Prospective observational follow-up study for the study and modeling of the pharmacokinetics of the free fraction of ceftriaxone in patients treated with high doses of ceftriaxone (greater than or equal to 4 grams per day).

A prospective follow-up observational study to study and model the pharmacokinetics of the ceftriaxone free fraction in patients treated with high doses of ceftriaxone (greater than or equal to 4 grams per day). it is a pilot study that has between 10 and 20 patients. This study will not condition the treatment of patients at any time.

The samples will be processed after their extraction. The concentration of the samples will be analyzed using a high-performance gilent infinity liquid chromatograph coupled to a mass spectrometer using positive or negative ionization using electrospray.

Inclusion Criteria:

• Men or women over 55 years of age receiving treatment with high-dose ceftriaxone (minimum 4 grams / day) for any clinical indication in the study period.
• Creatinine <1.5 mg / dL
• The patient must have received at least 48 hours of treatment with the same previous therapeutic regimen to extraction.
• The subject or her representative must give their verbal or written consent to participate in the study. East Consent can be revoked at any time without prejudice to the patient.

The consent it will be recorded in your medical record.

Exclusion Criteria:

• Patients under 55 years of age.
• Creatinine> 1.5 mg / dL
• Patient with less than 48 hours of treatment with high-dose ceftriaxone.
• Subjects with allergy or hypersensitivity to cephalosporins and penicillins.
• Subjects who do not grant or withdraw their consent.
• Patients whose concomitant treatment presents possible interactions with the study medication. The possible interactions will be evaluated by staff of the Pharmacy Service.

Patients treated with ceftriaxone doses equal to or higher 4 grams / day. This study will in no case condition the treatment of patients.