Interval for taking of medicines

Question

Dear CF team,

I (30, CF) am going to take Staphylex® (Flucloxacillin) as a permanent therapy (3x1gram) due to staphylococcus findings. Does it make a difference with regards to the efficiency or formation of resistances if I take it evenly or unevenly throughout the day? Or more exactly: Do I have to take the medication strictly in intervals of 8 hours regarding efficiency or formation of resistances? Or can the interval differ, i.e. once you take it at 8 a.m. and some other time (during week-ends) you take it at 11 a.m. That means: Once there is an interval of 6 hours and some other time the interval is 10 hours.

Greetings and thank you.

Answer

Dear questioner,

Thank you for your question – it is not easy to answer. Generally speaking it is important to take medication (that has to be taken several times a day) evenly thoughout the day; in your case every 8 hours. Furthermore, this is considerably more important for some medicaments than for others. I think that in case of Flucloxacillin it would be possible to have an interval of 7 hours once and 9 hours another time. However, an interval of 10 hours seems too long to me and could have a certain impact on the efficiency against Staph. Aureus. In case of Flucloxacillin it is important that the drug level in the blood is as constant as possible throughout the day and is not below the effective level for too long. If the drug level in the blood is below the effective level it is possible that resistances are formed. However, it should be mentioned that it also happens in hospitals that medication is not administered in the correct intervals. Furthermore, Flucloxacillin should be taken half an hour before a meal. So, you will probably always have to make a compromise because I assume that you do not eat exactly every 7-9 hours.

Best regards
Dr. med. Markus Hofer
Adult CF clinic
University Hospital Zurich

23.04.2010