Learn More about Our Genetic Test to Find Your Risks for Side Effects
Almost 79 million Americans use some form of psychotropic drug. Psychiatric medications include antidepressants, antipsychotics, anti-anxiety drugs, mood stabilizers and stimulants used to treat mental health conditions such as anxiety, depression, attention deficit disorder and schizophrenia. Some are used for non-psychological ailments including pain and neuropathy.
Common Side Effects of Psychiatric Medications
Most psychiatric drugs have side effects, although not every patient experiences adverse effects. Common side effects include blurred vision, headaches, nausea and drowsiness. A small percentage of patients experience severe or life-threatening adverse reactions such as fever, seizures or difficulty breathing. These drugs must be used under the supervision of a clinician. Patients must strictly adhere to prescription protocols to avoid side effects, drug interactions or withdrawal symptoms.
Adverse reactions to psychiatric drugs occur for a number of reasons including diet, type and severity of disease and use of other medications. Some reactions occur because of a person’s unique genetic makeup. Studies demonstrate that particular genes affect the metabolism of specific medicines. Pharmacogenetics looks at the way an individual metabolizes and responds to drugs. Knowing a patient’s genetic characteristics allows clinicians to select medications that have the greatest therapeutic value and minimize adverse drug events.
Antidepressants Side Effects
Antidepressants are used to treat several conditions including depression, anxiety, pain, smoking cessation, neuropathic pain and sleep disorders. These drugs correct chemical imbalances in the brain. Neurotransmitters, chemicals produced by nerve cells in the brain that communicate with one another, include dopamine, gamma-aminobutyric acid, norepinephrine and serotonin. Antidepressants inhibit chemical imbalances and enhance communication between cells.
Older antidepressants include monoamine oxidase inhibitors such as selegiline, tetracyclics such as mirtazapine and tricyclics such as amitriptyline. MAOIs may produce side effects such as muscle cramps, low blood pressure and weight gain. MAOIs also interact with certain foods, so dietary restrictions are necessary. Common side effects of tricyclics and tetracyclics include constipation, dizziness and dry mouth. More serious side effects include thoughts of suicide, vomiting and hives.
Newer antidepressants include serotonin reuptake inhibitors such as fluoxetine and sertraline, and serotonin and norepinephrine reuptake inhibitors such as duloxetine and bupropion. These drugs are more commonly prescribed because they produce fewer adverse reactions. Side effects of SSRIs and SNRIs include agitation, sweating and abnormal thinking. These drugs should not be combined with other medicines or herbs that increase serotonin levels in the brain such as older antidepressants, St. John’s Wort or amphetamines. Drug interactions may cause a life-threatening condition called serotonin syndrome or gastric bleeding.
Clinicians typically prescribe antidepressants by trial and error to determine whether a patient will suffer adverse reactions and find a dosage that controls symptoms while minimizing side effects. When patients suffer side effects or do not get relief, the doctor may change medicines. Antidepressants should be stopped only under the guidance of a healthcare professional to avoid relapse or serious side effects.
Anti-Anxiety Drugs Side Effects
Anti-anxiety medicines are used to treat anxiety disorders such as panic attacks, phobias and excessive worry. Most medicines in this category are benzodiazepines such as clonazepam, chlordiazepoxide and diazepam. Beta-blockers such as propranolol and antihistamines such as hydroxyzine are also used to treat anxiety. Like depression, anxiety disorders often occur because of chemical imbalances in the brain. Although these medicines cannot cure the disorders, they can provide relief from symptoms. Benzodiazepines target GABA transmitters, while antihistamines provide a sedative effect. Beta-blockers ease anxiety such as stage fright or post-traumatic stress. Anticonvulsants such as gabapentin and topiramate are often used to augment therapy.
Each of these medications may produce minor side effects such as dizziness, fatigue or drowsiness. Benzodiazepines are usually used on a short-term basis because they can be habit-forming. They should not be stopped abruptly because of the risk of side effects and seizures or be combined with alcohol or other central nervous system depressants. Beta-blockers should not be used by people with asthma or diabetes. Some anticonvulsants like topiramate are associated with visual changes and decreased sweating. Anticonvulsants should be stopped gradually to avoid the risk of seizure. Combining anti-anxiety drugs with other medications should be done only under the guidance of a physician to avoid serious side effects from drug interactions.
Side Effects of Antipsychotics
Antipsychotics are used to manage mental disorders including psychosis, schizophrenia, delirium and dementia. Antipsychotics block dopamine receptors. Older medicines, called “typical” antipsychotics or neuroleptics, include chloropromazine and haloperidol. Newer drugs, called “atypical” antipsychotics, act on both dopamine and serotonin receptors. Atypical antipsychotics include risperidone and lurasidone. Common side effects of atypical
antipsychotics include tremors, seizures, constipation and restlessness. Typical antipsychotics may also impair movement or cause rigidity or muscle spasms. Long-term use may cause tardive dyskinesia, or uncontrollable movements around the mouth. Antipsychotics should not be stopped abruptly to avoid withdrawal symptoms.
Stimulants Side Effects
Stimulants increase heart rate, attention and blood pressure. They are used to treat attention deficit hyperactivity disorder, depression and other health conditions. Medicines used to treat ADHD include dextroamphetamine and methylphenidate. Common side effects include sleeplessness and loss of appetite.
Mood Stabilizer Side Effects
Mood stabilizers are used to treat mood swings and bipolar disorder. They may also be used with other psychiatric drugs to treat other mental health problems. Lithium is commonly used for these disorders. Anticonvulsants such as carbamazepine and valproic acid are also used. Side effects include itching, blackouts, seizures or loss of coordination.
Pharmacogenetic Testing and Adverse Drug Reactions
Pharmacogenetic testing examines a patient’s DNA to identify gene variants that can affect the metabolism of drugs. The cytochrome P450 family of genes metabolizes most psychiatric drugs. Genetic variations can affect the rate of metabolism. Slow metabolism may result in adverse side effects. Rapid metabolism may eliminate a drug too quickly and reduce the therapeutic value.
Some genes affect the metabolism of antipsychotic medicines that bind with dopamine. Other genes affect how SSRIs are assimilated. Some variants are common to particular ethnic groups; others are individual. Studies show that particular genotypes had a 50 percent higher risk of developing tardive dyskinesia. Another genetic variant is associated with a reduced risk of TD, suggesting the gene may protect from developing TD. Drugs such as clozapine that bind with serotonin receptors are associated with lower incidences of TD.
Gene CYP2D6 metabolizes several antidepressants and approximately 40 percent of antipsychotics including risperidone and haloperidol. Poor metabolizers of CYP2D6 are more likely to suffer side effects from several commonly prescribed antipsychotics. Genotyping for CYP2D6 can help predict metabolic responses for several antidepressants and neuroleptics. The Food and Drug Administration has issued drug label warnings and dosing recommendations for specific genetic variants for several psychiatric drugs including clozapine, risperidone and amitriptyline.
Clinicians and pharmacists trained in pharmacogenetics can help patients understand the potential for adverse effects of psychiatric drugs that may be due to genetic variants. When testing results are included in a patient’s medical records, pharmacists can verify that medications are appropriately dosed and communicate information about how to use the drug to patients. Reducing side effects makes patients more confident about the medications prescribed by their doctors, which can increase patient adherence to drug therapy regimens.