Can Co-amoxiclav Cause Low Blood Pressure? Understanding the Risks

October 11, 2025 •

4 min read

According to regulatory information, serious adverse reactions to co-amoxiclav, while rare, have been documented. A key concern for patients and healthcare providers alike is whether co-amoxiclav cause low blood pressure, a symptom known as hypotension. Although not a typical side effect, this can occur as part of a severe allergic response or other serious conditions.

Quick Summary

Low blood pressure can be a rare but serious side effect of co-amoxiclav, often occurring due to a severe allergic reaction like Drug-induced enterocolitis syndrome (DIES). It is not a common side effect, and is distinct from interactions seen with other classes of antibiotics and specific blood pressure medications.

Key Points

Allergic Reactions are the Primary Cause: Low blood pressure is primarily a symptom of a severe, rare allergic reaction (anaphylaxis or DIES) to co-amoxiclav, not a common side effect.
DIES Is a Specific Risk: Drug-induced enterocolitis syndrome (DIES), a non-IgE mediated allergic reaction, can cause hypotension and is more commonly reported in children receiving amoxicillin.
Differentiating from Other Antibiotics: Unlike certain macrolide antibiotics (e.g., erythromycin) that can cause hypotension when interacting with blood pressure medications, co-amoxiclav is not typically associated with this risk.
Not a Common Side Effect: The most frequent side effects of co-amoxiclav are gastrointestinal issues like diarrhea and nausea, not low blood pressure.
Immediate Medical Attention is Required: Any signs of severe dizziness, weakness, or unexplained low blood pressure after taking co-amoxiclav warrant immediate medical evaluation.
Gut Microbiota Influence is Under Investigation: Some animal studies suggest amoxicillin might affect blood pressure by altering gut microbiota, but the clinical relevance for humans is not established.

Can Co-amoxiclav Cause Low Blood Pressure? The Link to Allergic Reactions

Co-amoxiclav, a combination of amoxicillin and clavulanic acid (often known by the brand name Augmentin), is a powerful and widely prescribed antibiotic used to combat a range of bacterial infections. For the vast majority of patients, it effectively treats their condition with only mild, common side effects. However, the possibility of serious adverse reactions, such as low blood pressure (hypotension), warrants a closer look.

Rare but Serious Allergic Responses

The primary and most dangerous link between co-amoxiclav and low blood pressure is through severe allergic reactions. These are rare but require immediate medical attention.

Drug-Induced Enterocolitis Syndrome (DIES)

DIES is a specific, non-IgE-mediated allergic reaction to amoxicillin, one of the components of co-amoxiclav, that primarily affects the digestive system and is most common in pediatric patients. Symptoms typically appear 1 to 4 hours after taking the medication and can include:

Severe, repetitive vomiting
Diarrhea
Unusual paleness (pallor)
Lethargy or extreme tiredness
Low blood pressure (hypotension)
In severe cases, shock

If DIES occurs, the drug must be discontinued, and appropriate therapy should be instituted by a healthcare professional.

Anaphylaxis

Anaphylaxis is a severe, rapid, and potentially life-threatening allergic reaction. Although rarer than milder reactions, it is a known risk with penicillin-based drugs like co-amoxiclav. Anaphylaxis can cause a dramatic drop in blood pressure, leading to dizziness, confusion, and even fainting. Other symptoms include difficulty breathing, swelling of the throat or tongue, and hives or a rash.

Is Low Blood Pressure a Common Occurrence?

It is important to emphasize that low blood pressure is not a common or expected side effect of co-amoxiclav. The more typical, and generally less severe, side effects are primarily gastrointestinal. These include:

Diarrhea
Nausea
Vomiting
Indigestion

Other uncommon side effects may include skin rashes and headaches. If a patient experiences dizziness or lightheadedness, which can be symptoms of low blood pressure, it is essential to consider the possibility of a serious allergic reaction and not dismiss it as a typical drug response.

