• Hypersensitivity against diclofenac
• History of allergic reactions (bronchospasm, shock, rhinitis, urticaria) following the use of aspirin or another NSAID
• Third-trimester pregnancy
• Active stomach and/or duodenal ulceration or gastrointestinal bleeding
• Inflammatory bowel disease such as Crohn’s disease or ulcerative colitis
• Severe insufficiency of the heart (NYHA III/IV)
• Pain management in the setting of coronary artery bypass graft (CABG) surgery
• Severe liver insufficiency (Child-Pugh Class C)
• Severe renal insufficiency (creatinine clearance <30 ml/min)
• Caution in patients with pre-existing hepatic porphyria, as diclofenac may trigger attacks
• Caution in patients with severe, active bleeding such as cerebral hemorrhage
• NSAIDs in general should be avoided during dengue fever, as it induces (often severe) capillary leakage and subsequent heart failure.
• Caution in patients with fluid retention or heart failure.
• Can lead to onset of new hypertension or worsening of pre-existing hypertension
• Can cause serious skin adverse events such as exfoliative dermatitis, Stevens-Johnson Syndrome (SJS), and toxic epidermal necrolysis (TEN), which can be fatal.

• Known hypersensitivity to trimethoprim, sulphonamides or any other ingredients in the formulations
• Pregnancy – especially in the period prior to birth
• Severe hepatic failure, marked liver parenchymal damage or jaundice.
• Serious haematological disorders and porphyria (due to the sulfonamide component of the preparation).
• Severe renal insufficiency (CrCl <15 ml/min) where repeated measurements of the plasma concentration cannot be performed
• Co-trimoxazole should not be given to neonates during the first 6 weeks, except for the treatment/prophylaxis of pneumocytosis jiroveci (P. carinii) in infants of four weeks of age or greater.

Allopurinol should not be given to people who are allergic to it.

Drug interactions are extensive, and are as follows:

• Azathioprine and 6-mercaptopurine: Azathioprine is metabolised to 6-mercaptopurine which in turn is inactivated by the action of xanthine oxidase – the target of allopurinol. Giving allopurinol with either of these drugs at their normal dose will lead to overdose of either drug; only one-quarter of the usual dose of 6-mercaptopurine or azathioprine should be given;
• Didanosine: plasma didanosine Cmax and AUC values were approximately doubled with concomitant allopurinol treatment; it should not be co-administered with allopuroinol and if it must be, the dose of should be reduced and the person should be closely monitored.

Allopurinol may also increase the activity or half-life of the following drugs, in order of seriousness and certainty of the interaction:

• Ciclosporin
• Coumarin anticoagulants (reported rarely, but is serious when it occurs)
• Vidarabine
• Chlorpropamide
• Phenytoin
• Theophylline
• Cyclophosphamide, doxorubicin, bleomycin, procarbazine, mechlorethamine

Co-administration of the following drugs may make allopurinol less active or decrease its half-life

• Salicylates and medicines that increase the secretion of uric acid
• furosemide (see more on diuretics below)

Co-administration of the following drugs may cause hypersensitivity or skin rash:

• Ampicillin and amoxicillin
• Diuretics, in particular thiazides, especially in renal impairment
• Angiotensin-converting-enzyme inhibitors (ACE inhibitors)

Absolute contraindications include:

• Circulatory
• CNS depression
• Coma
• Drug intoxication
• Bone marrow suppression
• Phaeochromocytoma
• Hepatic failure
• Active liver disease
• Previous hypersensitivity (including jaundice, agranulocytosis, etc.) to phenothiazines, especially chlorpromazine, or any of the excipients in the formulation being used.

Relative contraindications include:

• Epilepsy
• Parkinson’s disease
• Myasthenia gravis
• Hypoparathyroidism
• Prostatic hypertrophy
• Very rarely, elongation of the QT interval may occur, increasing the risk of potentially fatal arrhythmias.