The Role of Pharmacists in Dosage Forms

Manipulation of dosage forms for patients with trouble swallowing/feeding tubes

Written by Emer Cronin, Clinical Pharmacist, University Hospital Waterford

Pharmacists are crucial decision makers in the manipulation of dosage forms for patients with swallowing difficulties. There are a wide range of patients who will require pharmacist input to alter delivery of their medication. Patient profiles can vary considerably and range from a post- stroke patient, an older adult with reduced saliva production, a woman with metastatic oesophageal cancer, a young man with an oesophageal perforation and a paediatric patient with dysphagia. As pharmacists, we advise how medicines can be manipulated safely for each of these different types of patients.

Medication comes in many different forms often allowing for different routes of administration. These routes include the oral route (tablets, capsules and liquids), rectal route (suppositories, rectal foams and enemas), nasal route (nasal sprays), transdermal route (patches), parenteral route (bolus injections, depots, infusions) inhalation (inhalers), nebulisation (nebules), buccal and sublingual route. However, deciding on the correct manipulation for a patient’s needs is not always straight forward.

In order to appropriately assess the suitability of manipulating a medication, a number of questions need to be asked. Firstly, back to pharmacy school basics, we need to know if modifying a dosage form will be safe, effective and efficient.

Safe: Could administering this modified medicine adversely affect the patient and cause harm? For example, if a medication is inappropriately crushed, its absorption profile can become erratic and subsequently cause toxicity or a complete lack of effect.

Effective: Will delivery of this drug ensure the intended therapeutic effect for the patient?

For example, if a patient with a jejunal tube receives cephalexin, the site of absorption (the duodenum) will be bypassed and so the active ingredient will not achieve therapeutic levels or have any therapeutic effect.

Efficient: Are there more appropriate and easier to administer dosage forms at hand? It is important to consider the practicality of the user involvement which may include the patient, carer or nursing staff administering the medication. Crushing tablets or opening capsules can cause aerosolization of drug powder which can pose a health risk particularly if a medication is cytotoxic or a hormonal preparation deeming it unsafe practice.

Having assessed these 3 important factors, a number of additional issues need to be addressed.

Duration: Manipulation of a medicine required for a short period of time versus a long term strategy may alter the course of action. For example, Carbamazepine suppositories are recommended for a maximum duration of 7 days due to an increased risk of rectal irritation.

Excipients: When considering switching to an alternative formulation such as a liquid, it is vital to assess the excipient content, which can include sucrose, sorbitol, sodium and ethanol that in high quantities can cause adverse effects in a patient. These adverse effects can include raised blood glucose levels, gastrointestinal disturbances, raised blood pressure, and profound drowsiness. It is also worth noting that excipients can vary across different liquid products of the same active ingredient. High osmolarity liquids will also require further dilution before administration via feeding tubes to reduce a patient’s risk of diarrhoea.

Interactions: There are many additional interactions to consider when a medication is being modified for administration, particularly via a feeding tube. For example, the high protein content of some nutritional feeds can reduce the absorption of levodopa. Drugs including phenytoin, ciprofloxacin and warfarin have significantly reduced bioavailability unless administered following a recommended 2 hour feeding break and the feed must then be stopped for a further 2 hours following administration. It is also very important to ensure medicines are never mixed when administered via feeding tubes and that each medication is flushed well.

To crush or not to crush?

It is important to be aware that crushing most medicines is an unlicensed activity and transfers liability from the manufacturer to the administrator and prescriber. Many film coated tablets are suitable for crushing which can make for a simple manipulation. Similarly, switching to a dispersible formulation when available makes for a straightforward modification. However, enteric coated or gastro-resistant tablets are generally unsuitable for crushing as doing so could increase toxicity or reduce effectiveness as well as having the potential to cause a blockage in a feeding tube. Some coated tablets may also cause taste disturbances for a patient when crushed. E.g. amiodarone tablets have a very bitter taste.

Some capsules can be opened and dispersed in water provided the enclosed granules are not enteric coated or prolonged release.

Modified release medications are not suitable for crushing and may be recognised by a number of different names: XL (extended release), SL (slow release) LA (long acting), Retard, Slo or Slow, and PR (prolonged release). However, prolonged release medication can be converted to immediate release tablets when applicable.

A drug not suitable for crushing can be switched to a drug at an equivalent dosage in the same class or can be switched to a drug in a different class with a similar therapeutic effect. E.g. Olmesartan tablets could be switched to Losartan or Lisinopril.

Calculations, Conversions and Corrections

One alternative route to the oral route is the transdermal route which will require a dose conversion. Many dose conversion calculators and tables can be sourced online e.g. opioids, Parkinson’s disease medications. It takes time for medication delivered via the transdermal route to reach steady state and sufficient therapeutic cover in this interim period needs to be ensured. It is particularly important to monitor the patient for signs of toxicity or withdrawal at this stage and to make corrections to dosages based on this.

Calculations may also need to be performed when manipulating drugs with narrow therapeutic indexes as bioavailability can vary across different formulations. For example, a dosage of 90 milligrams of phenytoin liquid is equivalent to a dosage of 100 milligrams of a phenytoin capsule.

Useful resources for information on manipulation of dosage forms include “The Handbook of Drug Administration via Enteral Feeding Tubes”, “The NEWT Guidelines” and the Summary of Product Characteristics. However, if faced with a query, it is always worthwhile contacting the pharmacist in your department who will serve as another medication expert to aid you in the minefield of the manipulation of medicines.

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