Ciprofloxacin and theophylline: raised theophylline levels and what to do

Theophylline is a long-standing medicine for airway disease. It is taken as tablets or capsules rather than through an inhaler, and the BNF entries for it are mostly about how other medicines change the amount that reaches the body.

Ciprofloxacin is a fluoroquinolone antibiotic. The NHS page covers tablets, liquid, eye drops and ear drops and lists the infections it is used for. It is prescribed by GPs, hospital teams and others for infections where it is considered suitable.

The combination arises most often when a person with a long-term chest condition develops an infection, because infections of the chest, urinary tract and elsewhere are exactly what the antibiotic is used for.

The BNF interaction entry for ciprofloxacin states that ciprofloxacin is predicted to increase the exposure to theophylline. The manufacturer advice recorded is to monitor and adjust the dose, the severity is moderate and the evidence type is theoretical, meaning the prediction is based on how the medicines are handled by the body rather than on a strong body of clinical studies.

The theophylline entries list similar interactions for other antibiotics. Clarithromycin is predicted to increase theophylline exposure with advice to adjust the dose, and for erythromycin the entry states that it decreases the clearance of theophylline, again with dose adjustment advised. This is useful context, because a prescriber choosing an alternative antibiotic needs to be aware that substitution is not automatically risk-free.

Exposure to a medicine is the amount of it present in the body over time. When another medicine slows the way the body clears theophylline, the same dose can lead to a higher level than intended. A rise above the intended level is the thing the monitoring advice is meant to catch.

The sources read for this guide do not give a list of theophylline toxicity symptoms, so this page does not attempt one. If you take theophylline and feel unusually unwell after starting an antibiotic, for example with new nausea, palpitations, shakiness or fits, seek advice the same day, and call 999 for a seizure or collapse.

The NHS ciprofloxacin page separately lists seizures or fits, and a faster or irregular heartbeat, among the reasons to stop and seek help.

Tell the prescriber that you take theophylline or aminophylline before an antibiotic is chosen. A pharmacist can also check this when the prescription is dispensed. The decision may be to choose a different antibiotic, to adjust the theophylline dose, or to arrange a blood test, depending on your situation.

The prescriber may weigh several factors, including your other medicines. Do not change your own dose or stop the medicine on the basis of an online article.

• Name theophylline or aminophylline when you are prescribed any antibiotic.

• Ask the pharmacist to check the combination when you collect it.

• Keep taking your usual dose unless the prescriber changes it.

• Report new symptoms promptly, and keep a note of when the antibiotic was started.

Call 999 if you have a seizure, collapse or sudden severe chest pain or breathlessness. Call NHS 111 or your GP the same day if you feel unwell with palpitations, vomiting or new confusion while taking both medicines. NHS pages for ciprofloxacin also advise stopping and calling a doctor or 111 for tendon pain, mood or behaviour changes and several other symptoms.

Within the NHS, GP practices, respiratory teams and pharmacists manage this combination. Private clinicians use the same references, so the same list of medicines should be given to them.