Tadalafil is an FDA-approved oral medicine sold under the brand name Cialis and in generic forms such as Vidalista. It belongs to the Phosphodiesterase Type 5 (PDE5) inhibitor class and improves penile blood flow, making it a widely prescribed treatment for Erectile Dysfunction (ED), which affects around 50 million men in the US.
Apart from this, it is also used to treat Benign Prostatic Hyperplasia (BPH) and Pulmonary Arterial Hypertension (PAH). While Tadalafil is effective for these conditions, it can interact with certain medicines and cause harmful effects. Key Tadalafil drug interactions include nitrates used for chest pain, blood pressure medicines, and alpha-blockers.
Some of these medicines raise Tadalafil levels and increase side effects, while others lower its levels and reduce its effectiveness. This article explains these interactions in detail, including which medicines are strictly contraindicated and which may be used cautiously under medical supervision. It also covers points to reduce the risk of harmful interactions and use Tadalafil more safely.
What are the key Tadalafil drug interactions?
Key Tadalafil interactions include nitrates, CYP3A4 inhibitors, certain High Blood Pressure medications, and other ED medications. These medicines either lower blood pressure or speed up the body’s elimination of Tadalafil. While some of these combinations are strictly contraindicated, others can be used only after a doctor reviews the dosage, its frequency, timing, and underlying health conditions.
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Nitrates widen blood vessels (vasodilation) and are used to prevent or relieve chest pain (Angina) caused by heart disease. Wider blood vessels reduce resistance to blood flow, which lowers blood pressure. Since Tadalafil also causes vasodilation, taking both together can lead to a sudden, dangerous drop in blood pressure, causing severe dizziness, fainting, a heart attack, or a Stroke.
Avoid nitrates while Tadalafil is active in your body because the combination can cause a dangerous drop in blood pressure. If chest pain occurs, seek emergency help and tell the medical team when you last took Tadalafil. Nitrates should not be given for at least 48 hours afterward unless a doctor decides they are essential and closely monitors you.
Main interacting medicines include:
- Nitroglycerin
- Isosorbide dinitrate
- Isosorbide mononitrate
- Amyl nitrite or butyl nitrite, also called poppers
2. Other PDE5 inhibitors
Other PDE5 inhibitors work exactly like Tadalafil to treat ED or PAH by enhancing blood flow through vasodilatory effects in the penis. As a result, combining them is likely to produce an overdose-like effect, increasing the risk of side effects, such as low blood pressure, dizziness, headache, flushing, vision changes, and, in rare cases, a prolonged erection (for 4 hours or more, known as Priapism).
Strictly avoid combining two or more PDE5 inhibitors since the safety and effectiveness of these combinations have not been established. If Tadalafil is not working for you, contact your doctor for a dose adjustment or medication change, instead of combining multiple ED pills.
Main interacting medicines include:
- Sildenafil
- Vardenafil
- Avanafil
- Udenafil
- Adcirca (brand name Tadalafil for PAH treatment)
3. soluble Guanylate Cyclase (sGC) stimulators
Soluble GC stimulators, like Tadalafil, relax blood vessels and are primarily used for certain forms of PAH or heart failure. Combining them can enhance these vasodilatory effects, leading to severe low blood pressure, dizziness, fainting, and reduced blood flow to vital organs.
Tadalafil must not be used with any GC stimulator. In case it is prescribed alongside, doctors usually advise waiting 48 hours after taking Tadalafil.
Main interacting medicines include:
- Riociguat.
- Vericiguat.
4. Alpha-blockers
Alpha-blockers relax blood vessels and muscles around the prostate and bladder. They are mainly used for managing urinary symptoms of an enlarged prostate and as a second-line treatment for High Blood Pressure in specific cases. Since both Tadalafil and alpha-blockers widen blood vessels, combining them can significantly lower blood pressure, particularly when standing. This can cause dizziness, weakness, or fainting.
Use this combination only after consulting a doctor. For ED, the patient should first be stable on an alpha-blocker, and Tadalafil treatment should begin with a low recommended dose. Combining Tadalafil with an alpha-blocker specifically to treat BPH is not recommended.
Main Cialis interactions are reported with:
- Doxazosin
- Terazosin
- Prazosin
- Tamsulosin
- Alfuzosin
- Silodosin
5. CYP3A4 inhibitors
CYP3A4 is a crucial enzyme found in the liver that metabolizes (breaks down) most medications. CYP3A4 inhibitors slow this enzyme’s activity and influence Tadalafil’s metabolism. This can increase its blood levels and increase the risk of side effects.
The FDA label states that Tadalafil should not exceed 10 mg every 72 hours for as-needed use or 2.5 mg once daily when used with a strong CYP3A4 inhibitor. The exact adjustment will depend on the overall health.
