A persistent cough is an irritating symptom often attributed to allergies, infections, or environmental irritants. However, a significant number of chronic cough cases are directly linked to medications prescribed for unrelated health conditions, such as those used for high blood pressure or heart disease. This phenomenon, known as a drug-induced cough, is a side effect that can develop in patients receiving long-term treatment. Recognizing that a prescribed drug can trigger this reaction is the first step in addressing the discomfort and understanding the biological mechanisms behind this often-overlooked adverse effect.
Medications Most Likely to Induce Cough
The most frequent cause of a medication-related cough stems from Angiotensin-Converting Enzyme (ACE) Inhibitors, commonly prescribed for hypertension and heart failure. These medications, including lisinopril, enalapril, and ramipril, are potent treatments but can cause a persistent dry cough in an estimated 5% to 35% of patients. This reaction is considered a “class effect,” meaning it is a potential side effect of nearly all drugs within this group.
While ACE inhibitors are the primary offenders, other medication classes have also been implicated. Certain beta-blockers, used to treat high blood pressure and heart problems, may induce coughing, particularly in patients with pre-existing respiratory conditions like asthma.
Some inhaled medications, such as dry powder inhalers or certain steroid nasal sprays, can cause a cough through direct mechanical irritation of the throat and airways. This irritation is localized and physical. Additionally, a small number of patients taking calcium channel blockers may experience a cough indirectly due to the medication worsening gastroesophageal reflux disease (GERD), which allows stomach acid to irritate the throat.
The Biological Basis of Medication-Related Cough
The mechanism by which ACE inhibitors induce a cough centers on their effect on bradykinin, a natural compound. ACE inhibitors block the angiotensin-converting enzyme to prevent the conversion of angiotensin I to angiotensin II, which lowers blood pressure. However, the angiotensin-converting enzyme is also responsible for the breakdown and inactivation of bradykinin and a neurochemical called substance P.
When the enzyme is blocked, bradykinin and substance P accumulate in the respiratory tract. This buildup increases the sensitivity of cough receptors in the airways, leading to chronic irritation and triggering the cough reflex. The elevated levels of these substances create a state of airway hyper-reactivity, which directly causes the persistent cough.
This chemical accumulation explains why the cough is a class-wide effect of ACE inhibitors. In contrast, the cough associated with inhaled drugs is a simpler physical reaction, where dry powder carriers or propellants cause transient, localized irritation that triggers a brief cough reflex.
Recognizing the Characteristics of a Drug-Induced Cough
A medication-induced cough has distinct characteristics that differentiate it from coughs caused by infections or allergies. The cough is typically dry, meaning it is non-productive and does not produce phlegm or mucus. Patients often report a persistent, irritating tickling or scratchy sensation in the throat preceding the cough.
The timing is a telling sign, as the cough can begin anywhere from a few hours after the first dose to several weeks or even months after a patient begins the medication. This delayed onset often makes the link to the drug less obvious to patients and clinicians. The cough is usually persistent throughout the day and night, though it may worsen when talking or lying down.
Studies suggest that women, non-smokers, and older individuals may be more susceptible to experiencing an ACE inhibitor-induced cough. If a persistent, dry cough develops after starting a new medication and no other cause can be identified, a drug reaction should be strongly considered.
Steps to Take When Medication Causes Coughing
If a persistent cough begins after starting a new prescription, the most important action is to contact the prescribing healthcare provider. Patients should never abruptly stop taking a prescribed medication, especially for conditions like hypertension or heart failure, as this can lead to serious health complications. The provider will assess the timeline and characteristics of the cough to determine if it is likely drug-induced.
The standard diagnostic approach involves discontinuing the suspected drug and monitoring the patient for symptom resolution. If the cough is caused by the medication, it typically begins to subside within one to four weeks after stopping the drug, though full resolution may take up to three months. This process confirms the link between the drug and the cough.
For patients who develop an ACE inhibitor cough, the most common and effective alternative treatment is a switch to an Angiotensin II Receptor Blocker (ARB), such as losartan or valsartan. ARBs work on a different part of the blood pressure regulation pathway. Because they do not affect the bradykinin pathway, they rarely cause coughing, allowing patients to receive comparable therapeutic benefits without the irritating side effect.