Prophylaxis of pneumocystis jirovecii

QUESTION 1

Part A:

• 1:5 ratio means the total number of ‘parts’ of mixture is six (1+5=6)
• The suspension is 480 mg/5 ml
• In 5 ml each ‘part’ = 480 mg/6 parts = 80 mg per part
• One part trimethoprim to five parts sulfamethoxazole means 5 ml contains 80 mg trimethoprim
• This 80 mg is contained within 5 ml
• 80 mg/5 ml = 16 mg per ml

Part B:

• Five parts of sulfamethoxazole at 80 mg per part = 400 mg per 5 ml
• 400 mg/5 ml = 8 000 mg/100ml = 8 g/100ml = 8%w/v

QUESTION 2

Part A:

• 5.5 kg gives an estimated surface area of 0.3 m² from the BNF table
• 450 mg/m2 x 0.3m2 = 135 mg per dose

Part B:

• 5.5 kg gives an estimated surface area of 0.3m² from the BNF table
• 450 mg/m² x 0.3m² = 135 mg per dose
• 240 mg per 5 ml = 48 mg per ml
• 135 mg per dose/48 mg per ml = 2.812 5 ml
• 2.8 ml are needed per dose

QUESTION 3

Part A:

• 5.5 kg x 120 mg per kg = 660 mg per day
• 660 mg day split into 3 daily doses = 22 mg/dose

Part B:

• 480 mg per 5 ml = 96 mg per ml
• 220 mg/96 mg per ml = 2.29 ml
• 2.3 ml are needed per dose