Main interacting medicines include:
- Antifungals: Ketoconazole, Itraconazole
- Antibiotics: Clarithromycin, Erythromycin
- Antiviral medicines: Ritonavir, Cobicistat
6. CYP3A4 inducers
In contrast to CYP3A4 inhibitors, CYP3A4 inducers increase CYP3A4 activity. This can lower Tadalafil blood levels, making the medicine less effective or shortening its duration of action. In such a case, do not increase the Tadalafil dose without medical guidance, as it can still lead to side effects. Make sure to use these medicines together only after consulting a doctor.
Main interacting medicines include:
- Rifampin
- Carbamazepine
- Phenytoin
- Phenobarbital
7. Antihypertensives
The vasodilatory effect of Tadalafil can further reduce blood pressure in combination with medicines used for treating High BP (antihypertensives). This drop is usually mild, but some individuals can experience blurred vision, dizziness, weakness, or fainting, especially when dehydrated or taking several BP medicines.
These combinations are not generally contraindicated, but they should be used after consulting a doctor. Monitoring of BP, dosage, and symptoms can be required. Avoid sudden discontinuation of prescribed BP pill to take Tadalafil.
Main interacting medicines include:
- Amlodipine
- Enalapril
- Metoprolol
- Bendroflumethiazide or Bendrofluazide.
- Angiotensin II Receptor Blockers (ARBs) like Losartan
- Certain beta-blockers, ACE inhibitors, calcium channel blockers, and diuretics
How to reduce the risk of Tadalafil interactions?
Taking a few precautions before and during Tadalafil treatment can minimize the risk of harmful interactions and severe side effects. These precautions are listed as follows:
- Follow the prescribed dose: Take Tadalafil exactly as directed, and do not increase the dose or take more than 1 tablet in 24 hours.
- Avoid prohibited combinations: Do not take Tadalafil with nitrates or sGC stimulators because the combination can cause a dangerous drop in blood pressure.
- Discuss all medications: Inform your doctor if you use alpha-blockers, BP medicines, CYP3A4 inhibitors, or CYP3A4 inducers. In this case, your dosage or treatment plan will likely require adjustment.
- Share your medical history: Let your doctor know if you have any underlying health issues, including heart disease, severe liver or kidney impairment, or Low Blood Pressure. These conditions can increase the risk of side effects or medicine buildup.
- Limit alcohol: Excess alcohol can increase Tadalafil’s blood-pressure-lowering effect, elevating the risk of dizziness, headache, and fainting. Heavy drinking can also make erections more difficult.
- Avoid grapefruit: Just like CYP3A4 inhibitor medications, grapefruit and grapefruit juice can also inhibit CYP3A4. This can raise Tadalafil levels and increase the risk of serious side effects.
- Know when to seek help: Get urgent medical attention for severe Tadalafil side effects, such as chest pain, fainting, sudden vision or hearing loss, or an erection lasting longer than 4 hours.
Conclusion
Tadalafil can interact with medicines that affect blood pressure or change how quickly the body breaks it down. Major Tadalafil drug interactions include nitrates, other PDE5 inhibitors, and sGC stimulators. These are mostly avoided because they can cause a dangerous drop in blood pressure or increase the risk of serious side effects.
Alpha-blockers and antihypertensives can be used only with medical supervision and blood pressure monitoring. Furthermore, consult a doctor before using CYP3A4 inhibitors and inducers, as dose adjustment is usually needed.
To lower interaction risks, follow the prescribed dose, discuss all medicines and health conditions with your doctor, limit alcohol, and avoid grapefruit. Seek urgent medical care for fainting, chest pain, sudden vision or hearing loss, or an erection lasting over four hours.
Frequently Asked Questions
How long do Tadalafil interactions remain in the body?
Tadalafil interactions can remain in the body for around 3-4 days after the last dose. This is because it takes about 17.5 hours for its concentration to be reduced by half in the body. Therefore, it takes about 4 days to be completely flushed from your body.
Can Tadalafil interact with heart medications?
Yes, Tadalafil can interact with heart medications, such as nitrates, including Isosorbide dinitrate and Nitroglycerin. In combination, they can trigger a sharp drop in blood pressure. Tadalafil can also interact with certain blood pressure medications, such as beta-blockers and ACE inhibitors. Always review your full medication list before taking Tadalafil.
What should I do if I accidentally take Tadalafil with an interacting medication?
If you accidentally take Tadalafil with an interacting medicine, discontinue further doses and immediately contact a doctor or poison control center, even if you are feeling well. Provide the name, dosage, and timing of both medications. If you experience chest pain, sudden vision loss, and a prolonged erection, it’s best to call emergency services.
Does grapefruit interact with Tadalafil?
Yes, grapefruit can interact with Tadalafil by inhibiting a liver enzyme (CYP3A4) and affecting its metabolism. It can lead to increased Tadalafil blood levels and risk of side effects. These effects typically include low blood pressure, flushing, and an erection lasting more than 4 hours. It’s best to avoid grapefruit juice when taking Tadalafil.
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