Combining the treatments has a cumulative effect — penile injection therapy makes your erections hard, and adding Viagra makes them harder and even more long-lasting. The facts: No, taking Viagra to enhance your bedroom performance won’t make it harder for you to see your partner. Kamagra can be a very tempting offer for men shopping on line for impotence medication because of the very low cost compared to the cost genuine Viagra. “To my knowledge, Viagra has never caused a prolonged erection by itself,” Dr. Montague says.