Adverse Drug Reactions Nurses NEED to Know

Updated June 2026 · Medically reviewed for nurses

10 min read

Adverse drug reactions nurses need to know

Medications are a huge part of modern medicine and how we treat disease — but there are many adverse drug reactions that can occur.

As nurses, it's important to educate our patients about these reactions: what to expect and what to do if they experience them. Some of these are ingrained in us; others are less commonly taught. Make sure you remember to educate the patients being prescribed these medications.

In This Guide

Antibiotic Reactions
1. Antibiotic Diarrhea
2. Allergic Reactions
3. Rifampin & Birth Control
4. Doxycycline & GI Upset
5. Flagyl & Alcohol
6. Fluoroquinolones & Tendons
Non-Antibiotic Reactions
7. Dexamethasone Burning
8. Opioid Reactions
9. Anticoagulants & Bleeding
References

Antibiotics and Adverse Drug Reactions

Antibiotics are essential in treating bacterial disease, but they don't come without their own side effects. There are many different classes, so some reactions apply only to certain antibiotics and some apply to antibiotics as a whole.

1. Diarrhea and Antibiotics

All antibiotics can cause diarrhea, due to normal "good" bacteria in your intestines being killed by the antibiotic, leading to imbalanced digestion. While all antibiotics can cause it, certain ones are more likely to: amoxicillin, cephalosporins, and clindamycin. When mixed with clavulanic acid (i.e. Augmentin), diarrhea tends to be more pronounced.

Watch for C. diff

Clostridium difficile (C. diff) is an opportunistic diarrheal infection that can cause profuse diarrhea and be difficult to treat. Antibiotics increase the risk — especially broad-spectrum agents like cephalosporins, fluoroquinolones, and clindamycin.

Antibiotic-induced diarrhea — Antibiotics disrupt normal gut flora, leading to diarrhea.

Patient education example: "Some watery diarrhea and mild cramping can be expected while on antibiotics. Stay hydrated. If you have excessive diarrhea, severe abdominal pain, abdominal swelling, fever, or blood or pus in your stool, contact your doctor or return to the emergency department."

2. Allergic Reactions

All medications and antibiotics can cause allergic reactions. True allergic reactions cause itchy hives and potentially swelling of the face, eyes, lips, or mouth. They can even cause swelling of the airways, leading to wheezing and stridor. When giving any prescribed medication, the patient should always be educated on the potential signs.

Allergic reaction signs — Hives and facial/airway swelling are red flags for an allergic reaction.

Patient education example: "All new medications can cause allergic reactions. If you develop a red, raised, itchy rash, immediately stop taking the antibiotic and call your doctor. If you develop swelling of the face, eyes, lips, tongue, or shortness of breath, this is potentially a life-threatening reaction called anaphylaxis — seek immediate medical care or call 911."

3. Rifampin and Birth Control

Antibiotics were frequently thought to interact with birth control, but this is somewhat of a myth. There is no convincing evidence that any antibiotic other than rifampin interacts with birth control. Rifampin is not commonly prescribed but is the recommended treatment for tuberculosis.

There is a concern that antibiotics as a whole can affect the gut microbiome and alter estrogen levels, but this has not been proven and is likely untrue. If patients are prescribed rifampin, educate them to use backup protection for up to 1 month after they finish it.

Patient education example: "While commonly believed to interact with birth control, there's no evidence that most antibiotics do. To be safe, you can use a backup method like condoms while taking the antibiotic and for up to a few days to a month after you finish."

4. Doxycycline and GI Upset

Doxycycline is commonly given for cellulitis, URIs, tick-borne illnesses, pneumonia, STDs, and more. It works great but has some significant adverse drug reactions. It can cause significant GI upset — nausea, vomiting, and diarrhea. Taking it with food or milk can help, although it may inhibit some drug absorption.

Pill Esophagitis

Doxycycline (and clindamycin) can cause drug-induced esophagitis, leading to significant inflammation and pain in the esophagus. To prevent this, educate the patient to take doxycycline with a full glass of water, milk, or food, and to stay upright for 30 minutes afterward.

Patient education example: "Doxycycline can cause significant nausea and vomiting; milk or food directly after taking it can help. Drink it with a full glass of water and remain upright for 30 minutes afterward to prevent damage to your esophagus."

5. Flagyl and Alcohol

Metronidazole (Flagyl) is commonly given for intestinal infections like colitis or diverticulitis, and for vaginal infections like trichomoniasis. It is traditionally taught to NEVER be taken with alcohol, as this can cause a "disulfiram-like reaction" — excessive nausea, vomiting, and other unpleasant symptoms.

