory they injected the mice with additional endocannabinoids and spasticity was reduced. When researchers did the opposite and injected the mice with drugs to block the production of endocannabioids the spasticity worsened.
This only proves the subjects in this test were mice not humans and alot more research needs to be done.