P-AMINOSALICYLIC ACID
Please note p-aminosalicylic acid is not licensed in the UK.
DOSAGE
Adults: 150mg/kg/day in two to four divided doses (oral). Usual dose is 8-12g per day.
Children: 200-300mg/kg/day (see dose banding table below for children weighing up to 30kg).
Note: P-aminosalicyclic acid is only available in 4g sachets. The GranuPAS® brand comes with a dosage scoop graduated in milligrams to aid dosing in children. If Paser® is used, a scoop is not available. In order to give part of a sachet, flatten out the packet, so that the granules are spread evenly in the packet. Cut the packet to the approximate dose required – i.e. cut into halves for 2g doses, and into quarters for 1g doses. Discard the remaining unused portions of the packet.
The GranuPAS®/ Paser® brand of p-aminosalicyclic acid should be prescribed, since these have an acid-resistant coating, preventing stomach gastric acid from degrading the drug to m-aminophenol, a known hepatotoxin. The enteric coating therefore prevents acid degradation of the drug in the stomach, and releases the drug in the small intestine where neutral pH causes fast dissolution of the enteric coating.
The granules of p-aminosalicyclic acid should be sprinkled on to an acidic food such as applesauce or yogurt, or mixed in acidic juices such as tomato, grape, grapefruit, cranberry, apple, or orange. The granules must not be chewed, and must not be mixed with neutral pH food or drink.
Take p-aminosalicyclic acid with food to reduce gastrointestinal adverse effects.
PREPARATIONS
Oral: 4g granules per sachet (unlicensed medicine).
DRUG LEVEL MONITORING
ADVERSE EFFECTS
COMMON:
Gastrointestinal: Nausea, vomiting, diarrhoea, abdominal pain.
Immunological: Hypersensitivity reactions (5-10%) including rash & fever.
SERIOUS:
Metabolic: Hypothyroidism.
Haematological: Haemolytic anaemia (patients with G6PD deficiency), agranulocytosis, eosinophilia, leucopaenia, and thrombocytopaenia.
Hepatic: Acute hepatitis (rare).
ADVERSE EFFECTS: MONITORING
TFTs: 3 monthly (if being given in combination with prothionamide, increase to monthly)
Routine tests as per generic MDR-TB treatment monitoring guidelines.
INTERACTONS
Antacids: Fast dissolution of acid-resistant coating, resulting in early release of p-aminosalicyclic acid into the stomach. However as the stomach gastric acid will have been neutralised, degradation of p-aminosalicyclic acid to m-aminophenol will not occur. No dose adjustments required, however administration of p-aminosalicyclic acid in acidic food or drinks is not required.
Digoxin: Possible decrease in digoxin absorption. Monitor digoxin serum concentrations.
Prothionamide: increased risk of hypothyroidism, possible increased risk of hepatoxicity.
Rifamycins: reduced absorption of rifamycins. Give 8-12 hours apart.
This information is not inclusive of all drug interactions. Please discuss with a pharmacist.
CONTRA-INDICATIONS & CAUTIONS
Contraindications:
Hypersensitivity: To p-aminosalicylic acid, or to aspirin.
Renal Disease: Manufacturer advises to avoid in severe renal failure, as an inactive metabolite is renally excreted. May worsen acidosis and/or crystalluria in severe renal failure.
Cautions:
Pregnancy: Use in pregnancy has not been studied/
Breast-feeding: P-aminosalicylic acid is secreted into breast milk at 1/70th of the maternal plasma concentration.
LABORATORY INFORMATION
Please find up to date information at www.assayfinder.com regarding individual providers of drug level monitoring tests. Click on the provider to discover contact details. Turnaround time varies depending on the test and whether it is run locally or sent to an external lab. By contacting laboratories in advance, turnaround time can significantly be reduced.
DOSAGE
Adults: 150mg/kg/day in two to four divided doses (oral). Usual dose is 8-12g per day.
Children: 200-300mg/kg/day (see dose banding table below for children weighing up to 30kg).
Note: P-aminosalicyclic acid is only available in 4g sachets. The GranuPAS® brand comes with a dosage scoop graduated in milligrams to aid dosing in children. If Paser® is used, a scoop is not available. In order to give part of a sachet, flatten out the packet, so that the granules are spread evenly in the packet. Cut the packet to the approximate dose required – i.e. cut into halves for 2g doses, and into quarters for 1g doses. Discard the remaining unused portions of the packet.
The GranuPAS®/ Paser® brand of p-aminosalicyclic acid should be prescribed, since these have an acid-resistant coating, preventing stomach gastric acid from degrading the drug to m-aminophenol, a known hepatotoxin. The enteric coating therefore prevents acid degradation of the drug in the stomach, and releases the drug in the small intestine where neutral pH causes fast dissolution of the enteric coating.
The granules of p-aminosalicyclic acid should be sprinkled on to an acidic food such as applesauce or yogurt, or mixed in acidic juices such as tomato, grape, grapefruit, cranberry, apple, or orange. The granules must not be chewed, and must not be mixed with neutral pH food or drink.
Take p-aminosalicyclic acid with food to reduce gastrointestinal adverse effects.
PREPARATIONS
Oral: 4g granules per sachet (unlicensed medicine).
DRUG LEVEL MONITORING
- Drug levels need not be routinely measured.
ADVERSE EFFECTS
COMMON:
Gastrointestinal: Nausea, vomiting, diarrhoea, abdominal pain.
Immunological: Hypersensitivity reactions (5-10%) including rash & fever.
SERIOUS:
Metabolic: Hypothyroidism.
Haematological: Haemolytic anaemia (patients with G6PD deficiency), agranulocytosis, eosinophilia, leucopaenia, and thrombocytopaenia.
Hepatic: Acute hepatitis (rare).
ADVERSE EFFECTS: MONITORING
TFTs: 3 monthly (if being given in combination with prothionamide, increase to monthly)
Routine tests as per generic MDR-TB treatment monitoring guidelines.
INTERACTONS
Antacids: Fast dissolution of acid-resistant coating, resulting in early release of p-aminosalicyclic acid into the stomach. However as the stomach gastric acid will have been neutralised, degradation of p-aminosalicyclic acid to m-aminophenol will not occur. No dose adjustments required, however administration of p-aminosalicyclic acid in acidic food or drinks is not required.
Digoxin: Possible decrease in digoxin absorption. Monitor digoxin serum concentrations.
Prothionamide: increased risk of hypothyroidism, possible increased risk of hepatoxicity.
Rifamycins: reduced absorption of rifamycins. Give 8-12 hours apart.
This information is not inclusive of all drug interactions. Please discuss with a pharmacist.
CONTRA-INDICATIONS & CAUTIONS
Contraindications:
Hypersensitivity: To p-aminosalicylic acid, or to aspirin.
Renal Disease: Manufacturer advises to avoid in severe renal failure, as an inactive metabolite is renally excreted. May worsen acidosis and/or crystalluria in severe renal failure.
Cautions:
Pregnancy: Use in pregnancy has not been studied/
Breast-feeding: P-aminosalicylic acid is secreted into breast milk at 1/70th of the maternal plasma concentration.
LABORATORY INFORMATION
Please find up to date information at www.assayfinder.com regarding individual providers of drug level monitoring tests. Click on the provider to discover contact details. Turnaround time varies depending on the test and whether it is run locally or sent to an external lab. By contacting laboratories in advance, turnaround time can significantly be reduced.