There are two PDE5 inhibitors available in New Zealand. These are sildenafil and tadalafil. These were sold initially as Viagra and Cialis, however there have been generic's of both available more recently. The generics are considerably cheaper. When the PDE5 inhibitors aren't effective one alternative is to inject medicine directly into the cavernous spongiosum. The medicines used for this are various combinations and strengths of alprostadil, phentolamine, atropine and papaverine. 

Premature ejaculation is also amenable to medical treatment. Again PDE5 inhibitors may be useful.