Evidence of this severe reaction occurring with Flagyl is somewhat lacking, but it can sometimes occur. Educate the patient on the potential reaction; if they do drink, they may be fine. It's never a bad idea to recommend against taking medications with alcohol.

Patient education example: "Flagyl can potentially cause nausea and vomiting if taken with alcohol. Avoid any alcohol consumption while taking it."

6. Fluoroquinolones and Tendon Rupture

Fluoroquinolones are a powerful broad-spectrum antibiotic class, commonly used to treat UTIs, abdominal infections, and pneumonia. They've fallen out of favor recently due to their large number of potential side effects, even if rare.

Hyper/hypoglycemia

Peripheral neuropathy

CNS effects — seizures, increased ICP, tremors

Psychiatric reactions — psychosis, hallucinations, delirium

Aortic aneurysm and dissection

Tendonitis and tendon rupture

Tendon rupture from fluoroquinolones — Tendinopathy (often the Achilles) can occur hours to months after starting therapy.

The tendinopathy can occur hours or days after starting, or be delayed for months. It's more likely in those > 60 years old, on steroids, with diabetes or kidney failure, or on extended therapy.

Patient education example: "Cipro can rarely cause significant side effects like inflammation and even rupture of your tendons, most commonly the Achilles tendon above your heel. If you feel any swelling or pain in this area or near another joint, immediately stop taking it and contact your doctor."

Non-Antibiotics and Adverse Drug Reactions

Antibiotics aren't the only cause of adverse drug reactions — every medication has expected side effects. Here are a few common or interesting ones you should know to educate your patients about.

7. Dexamethasone and the "Burning Crusade"

Dexamethasone is a steroid given for sore throats, cerebral edema, migraines, and various conditions in and out of the hospital. It's commonly ordered IV, and one interesting side effect you need to warn patients about is perineal discomfort when given IV. When pushed rapidly, perineal burning or tingling can occur — I've personally heard "MY CROTCH IS ON FIRE!"

Slow It Down

The discomfort is usually short-lived but can be shocking for the patient if not warned. Dilute the dexamethasone in NS and infuse over 15–30 minutes to help minimize this side effect.

Patient education example: "I'm going to give you some IV dexamethasone. Sometimes it can cause brief burning or discomfort in your groin, but we're giving it slowly to try to prevent that. It can still happen, so I just want you to be aware."

8. Adverse Drug Reactions with Opioids

Opioids like oxycodone or hydrocodone are commonly given for pain and can be a great tool. Unfortunately, they have significant side effects that need to be taught. Opioids cause respiratory depression — this is how opioid overdoses kill. At appropriate doses, significant respiratory depression shouldn't occur unless mixed with other medications or alcohol. Opioids also cause drowsiness and even stupor, so anything requiring high mental alertness — like driving or operating heavy machinery — needs to be avoided.

Patient education example: "Oxycodone helps your pain but can cause drowsiness, so you shouldn't drive or operate heavy machinery. It can increase your risk of falls, so be careful on stairs. Never take this medication with alcohol, other opiates, or benzodiazepines like Xanax or Ativan."

9. Anticoagulants and Bleeding

Anticoagulants are often necessary to prevent blood clots in those with a history of DVT, PE, or atrial fibrillation. Unfortunately, they also hinder the body's natural ability to clot when injured, leading to ineffective clotting and an increased risk of bleeding. Patients on blood thinners should take extra precautions to prevent trauma like falls.

Head Injuries Need Imaging

If there is a head injury, these patients should be evaluated by a medical professional — preferably in the ED, where a CT scan can be obtained to rule out an intracranial bleed.

Patient education example: "Eliquis helps prevent blood clots, but it also increases your chance of bleeding. If you fall or sustain any injury, be evaluated by a doctor. If you hit your head, call your doctor or come to the ER."

Clinical Pearls

Patient education is part of the dose. Telling a patient what to expect — and what's a red flag — is how reactions get caught early.

Rifampin is the real OCP interaction. Most antibiotics don't reduce birth control efficacy — rifampin is the exception.

Upright + water for doxycycline. Prevents pill esophagitis, a painful and avoidable reaction.

Anticoagulant + head injury = imaging. Low threshold for CT to rule out an intracranial bleed.

References

Antibiotic Diarrhea & C. diff

Rifampin & Birth Control

Doxycycline / Pill Esophagitis

Flagyl, Fluoroquinolones, Dexamethasone & Opioids

4.9 8 votes

Article Rating

What do you want to learn today?

Adverse Drug Reactions Nurses NEED to Know

Antibiotics and Adverse Drug Reactions