Answer: The short version? If you are taking tadalafil to treat erectile dysfunction, you should know that it does not cure erectile dysfunction or increase sexual desire. Tadalafil may cause side effects. One of these is PAH. Furthermore, the longer half-life is the basis for tadalafil’s daily therapeutic use in treating pulmonary arterial hypertension. Tadalafil works on the PDE5 enzyme in the lungs to relax the blood vessels.AdComplete the Online Consultation with our Doctor. Personalize Your Needs. If Appropriate, Get a Prescription for ED from RexMD®. Free Shipping has been visited by 10K+ users in the past monthFree Shipping · Real Doctors · Discreet Packaging · Personalized PlanTypes: MEDICATIONS, Erectile Dysfunction, Prescription, Sexual Health and more. Cialis and generic Cialis, known as tadalafil, are available from online services, along with other ED treatment options for people looking to buy ED medication online. The recommended starting dose for Cialis intended for once daily use is mg, take at the same time each day, without regard to timing of sexual activity. This may be increased to 5mg/day based on need and tolerability. May be taken with or without food. Cialis is available as a generic, under the name tadalafil. 3.