The tablets your GP has given you are probably antibiotics. Most doctors suggest you try taking these on a daily basis by mouth for a period of four to six months. They work by preventing infection of the extra sebum produced by the sebacious glands in your skin and some antibiotics also appear to directly reduce the amount of sebum your skin produces. If your skin does not get infected it is less likely to produce the yellow pustules which are typical of acne and which can leave scars behind as they heal. If one antibiotic does not work or gives you side effects there are others you can try. Repeated courses of antibiotics may need to be given for several years - as low doses are given this is safe - I usually recommend a two to four month break once or twice a year coinciding with summer as acne tends to improve in the sun.
More recently preparations based on vitamin A (retinoids) have been found to help people with severe acne. These may be appropriate for you if you have tried several courses of different antibiotics with no improvement. Your GP can prescribe topical lotions, gels or creams containing retinoids. However these preparations cause some redness and skin peeling to start with - this settles with time. They cannot be used to treat severe acne covering large areas or on skin that is broken or has eczema. You need to avoid UV light (ie sunbathing or solariums) if using retinoids and use sunblock in sunny weather. They can be very effective if used for several months to reach maximum effect.
If all of these treatments fail to help I would suggest you ask your GP to refer you to a dermatologist. Occasionally treatment with an oral form of retinoid (Isotretinoin) may be suggested. This is a potentially toxic drug which should only be used under the supervision of a dermatologist. It can cause dry skin and eyes, disturb your vision or mood and affect your liver and fat in your blood. Regular blood tests are done whilst you are on such treatment to monitor your liver function and blood fat levels. If there are no side effects it is given for at least 16 weeks and repeat courses are not usually necessary.
Source : http://www.dailymail.co.uk/femail/article-70105/Is-cure-acne.html390