The study's objective will be to evaluate the gabapentine efficiency in orally and long term used after painfully surgeries.

This study will be: controlled, prospective, randomized and double blind.

Its main objective will be to evaluate the pre and postoperative Gabapentin efficiency in orally doses and long term used of it in order to prevent or decrease persistent postoperative pain (PPP) in surgeries with high incidence of it (Pain). Patients will be randomly divided in two branches; one of them will take 600 mg of Gabapentin twice a day and the other group will take Placebo (twice a day also).

Both groups of patients will have to take one pill the day before the surgery (300 mg) and other pill on the surgery day (300mg). After that, the patients will have to continue this treatment during 30 days (two doses per day of Gabapentin or placebo).

After the surgery and after taking the second pill, it will be evaluated:

postoperative sharp pain, sickness, vomiting, sedation and adverse effects.

Patients will be evaluated in the pain treatment office (consulting room) the following times:

1. 30 days after the surgery. (taking drugs suspended)
2. 3 month after the surgery.
3. 6 months after the surgery.
4. 12 months after the surgery

This monitoring treatment will be done in order to evaluate the presence or absence of persistent postoperative pain (PPP).

Inclusion Criteria:

• Patients that require persistent painfully surgeries such as breast surgeries (mastectomies and breast implants), herniorrhaphies (not laparoscopical) unilateral or bilateral, amputations of upper and lower limbs and chest surgeries (thoracotomy, thoracoscopy , sternotomies).
• Patients that had already signed the informed consent.
• Patients aged between 21 and 75.
• ASA I - II _ III (Classification system that the American Society of Anesthesiologists (ASA) uses to estimate the anesthesiology risk that patients may suffer)
• BMI, not more than 35 Kg/m2.

Exclusion Criteria:

• Pregnant women
• Patients that suffer liver and renal failure (plasma creatinine over 1.5 mg/ml or creatinine clearance less than 60 ml/min),heart failure or neurological dysfunction.
• Diabetic patients
• Gabapentine allergic patients

Cuando el paciente dé su consentimiento, será reclutado y randomizado a un grupo control (recibirá placebo) o a un grupo tratamiento (recibirá gabapentin) Los pacientes recibirán una técnica anestésica habitual, basadas en drogas endovenosas mediante el método TCI (target controlled infusión). Con este método se unifica el uso de las drogas anestésicas, que son utilizadas de acuerdo a sexo, edad, género, peso y altura en cada uno de los pacientes.

La analgesia será la convencional para cada cirugía y se continuará con el uso de catéteres epidurales, para analgesia en aquellas intervenciones donde su aplicación sea habitual.