Tadalafil and Chlordiazepoxide: Can They Be Taken Together?

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At a glance

What is tadalafil and chlordiazepoxide?

Tadalafil (often known by the brand name Cialis) is a phosphodiesterase type 5 (PDE5) inhibitor licensed in the UK to treat erectile dysfunction [4]. It works by relaxing blood vessels in the penis, allowing increased blood flow when you are sexually aroused. Tadalafil is available as an on-demand treatment (10 mg or 20 mg taken at least 30 minutes before sex, with effects lasting up to 36 hours) or as a daily low-dose tablet (2.5 mg or 5 mg) [4]. It requires sexual stimulation to work and does not cause spontaneous erections.

Chlordiazepoxide is a benzodiazepine medicine used to treat short-term anxiety and symptoms of alcohol withdrawal. It works by enhancing the calming effects of a natural brain chemical called GABA (gamma-aminobutyric acid), which helps reduce excessive nerve activity. Chlordiazepoxide can cause drowsiness, dizziness, and reduced alertness, and it is usually prescribed for short periods because of the risk of dependence. It is not a treatment for erectile dysfunction, but some men may be prescribed both medicines for separate health conditions.

Can you take tadalafil and chlordiazepoxide together?

There is no absolute contraindication to taking tadalafil and chlordiazepoxide together, meaning they are not medicines that must never be combined (unlike tadalafil with nitrates, for example). No major direct pharmacological interaction between tadalafil and chlordiazepoxide is commonly reported in standard drug interaction databases. However, both medicines can have effects that may add together and increase the risk of side effects such as dizziness, drowsiness, and low blood pressure [3][4].

Tadalafil can lower blood pressure slightly as part of its mechanism of action, and chlordiazepoxide can cause sedation and affect coordination. When taken together, these effects may be more noticeable, particularly when you first start treatment or if your dose is increased. Your prescriber will assess your individual circumstances, including your current dose of chlordiazepoxide, any other medicines you take, and your overall health, to decide whether tadalafil is suitable for you. It is essential to declare all your current medicines—prescription, over-the-counter, and herbal—during your online consultation so that the prescriber can make a safe, informed decision.

How the interaction works

Tadalafil relaxes smooth muscle in blood vessels throughout the body, which can lead to a modest drop in blood pressure. Chlordiazepoxide acts on the central nervous system to produce calming and sedative effects, and it can also cause dizziness or light-headedness, particularly when standing up quickly. While these medicines work through different mechanisms and do not directly interfere with each other's metabolism or action, their side effects can overlap. If you experience dizziness or feel faint, especially when moving from sitting to standing, this may be more pronounced when both medicines are in your system. The prescriber will take this into account and may recommend starting tadalafil at a lower dose if appropriate.

What your prescriber checks before prescribing tadalafil and chlordiazepoxide

When you complete an online consultation at Cured Pharmacy, a UK-registered prescriber reviews your medical history and current medicines to ensure tadalafil is safe and suitable for you [1][2]. They will check for any contraindications—conditions or medicines that mean tadalafil should not be used—such as nitrates (GTN spray, isosorbide mononitrate or dinitrate), nicorandil, riociguat, or recreational drugs known as 'poppers' (amyl or alkyl nitrites). These combinations can cause a dangerous drop in blood pressure and must be avoided [3][4].

The prescriber will also review your chlordiazepoxide dose and how long you have been taking it, along with any other medicines that affect blood pressure or cause sedation. They will ask about your cardiovascular health, including any history of heart attack, stroke, angina, or heart failure, because sexual activity itself carries some physical exertion and tadalafil is not suitable if your heart condition is unstable [2][4]. If you take other blood-pressure medicines (such as ACE inhibitors, beta-blockers, or calcium-channel blockers), the prescriber will consider the combined blood-pressure-lowering effect. They may recommend starting on the lowest effective dose of tadalafil and monitoring how you feel.

What you need to know

• No major direct interaction between tadalafil and chlordiazepoxide is commonly reported.
• Both medicines can cause dizziness or drowsiness, so your prescriber reviews your full medication list.
• Tadalafil is not suitable with nitrates, nicorandil, riociguat, or poppers—always declare all medicines.
• Limit alcohol and avoid grapefruit juice while taking tadalafil to reduce side effects.
• Seek urgent help for an erection lasting over four hours or sudden vision or hearing loss.

Practical advice for taking tadalafil and chlordiazepoxide safely

If your prescriber approves tadalafil while you are taking chlordiazepoxide, follow their instructions carefully. Take tadalafil exactly as prescribed—on-demand tablets (10 mg or 20 mg) should be taken at least 30 minutes before sexual activity, and the effect can last up to 36 hours [4]. Do not take more than one dose in 24 hours. If you have been prescribed daily tadalafil (2.5 mg or 5 mg), take it at the same time each day, regardless of when you plan to have sex. Tadalafil requires sexual stimulation to work; it will not cause an erection on its own.

