Elderly patients and inflammatory bowel disease

Table 3 Drug interactions of medications used in the treatment of inflammatory bowel disease relevant to elderly patients

IBD drug	Drug interaction
Aminosalicylates	Increase levels of thiopurine metabolite 6-TGN through weak TPMT inhibition
	Interact with warfarin and increase INR (particularly Olsalazine)
Metronidazole	Increases levels of: Simvastatin; Calcium channel blockers; sildenafil and lithium
	Antabuse (disulfuram) like reaction with ethanol
	Increased metabolism and consequent clearance when co-administered with phenytoin and phenobarbitone
	Potentiates Warfarin: May increase INR
Ciprofloxacin	NSAIDs: Risk of seizures may be increased
	Theophylline: Levels may increase
	Potentiates Warfarin: May increase INR
	Phenytoin: Levels of phenytoin may decrease
Corticosteroids	Antidiabetic agents: Hypoglycaemic effects may be decreased
	Calcium channel blockers: May increase corticosteroid levels
	Diuretics: Hypokalaemic effects increased
	Warfarin: May increase anticoagulant effects
Thiopurines	Allopurinol: Can lead to bone marrow toxicity
	Aminosalicylates: May lead to increased toxicity and cause leukopenia/myelosuppression
	Clotrimazole, angiotensin–converting enzyme inhibitors: increased risk of leucopenia
	Warfarin: Anticoagulant effect may decrease
Methotrexate	Loop diuretics: Can alter methotrexate concentrations and vice versa
	NSAIDs: Bone marrow suppression and gastrointestinal toxicity
	Penicillins: Increase methotrexate concentration
	Tetracyclines: Increase methotrexate toxicity
	Theophylline levels may be increased
Cyclosporine	Ciprofloxacin, gentamicin and vancomycin: Potentiate renal dysfunction
	Anti-inflammatory drugs and histamine-2 blockers: Potentiate renal dysfunction
	Azithromycin, clarithromycin: Increase cyclosporine levels
	Allopurinol: Increases cyclosporine levels
	Rifampicin: Decreases cyclosporine levels
	Phenytoin, phenobarbital and carbamazepine: Decrease levels of cyclosporine
	Grapefruit juice: Increases absorption of cyclosporine

IBD: Inflammatory bowel disease; NSAIDs: Nonsteroidal anti-inflammatory drugs; 6-TGN: 6-thioguanine nucleotide; TPMT: Thiopurine S-methyltransferase; INR: International normalised ratio.