Intravenous Medications

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— Names (chemical, commercial, hospital slang), notable side effects (e.g., Tobra & deafness), dosages

Antibiotics: Tobramycin (Tobra); Nafcillin; Cephtasamine; Ticarcillian (Ticar); timentin; Fortaz. – I’m on Tobra 170mg Q/8 hours and Fortaz 2mg diluted in 10ml of Sodium Chloride Q/8. I have noticed that immediately following, if not during the Fortaz, I get a splitting head ache in the back of my head. It usually lasts about an hour, and some Motrin usually helps. – Imipenem (“…makes me nauseated and gives me blood in my urine..”; doc prescribed Benedryl capsule 30 minutes before starting Imipenem to relieve nausea; different doc prescribed hydroxyzine which is similar to Benedryl).

A pharmacist says: “Primaxin (Imipenem) is a Beta-lactam antibiotic similar to the penicillins and cephalosporins. At higher doses, it can cause a lot of nausea. Oral doses of phenergan (promethazine) given about 30 minutes before the dose should take care of the nausea. Another highlight of Primaxin is that it often causes resistant strains of Pseudomonas to develop. For that reason, a person with CF does not really want to be on it for too long at a time, unless it is absolutely necessary”.

Journal references: Ansorg, 1990 Comparison of inhibitory and bactericidal activity of antipseudomonal antibiotics against Pseudomonas aeruginosa isolates from cystic fibrosis patients. Chemotherapy 36, 222-9 (1990) “90249250 ; Pedersen, 1985 Imipenem/cilastatin treatment of multiresistant Pseudomonas aeruginosa lung infection in cystic fibrosis. J Antimicrob Chemother 16, 629-35 (1985); Krilov, 1985 Imipenem/cilastatin in acute pulmonary exacerbations of cystic fibrosis. Rev Infect Dis 7 Suppl 3, S482-9 (1985); Reed, 1985 Pharmacokinetics of imipenem and cilastatin in patients with cystic fibrosis. Antimicrob Agents Chemother 27, 583-8 (1985).

Bronchodialaters * Steroids

Is bacteria growing in my lungs? If so, how do they know what drug to use?

They are virtually guaranteed to find something growing in there. It’s very normal. The question is, what do you do about it if anything. As far as what drug is used to treat the infection, it depends on what drug will kill the bacteria (pretty simple). In the lab, they’ll culture the little bacteria in little petri dishes and in each one they’ll put a little of an individual antibiotic. And, voila, a few days later, whatever dishes are full of little dead bacteria, that’s the drug that’ll be suggested. This is called a ‘drug sensitivity’.

That brings up the next point, in general, whatever iv drug is used, the bacteria eventually build up a resistance to. Some take longer than others for some reason, Tobramycin is generally good for a long time. For some reason, the little buggers can’t figure out how to survive in an environment full of Tobramycin. But on the other hand, a drug like cipro. (which happens to be oral, but the idea’s the same) you become resistant to pretty quickly. I was recommended to stay on it for 10-14 days only. After that, it loses its effect.

Another thing to look into is side effects. For example, Tobra, as wonderful as it is (and ubiquitous), is liver-toxic and can cause a lot of problems.

About Tobra

Tobra is probably the most common antibiotic used for PWCF who’ve got a pseudomonas infection. Prior to pseudomonas infection, other far less worrisome antibiotics suffice to kill Staph and the other less dangerous bacteria that affect young children with CF. Tobra is in a family of antibiotics called the amino glycosides, which also includes Gentamicin and Vancomycin. Tobra is often the drug of choice because it seems to work well against Pseudomonas, especially when combined with a non-amino glycoside antibiotic. It is usually given IV 3-X-day for 10-21 days as part of a “clean-out/tune-up”, but can also be given at several different doses by aerosol. Some people use it by aerosol just for exacerbations, in hopes of avoiding IV therapy, and some people use it as a daily aerosol all the time. Tobra sounds like a wonderful drug, however, it can have dangerous side-effects. Blood levels drawn both before and after IV doses must be measured frequently and kept within a narrow range. If too much Tobra is delivered kidney damage/failure and/or severe hearing loss can result; if too little is delivered the efficacy is poor, and resistant organisms are developed. Aerosolized Tobra seems not to have any side-effects other than local irritation, as it is not absorbed from the lung into the bloodstream to any significant degree (however, most people think that Tobra aerosols taste and smell awful). Aerosolized Tobra is also not as effective as an all-out IV clean-out.

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