Cytotoxic, steroidal or hormonal products
When considering the appropriateness of crushing medicines it is important to not only consider the safety and welfare of the patient but also that of the person administering the medicine. Hormonal medicines such as finasteride or tamoxifen, cytotoxic medicines such as methotrexate and steroidal medicines such as hydrocortisone or dexamethasone should not be crushed as this would be considered unsafe for the person crushing and administering the medicine. Crushing of these products increases the risk of the powdered drug either coming into direct contact with the person's skin causing skin sensitisation or the fine powder particles being inhaled. Allergies can also occur when other medicines are crushed such as antibiotics, where the powder either comes into contact with the skin or is inhaled. If it is deemed essential to crush a cytotoxic medicine appropriate measures must be taken to protect the person manipulating and administering the medicine.
Medicines with a narrow therapeutic index
Manipulating dosage forms can alter a product's bio-availability. The efficacy of medicines with a narrow therapeutic index can change from safe and effective to problematic and possibly dangerous with small changes in bioavailability. Digoxin has a bioavailability of about 70%, crushing the tablets could theoretically increase this to 100% giving almost a 50% increase in the effective dose.6
It would be good practice never to allow or recommend the manipulation of medicines with a narrow therapeutic index such as phenytoin, carbamazepine, digoxin, theophylline, lithium, warfarin or sodium valproate.