Medication Side Effects - Fact Sheet

Although it is never possible to predict which side effects a person will experience, all prescription drugs have a list of those that are most common. This information can be used to select the most appropriate medications for a patient. Sedation, confusion, dizziness, balance disturbances, blurred vision, and tremors are examples of some fairly common medication side effects that can be particularly detrimental in those with brain injuries. These individuals are often especially sensitive to side effects, so lower-than-normal medication doses are often used.

Newer medications in a given therapeutic class usually cause less side effects than their older counterparts. For example, tricyclic antidepressants (TCAs) cause high rates of side effects such as sedation, dizziness, and anticholinergic effects (dry mouth, confusion, constipation). Even though they are cheap and have proven effectiveness, the TCAs are rarely used in brain-injured patients due to their side effects. Newer antidepressants such as sertraline (Zoloft), citalopram (Celexa), venlafaxine (Effexor XR) and others are preferred because of their better side effect profiles. Likewise, older anticonvulsants such as phenytoin (Dilantin), phenobarbital, and primidone are usually not recommended for use in brain-injured persons due to their extremely poor tolerability profiles compared to newer anticonvulsants.

Sedation is a common effect of many medications. Although usually beneficial at night, it can be problematic when it occurs during the day and interferes with normal activities. Sedation is usually most pronounced when a new medication is started and will sometimes disappear with continued treatment as the person’s body gets used to the drug. This process, known as development of “tolerance”, occurs with many medication side effects. Drugs with strong “anticholinergic” properties can cause confusion and other types of Cognitive impairment, so are best avoided in brain-injured individuals. Examples of these include diphenhydramine (Benadryl), benztropine (Cogentin), TCAs, and many antipsychotic agents.

The primary goal of medication therapy is to achieve beneficial effects with minimal unwanted effects. This goal cannot be achieved if side effects cause distress and/or interfere with functioning. There are a variety of methods for dealing with unwanted drug effects, and in most cases they can be corrected with proper attention. First, it is important that patients taking medication have an understanding of what side effects to expect and which ones might indicate a serious problem. Since tolerance does develop to many side effects, the problem may resolve with continued treatment. The physician may also be able to make a change in the dose or dosing schedule to minimize unwanted effects in certain cases. Sometimes a switch to another medication may be necessary. Patients must be willing to report any unusual or concerning events to their treatment provider in order for them to be addressed. Medication should never be abruptly discontinued without the physician’s knowledge, as potentially serious withdrawal symptoms may result.

Many thanks to The Brain Injury Resource Foundation for permission to adapt this article from their website at www.birf.info.


Copyright Brain Injury Association of Queensland, Inc, Australia, 2007. This is one of a range of fact sheets made available by the Brain Injury Association of Queensland. While all care has been taken to ensure information is accurate, these fact sheets are only intended as a guide and proper medical or professional advice and information should be sought. The Association will not be held responsible for any injuries or damages that arise from following the information provided in these fact sheets. You can visit the Association’s website at www.braininjury.org.au or send emails to This email address is being protected from spam bots, you need Javascript enabled to view it