Indirect Mechanisms and Other Potential Factors

Beyond direct allergic responses, other factors may contribute to blood pressure changes in patients taking co-amoxiclav, although these are less directly linked to the medication itself:

Influence on Gut Microbiota: Animal studies, primarily in rats, have shown that exposure to amoxicillin can alter the gut microbiota composition, which has been associated with a reduction in blood pressure. However, the relevance of this finding to humans and its clinical significance remain unclear and require further research.
Interactions with Underlying Infections: For patients already hospitalized with serious infections, studies have found an association between amoxicillin/clavulanic acid prescription and an increased risk of hospitalization for heart failure or shock. This does not necessarily indicate a direct causal effect on blood pressure but rather suggests that underlying infections and the patient's compromised state are significant contributing factors.
Drug Interactions: It is critical to differentiate between antibiotics. While some classes of antibiotics (specifically macrolides like erythromycin) have been linked to dangerously low blood pressure when combined with certain blood pressure medications (calcium-channel blockers), searches indicate no direct interaction leading to hypotension between co-amoxiclav and common antihypertensive drugs. However, always consult a healthcare provider about potential interactions with all your medications.

Comparison of Antibiotic Side Effects and Hypotension


Feature	Co-amoxiclav (Amoxicillin/Clavulanate)	Macrolide Antibiotics (e.g., Erythromycin, Clarithromycin)	Other Antibiotics (Fluoroquinolones)
Mechanism for Hypotension	Rare, serious allergic reactions (Anaphylaxis, DIES)	Drug interaction with Calcium-Channel Blockers (CCBs)	Certain drug-induced cardiac problems
Risk for Hypotension	Very low for the general population; primarily linked to allergic responses	Higher for older patients on specific CCBs when combined with macrolides	Rare, related to specific heart conditions
Prevalence of Common Side Effects	High, especially gastrointestinal issues like diarrhea and nausea	Gastrointestinal upset, but generally lower than co-amoxiclav	Relatively common, including nausea and diarrhea
Cardiovascular Side Effects	Dizziness and lightheadedness can be signs of severe reactions	Can cause irregular heartbeats and low blood pressure via drug interactions	Can cause irregular heartbeat

What to Do if You Suspect Low Blood Pressure

If you are taking co-amoxiclav and experience symptoms of low blood pressure, particularly if they are severe or accompanied by other signs of a serious allergic reaction, you should seek medical help immediately. Key symptoms to watch for include:

Severe dizziness or feeling lightheaded
Confusion or unsteadiness
Extreme weakness or tiredness
Unusually pale skin
Vomiting that occurs within a couple of hours of taking the medication

Conclusion

While co-amoxiclav can cause low blood pressure, it is a rare and potentially serious side effect that is almost exclusively associated with severe allergic reactions, such as anaphylaxis or DIES. It is not a common or typical response to the medication. Most patients experience only mild, temporary side effects like diarrhea or nausea. It is vital for patients and caregivers to be aware of the signs of a serious reaction and to seek immediate medical attention if they appear. If you are concerned about your blood pressure while on this or any other antibiotic, consult with a healthcare professional to discuss your specific risk factors.

For more information on drug side effects, the NHS provides detailed guidance on co-amoxiclav, including how to report side effects: https://www.nhs.uk/medicines/co-amoxiclav/side-effects-of-co-amoxiclav/.

Frequently Asked Questions

The most common side effects of co-amoxiclav include diarrhea, nausea, vomiting, indigestion, and skin rashes. These are typically mild and temporary.

If you experience dizziness, particularly when accompanied by other symptoms like extreme weakness or pale skin, it could be a sign of a serious allergic reaction. You should call your healthcare provider or seek immediate medical help.

Yes, co-amoxiclav, like other penicillin-based drugs, can cause a rare but serious allergic reaction called anaphylaxis. This is a medical emergency that can include a dangerous drop in blood pressure.

No, low blood pressure is not a typical sign of an overdose. It is more commonly associated with severe allergic reactions at therapeutic doses. Overdoses may involve other symptoms, and you should contact emergency services immediately if one is suspected.

Searches for interactions between co-amoxiclav and common blood pressure medications like amlodipine or hydrochlorothiazide generally report no specific interactions causing hypotension. However, certain other antibiotics (macrolides) can cause dangerous interactions with calcium-channel blockers. Always inform your doctor of all medications you are taking.

DIES is a specific type of allergic reaction to amoxicillin that affects the digestive system, primarily in children. Symptoms include severe vomiting, diarrhea, lethargy, and can progress to low blood pressure and shock.

Children, particularly infants, are at a higher risk for Drug-induced enterocolitis syndrome (DIES), which can cause low blood pressure. Otherwise, the side effects in children are often similar to those in adults, with diarrhea being common.