Tadalafil is a Better Alternative to Sildenafil for a Patient with Tachycardia Taking Amlodipine
Tadalafil is the preferred phosphodiesterase type-5 (PDE5) inhibitor for patients with tachycardia who are taking amlodipine 5 mg, as it has less impact on heart rate and better pharmacokinetic interactions with calcium channel blockers. 1, 2
Comparison of Tadalafil vs. Sildenafil with Amlodipine
Tadalafil has been specifically studied with amlodipine and shows no clinically significant differences between tadalafil and placebo in subjects taking amlodipine, making it a safer option for patients with tachycardia 1
When sildenafil 100 mg is co-administered with amlodipine (5 mg or 10 mg) to hypertensive patients, it causes a mean additional reduction in supine blood pressure of 8 mmHg systolic and 7 mmHg diastolic, which could potentially worsen tachycardia through compensatory mechanisms 2
Sildenafil has been associated with cases of atrial fibrillation and continuous hypotension in some patients, which would be particularly concerning in someone with pre-existing tachycardia 3
Cardiovascular Safety Profile
Tadalafil has a longer half-life (17.5 hours vs. 4 hours for sildenafil), which results in more stable drug levels and less dramatic hemodynamic fluctuations that could trigger compensatory tachycardia 1
Studies have shown that sildenafil can increase heart rate by approximately 2.1 beats/min when combined with amlodipine, which could exacerbate existing tachycardia 4
The American Heart Association guidelines note that PDE5 inhibitors should be used with caution in patients with certain cardiovascular conditions, but tadalafil's more stable pharmacokinetic profile makes it preferable in patients with tachycardia 5
Important Considerations and Precautions
Both medications are contraindicated with nitrates, with tadalafil having a longer contraindication period (48 hours) compared to sildenafil (24 hours) due to its longer half-life 5
For this patient weighing 195 lbs (approximately 88.5 kg), standard dosing of tadalafil can be used as there is no need for dose adjustment based on weight 1
If the patient experiences symptomatic hypotension with tadalafil, the dose should be reduced or the medication discontinued 1
Monitor blood pressure and heart rate after initiating tadalafil therapy to ensure the patient's tachycardia does not worsen 1
Dosing Recommendations
Start with tadalafil 5 mg daily for erectile dysfunction, which can be increased to 10 mg if needed and tolerated 1
If using tadalafil on an as-needed basis rather than daily, start with 10 mg taken prior to anticipated sexual activity 1
The patient should be advised that tadalafil can be taken without regard to food, unlike sildenafil which may have delayed absorption when taken with high-fat meals 1