If you do not currently have the right to state healthcare (e.g. through a state pension) and you are currently living and have been on the padrón for over 1 year in Murcia, then this is the option for you. The convenio is the Spanish Government’s health insurance scheme through which those who don‘t have access to state-provided healthcare can join to get cover. The scheme is nation-wide, but managed by each autonomous region. Policy holders under 65, including children, will pay a monthly quota of €60 each and be able to receive access to state healthcare anywhere in Spain, regardless of pre-existing conditions. However, prescription costs are not included so you would pay the full cost for medicine from the pharmacy. For further information, please see the Murcia Government website here. You will need to get an application form from your local healthcare centre and apply in writing to regional offices stated on the back of the form.
Unsure if you are entitled? Check out http://www.healthcareinspain.eu.