Rarely reported side effects include: an erection that will not go away priapism. It’s available in 10 mg and 20 mg tablets. It’s best to check your chosen provider’s site for more information. It’s available in 25 mg, 50 mg, and mg tablets and lasts up to 18 hours. It may be difficult to remain firm despite wanting to have sex. · The generic will be white rather than blue, and it will cost around $32 a pill, half Viagra’s price. Wondering what was in that old prescription bottle? Use the ScriptSave WellRx pill identifier to quickly and easily identify unknown medicines by imprint, shape, number, and color. Our pill identifier helps you verify tablet and capsule products you may have questions about — ensuring you’re taking the right medication.  · Teva sildenafil pills are white, not blue. There’s also a visual difference in the two. Viagra is infamous for being the “little blue pill.”.