Slurred speech, or dysarthria, is a motor speech disorder that makes it difficult to form and pronounce words clearly. It results from impaired control over the muscles used for speech, often due to nervous system effects. While medical conditions can cause dysarthria, certain substances and medications can also lead to this symptom.
How Drugs Affect Speech
Drugs can cause slurred speech by interfering with communication pathways between the brain and speech muscles. Producing speech requires coordinated muscle movements. Substances disrupt these processes by altering neurotransmitter balance or slowing brain activity.
Neurotransmitters transmit signals between neurons. Some drugs enhance inhibitory neurotransmitters like GABA, slowing brain activity. This impairs motor control and balance, affecting clear speech. Other substances might affect dopamine, crucial for motor control. When these systems are disrupted, the brain struggles to send signals to speech muscles, resulting in slurred articulation.
Drug Categories Causing Slurred Speech
Different drug categories cause slurred speech through their effects on the central nervous system. CNS depressants, for example, slow brain function. This reduces coordination and muscle control, impacting clear articulation.
Muscle relaxants also cause slurred speech by relaxing muscles throughout the body, including those essential for speech. This relaxation makes it difficult to control movements of the tongue, lips, and jaw. While less common, certain stimulants can paradoxically affect speech. Though they increase brain activity, some can lead to rapid, disjointed speech or impaired coordination, resulting in slurring.
Common Medications and Substances
Several common medications and substances can cause slurred speech. Alcohol, a CNS depressant, impairs coordination and cognitive function, leading to slurring. It enhances GABA effects, slowing nerve impulses and affecting brain regions that control motor coordination.
Benzodiazepines, used for anxiety, insomnia, and seizures, are CNS depressants that cause slurred speech. Examples include alprazolam (Xanax), diazepam (Valium), and lorazepam (Ativan). Opioids, prescribed for pain, also cause slurred speech due to their CNS depressant effects, impacting muscle coordination. Common opioids include oxycodone, morphine, and fentanyl. Anticonvulsants, used to prevent seizures, can impact speech clarity, such as gabapentin (Neurontin), phenytoin (Dilantin), and divalproex sodium (Depakote). Certain antihistamines, especially older, drowsy types, can lead to slurred speech by affecting the central nervous system and causing dry mouth. Cannabis can also cause slurred speech by slowing mouth muscle movements.
When Slurred Speech Signals Concern
Slurred speech can indicate drug impairment or a more serious underlying issue requiring immediate attention.
If slurred speech appears suddenly, especially with other symptoms, seek prompt medical evaluation.
Concerning symptoms include sudden weakness or numbness on one side of the body, confusion, difficulty understanding speech, or a drooping face. Extreme drowsiness, difficulty breathing, or unresponsiveness with slurred speech also indicate a life-threatening situation. New or unexpected slurred speech should prompt a medical assessment to determine the cause and ensure safety.