Medication side effects, adverse effects and allergies
There are several types of unintended effects that can happen after taking a medication. The main categories are side effects, adverse effects (or adverse reactions), and drug allergies. In everyday conversation, side effect and adverse effect are often used interchangeably, but they’re not exactly the same.
Common side effects and adverse effects of drugs
| Drug | Side effect or adverse effect |
|---|---|
| Insulin | Hypoglycemia |
| Anticoagulants (e.g. warfarin) | Bleeding |
| Antibiotics | Diarrhea |
| Opioid analgesics | Respiratory depression, addiction |
| Digoxin | Upset stomach, vomiting, vision changes |
| Phenytoin | Confusion, lack of coordination |
| Carbamazepine | Dizziness, drowsiness |
| Metformin | Lactic acidosis |
| Antidepressants | Weight gain |
| Chemotherapy | Hair loss, anemia |
Drug allergies most often show up as skin symptoms, such as rashes, itching, and hives. Some people also develop wheezing, swelling, or fever. Less common signs include joint swelling, a high eosinophil count, anemia, and blood in the urine.
In some cases, a drug allergy can be severe and lead to anaphylaxis. Anaphylaxis may include trouble breathing, severe hypotension, weak pulses, seizures, and swelling of the airway.
Most drug reactions are mild to moderate. Severe reactions are rare but can include liver failure, renal failure, cardiac arrhythmias, immunosuppression, severe skin rashes, and birth defects.