In italiano, questa 'a-' si chiama alfa privativa, per la sua origine dalla lingua greca; a volte diventa 'an-';
Esempi:
aperiodico, (physical phenomena without periodicity)
analcolico (a beverage without alchool)
anaffettivo (without affection)
afasia, (illness: difficulty to utter words)
amnesia (illness or momentary disturbance: without memory)
a stupido (without much intelligence, but with a different origin,
actually 'a' is used to directly refer to someone, Rome dialect)
When the word is long I would rather use the form: 'non /adjective/',
in order to avoid a cumbersome word (my personal opinion).