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Table 5 List of prescribed drugs known to interact with warfarin, level of interaction and frequency of use

From: Characteristics of patients with thromboembolic disorders on warfarin therapy in resource limited settings

Drug Class

Drug

Frequency (No/%)

Degree of interaction

Effect on INR

Anti-infective Agents

Metronidazole

16 (25)

Major

↑

 

TMP/SMX

9 (14)

Major

↑

 

Fluconazole

4 (6)

Major

↑

 

Levofloxacin

3 (5)

Major

↑

 

Ciprofloxacin

1 (2)

Major

↑

 

Clarithromycin

1 (2)

Major

↑

 

Ceftriaxone

34 (54)

Moderate

↑

 

Amoxicillin/clavulanate

10 (16)

Moderate

↑

 

Azithromycin

9 (14)

Moderate

↑

 

Doxycycline

7 (11)

Moderate

↑

ARVs

Efavirenz

3 (5)

Moderate

↑/↓

 

Nevirapine

1 (2)

Moderate

↓

Anti-TBs

Isoniazid

5 (8)

Moderate

↑

 

Rifampicin

5 (8)

Major

↓

Anti-ulcer drugs

Esomeprazole

26 (41)

Moderate

↑

 

Omeprazole

7 (11)

Moderate

↑

Analgesics

Diclofenac

5 (8)

Major

–

 

Tramadol

21 (33)

Moderate

↑

 

Paracetamol

20 (32)

Moderate?

↑

 

Celecoxib

1 (2)

Moderate

–

CNS drugs

Carbamazepine

2 (3)

Moderate

↓

 

Phenytoin

4 (6)

Moderate

↑/↓

 

Fluoxetine

2 (3)

Moderate

↑

Glucocorticoids

Prednisone

4 (6)

Moderate

↑/↓

 

Dexamethasone

1 (2)

Moderate

↑/↓

 

Hydrocortisone

1 (2)

Moderate

↑/↓

Diuretics

Furosemide

26 (41)

Minor

↑

 

Spironolactone

12 (19)

Minor

↓

CVS drugs

Amiodarone

16 (25)

Major

↑

  1. Key
  2. ↑ Increased INR
  3. ↓ Decreased INR
  4. Amoxiclav Amoxicillin-clavulanic acid combination
  5. SMZ/TMP Trimethoprim/sulfamethoxazole combination
  6. ARVs Antiretroviral agents