Medications Contraindicated with Tamsulosin (Omnic Ocas)
Strong CYP3A4 inhibitors such as ketoconazole are contraindicated with tamsulosin (Omnic Ocas) due to significant risk of increased tamsulosin exposure and potential hypotensive effects. 1
Absolute Contraindications
- Hypersensitivity to tamsulosin or any component of the formulation (reactions may include skin rash, urticaria, pruritus, angioedema, and respiratory symptoms) 1
- Strong inhibitors of CYP3A4 (e.g., ketoconazole) - concomitant use can increase tamsulosin concentration by 2.8 times, significantly increasing risk of adverse effects 1
- Other alpha-adrenergic blocking agents - combined use increases risk of severe hypotension 1
Medications Requiring Caution
Moderate to Strong CYP Inhibitors
- Moderate CYP3A4 inhibitors (e.g., erythromycin) - may increase tamsulosin levels 1
- Strong CYP2D6 inhibitors (e.g., paroxetine) - can increase tamsulosin exposure by 1.6 times 1
- Moderate CYP2D6 inhibitors (e.g., terbinafine) - may increase tamsulosin levels 1
- Cimetidine - can decrease tamsulosin clearance by 26% and increase AUC by 44% 1
Cardiovascular Medications
- PDE5 inhibitors (e.g., sildenafil, tadalafil, vardenafil) - concomitant use may cause symptomatic hypotension due to additive vasodilatory effects 1, 2
- Tadalafil with doxazosin showed significant blood pressure reduction, but tadalafil with tamsulosin showed minimal interaction 2
- Warfarin - caution advised due to potential interaction, though definitive studies are lacking 1
Special Considerations
- Combination therapy with anticholinergics (e.g., solifenacin, oxybutynin) or beta-3 agonists (e.g., mirabegron) is generally safe and effective for managing persistent storage symptoms 3, 4
- Antihypertensive medications (nifedipine, atenolol, enalapril) generally do not require dosage adjustments when used with tamsulosin 1, 5
- Patients with moderate hepatic impairment do not require dosage adjustment, but tamsulosin has not been studied in severe hepatic impairment 1
- Patients with renal impairment do not require dosage adjustment, but end-stage renal disease patients have not been studied 1
Clinical Implications and Monitoring
- Monitor for orthostatic hypotension, especially when initiating therapy or when used with other medications that may lower blood pressure 1
- Be aware of Intraoperative Floppy Iris Syndrome (IFIS) risk during cataract or glaucoma surgery in patients taking or previously treated with tamsulosin 1
- Patients with concomitant hypertension may require separate management of their hypertension, as tamsulosin should not be assumed to provide optimal management of hypertension 3
- Monitor for priapism, a rare but serious adverse effect associated with tamsulosin use 1
Tamsulosin is generally well-tolerated with a favorable safety profile compared to non-selective alpha blockers, with less risk of orthostatic hypotension but higher incidence of ejaculatory dysfunction 3, 6.