D-Amphetamine for enhancing stroke recovery?
D-Amphetamine for enhancing stroke recovery?
Dextroamphetamine, or D-amphetamine, is classified as a psychostimulant drug that promotes increased alertness and focus, as well as decreased fatigue. It is commonly used in the treatment of narcolepsy and ADHD (it is the primary component of the medicine Adderall). It’s effects on the cardiovascular system (potential problems with increased blood pressure and heart rate) are a concern when considering it’s use after a stroke.
Several studies have shown d-ampheatmine to enhance neuronal sprouting and stroke recovery in rats and monkeys: (Stroke , Neurorehabilitaition and Neural Repair, Neuroscience Letter ).
HOWEVER, the mechanisms are not well understood, and the studies on human populations haven’t been so promising.
Cochrane Database Review in 2007 identified 10 small randomized trials of amphetamines in patients with stroke. They concluded that there is not enough evidence to support the routine use of amphetamines to promote recovery after stroke. Further controlled trials are needed.
Clinical Rehabilitation published a small study in 2003 that failed to show any effect of D-amphetamine on stroke recovery compared with the control group.
In 2001, Cerebrovascualar Disease published a study that compared traditional rehab to rehab combined with administration of d-amphetamine. They found that ”all patients improved significantly over the intervention period. Amphetamine-treated patients did not show any increase in motor function or ADL as compared to the control group.”
Restorative Neurology and Neuroscience published a study in 2005 on the effects of d-amphetamine on arm recovery. They concluded that “d-Amphetamine failed to facilitate motor performance during training sessions, to promote skill acquisition with training tasks, and most importantly to enhance motor recovery among patients with mild arm paresis after stroke.”
Cerebrovascular Disease in 2003 published a study concluding that “an increased intensity of physiotherapy in combination with dexamphetamine during the first week after stroke onset did not affect short- or long-term outcome in this limited sample of patients with severe stroke.” This study lasted only 5 days, and involved subjects with severe weakness and impaired consciousness no greater than 5 days after a stroke.
Stroke published a study in 2006 which concluded that “in stroke patients with a severe motor deficit, 10 mg AMPH coupled with physiotherapy twice per week for 5 weeks in the early poststroke period provided no additional benefit in motor or functional recovery compared with physiotherapy alone.”
So why do studies on rats show that it works, while studies on humans generally don’t?
Here’s a really in-depth article on the potential reasons that the results of animal studies on d-amphetamines haven’t been found in human studies. Published in Neurorehabilitation in 2009.
There IS some research showing that d-amphetamine could enhance speech recovery after a stroke:
International Journal of Neuropsychopharmacology in 2007 published a study which found that, “compared to placebo, Dex enhanced both the rate of learning and the retention of words 1 wk and 1 month later.” They concluded that d-amphetamine seemed to promote improved short-term memory related to speech.
Neuropsychopharmacology in 2004, published a study that attempted to determine if the beneficial effects that some studies have found in D-amphetamine’s use to improve language re-learning after stroke are related to the drug’s arousing action on the cardiovascular system (increased heart rate, blood pressure, etc), or due to other mechanism’s of true neuroplasticity enhancement. They concluded “that AMPH’s plasticity-enhancing effect in humans is not related to its cardiovascular arousal. This suggests that the beneficial effects in stroke patients could also be obtained by less cardiovascular active drugs. Most stroke patients are excluded from treatment with this drug because of a significant risk of cardiovascular dysregulation.”