Hi, what is the most effective treatment to lighten Post Inflammatory Hyperpigmentation/ dark spots on face due to acne. Thanks?

Manage the acne. Depigmentation bleach creams like hydroquinone risk disfiguring you. At age 17, you have a duty to yourself to take charge of treating your acne. It's a chronic, non-lifeastyle-related disease that will remit on its own when it decides to, and that you should treat aggressively until then. If topical benzoyl peroxide has not cleared you in two weeks, you'll need your physician's prescription Rx.
See a dermatologist. Most important= control acne. May require oral therapy. Protect from UV with sunscreen every AM. Retinoid every night: tretinoin or adapalene. Patience. Will need months, probably years, but, with treatment you will look good. Avoid harsh scrubbing which aggravates post-inflammatory pigment. Acne is not a hygiene problem. Even blackheads are not dirt. Not a diet problem, not a stress problem. Not.

Related Questions

Can Meladerm reduce pink/red/brown (post-inflammatory hyperpigmentation) spots, from acne that isn't there anymore?

No need for this. You don't likely need lightening agents for for post-acne lesions. They should fade over time as long as you as using a good moisturizer and sun block, like Purpose Lotion. Scarring may indeed be part of your problem; if so, see a dermatologist. Meladerm contains several things that have not undergone clinical trials.

How can I reduce post inflammatory hyperpigmentation on my back after acne is gone?

Many ways. The inexpensive approach is use high spf sunscreen to prevet further injury. Then start vitamin c to interfere with the production of melanin. Give it several months. It does not improve quickly. If you are more impatient, and have extra cash, see if you can get something like Retin-A from your doctor.
Chemical peel. Even hydroquinone products and non hq based products to lighten skin. Ipl can work.