sulfasalazine

CLINICAL USE

Ulcerative colitis Crohn’s disease Rheumatoid arthritis

DOSE IN NORMAL RENAL FUNCTION

Oral: 1–2 g 4 times daily, reduced to 0.5 g 4 times dailyEnema: 3 g at night Suppositories: 0.5–1 g twice daily Rheumatoid arthritis: 0.5 g daily, increased to 1.5 g twice daily

PHARMACOKINETICS

Molecular weight :398.4

%Protein binding :95–99

%Excreted unchanged in urine : 10–15

Volume of distribution (L/kg) :5.9–9.1

half-life – normal/ESRD (hrs) :18/–

DOSE IN RENAL IMPAIRMENT

GFR (mL/MIN)

20 to 50 : Dose as in normal renal function. Use with caution

10 to 20 : Dose as in normal renal function. Use with caution

<10 : Start at very low dose and monitor. Use with caution

DOSE IN PATIENTS UNDERGOING RENAL REPLACEMENT THERAPIES

CAPD :Unlikely to be dialysed. Dose as in GFR <10 mL/min

HD :Unlikely to be dialysed. Dose as in GFR <10 mL/min

HDF/high flux :Unlikely to be dialysed. Dose as in GFR <10 mL/min

CAV/VVHD :Unknown dialysability. Dose as in GFR 10 to 20 mL/min

IMPORTANT DRUG INTERACTIONS

Potentially hazardous interactions with other drugs

Ciclosporin: may reduce ciclosporin levels

ADMINISTRATION

Reconstition

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Route

Oral, rectal

Rate of Administration

–

Comments

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OTHER INFORMATION

15% of a dose of sulfasalazine is absorbed in the small intestine and becomes highly bound to plasma proteins. The remainder is split into sulfapyridine and 5-ASA by colonic bacteria. Sulfapyridine is rapidly absorbed from the colon, whereas 5-ASA is poorly absorbed
Most of a dose of sulfasalazine is excreted in the urine. Unchanged sulfasalazine accounts for 15% of the original dose, sulfapyridine and its metabolites 60%, and 5-ASA and its metabolites 20–33%
Unabsorbed drug is excreted in the faeces In patients with moderate to severe renal impairment, toxicity includes increased risk of crystalluria – ensure high fluid intake

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