Be cautious about activities that require full alertness, such as driving or operating machinery, especially when you first start tadalafil or if you notice increased drowsiness or dizziness. Avoid drinking large amounts of alcohol, as this can worsen erectile dysfunction, increase the risk of side effects such as dizziness and low blood pressure, and reduce the effectiveness of tadalafil [3][4]. Grapefruit juice can raise tadalafil levels in your blood, so it is best to avoid it. If you feel dizzy or light-headed, sit or lie down until the feeling passes, and get up slowly from sitting or lying positions.

When to contact your doctor or pharmacist

Contact your GP or pharmacist if you experience persistent dizziness, fainting, or any side effects that concern you while taking tadalafil and chlordiazepoxide together. If you develop chest pain during or after sexual activity, stop and seek medical advice—do not take more tadalafil, and tell the healthcare professional that you have taken it, as some treatments for chest pain (nitrates) must not be used within 48 hours of tadalafil [4]. Seek urgent help (call 999 or go to A&E) if you have an erection lasting more than four hours (priapism), sudden loss of vision or hearing, or severe chest pain. Do not stop taking chlordiazepoxide suddenly without medical advice, as benzodiazepines need to be reduced gradually to avoid withdrawal symptoms.

Other medicines and conditions to consider with tadalafil and chlordiazepoxide

In addition to chlordiazepoxide, your prescriber will check for other medicines that can interact with tadalafil. Alpha-blockers (such as doxazosin, tamsulosin, alfuzosin, or terazosin), used for prostate symptoms or high blood pressure, can cause a significant drop in blood pressure when combined with tadalafil [3][4]. If you take an alpha-blocker, you should be stable on it before starting tadalafil, and your prescriber will usually recommend the lowest dose of tadalafil. Potent CYP3A4 inhibitors—medicines such as ritonavir, cobicistat (found in some HIV treatments), ketoconazole, itraconazole, or clarithromycin—can raise tadalafil levels, requiring dose adjustments or avoidance [4].

CYP3A4 inducers, including rifampicin, carbamazepine, phenytoin, and St John's wort, can reduce tadalafil's effectiveness by speeding up its breakdown in the body [4]. If you take any of these, tell your prescriber during the consultation. Tadalafil is not suitable for everyone: it should not be used if you have very low blood pressure, severe liver or kidney disease, a recent heart attack or stroke, unstable angina, severe heart failure, or a history of non-arteritic anterior ischaemic optic neuropathy (NAION), a rare cause of sudden vision loss [2][4]. Your prescriber will assess your suitability based on your full medical history.

When to get urgent help

• An erection lasting more than four hours (priapism)—go to A&E immediately
• Sudden loss of vision or hearing—stop tadalafil and seek urgent medical advice
• Chest pain during or after sex—stop activity, do not take more tadalafil, and call 999
• Severe dizziness, fainting, or feeling very unwell—seek same-day medical advice
• Allergic reaction (rash, swelling of face or throat, difficulty breathing)—call 999

Call 999 or go to A&E in an emergency, or contact NHS 111 for urgent advice.

Why erectile dysfunction matters and when to see your GP about tadalafil and chlordiazepoxide

Erectile dysfunction is very common—it affects around half of men aged 40 to 70 to some degree—and it is often treatable [1][10]. ED can be an early warning sign of underlying health conditions such as cardiovascular disease, diabetes, or high blood pressure, so it is important to see your GP if you are experiencing new or worsening erection problems [1][2]. Your GP can investigate possible causes, check your cardiovascular health, review your medicines (including chlordiazepoxide, which can sometimes contribute to sexual difficulties), and refer you for specialist assessment if needed.

Anxiety and stress, which chlordiazepoxide is prescribed to manage, can themselves contribute to erectile dysfunction. Addressing the underlying anxiety, through talking therapies, lifestyle changes, or appropriate medication, may improve ED symptoms. If you are taking chlordiazepoxide long-term, discuss this with your GP, as benzodiazepines are usually recommended for short-term use only. Your GP or prescriber can help you find the right balance of treatments for both your mental health and sexual health. At Cured Pharmacy, our online consultation allows a UK prescriber to review your full medical history and current medicines, including chlordiazepoxide, to determine whether tadalafil or another ED treatment is safe and appropriate for you.

Lifestyle measures to support ED treatment

Alongside any prescribed treatment, lifestyle changes can improve erectile function and overall health [1][2]. Maintaining a healthy weight, eating a balanced diet, exercising regularly, stopping smoking, and reducing alcohol intake all support better erections and cardiovascular health. Managing stress and anxiety—through relaxation techniques, counselling, or cognitive behavioural therapy—can also help, particularly if psychological factors are contributing to your ED. Open communication with your partner about ED and treatment can reduce performance anxiety and improve your sexual relationship. These measures work best when combined with appropriate medical treatment, and your GP or pharmacist can offer further advice tailored to your situation.