Theophylline
CLINICAL USE
Reversible airways obstruction Acute severe asthma
DOSE IN NORMAL RENAL FUNCTION
Oral: depends on preparation used IV: Deteriorating asthma not previously treated with theophylline: 5 mg/kg (250– 500 mg) (as aminophylline) over at least 20 minutes Acute severe asthma: 500 mcg/kg/hour (as aminophylline) adjusted according to plasma-theophylline levels
PHARMACOKINETICS
Molecular weight : 180.2 %Protein binding : 35–60 %Excreted unchanged in urine : 10 Volume of distribution (L/kg) : 0.3–0.7 half-life – normal/ESRD (hrs) : 3–12/Unchanged DOSE IN RENAL IMPAIRMENT
GFR (mL/MIN)
20 to 50 : Dose as in normal renal function 10 to 20 : Dose as in normal renal function <10 : Dose as in normal renal function. See ‘Other Information’ DOSE IN PATIENTS UNDERGOING RENAL REPLACEMENT THERAPIES
CAPD : Not dialysed. Dose as in GFR <10 mL/min HD : Dialysed. Dose as in GFR <10 : mL/ min HDF/high flux : Dialysed. Dose as in GFR <10 : mL/ min CAV/VVHD : Not dialysed. Dose as in normal renal function IMPORTANT DRUG INTERACTIONS
Potentially hazardous interactions with other drugs Antibacterials: increased concentration with azithromycin, clarithromycin, erythromycin, ciprofloxacin, norfloxacin and isoniazid; decreased plasma levels with erythromycin if erythromycin taken orally; increased risk of convulsions if given with quinolones; rifampicin accelerates metabolism of theophylline Antidepressants: concentration increased by fluvoxamine – avoid concomitant use or halve theophylline dose and monitor levels; concentration reduced by St John’s wort – avoid concomitant use Anti-epileptics: metabolism increased by carbamazepine and primidone; concentration of both drugs increased with phenytoin Antifungals: concentration increased by fluconazole and ketoconazole Antivirals: metabolism of theophylline increased by ritonavir Calcium-channel blockers: concentration increased by diltiazem and verapamil and possibly other calcium-channel blockers Tacrolimus: may increase tacrolimus levels Ulcer-healing drugs: metabolism inhibited by cimetidine; absorption possibly reduced by sucralfate ADMINISTRATION
Reconstition
– Route
Oral, IV Rate of Administration
At least 20 minutes or 500 mcg/kg/hour depends on indication Comments
– OTHER INFORMATION
Therapeutic levels should be in the range 10 to 20 : mg/litre (55–110 micromols/litre) 50% of dose is removed by haemodialysis Studies have used it to protect against contrast nephropathy, with conflicting results .
See how to identify renal failure stages according to GFR calculation
See how to diagnose irreversible renal disease
Home
