Slow-release (SR) capsules are a commonly prepared compounded dosage form in which the drug is intended to release over a period of time. Unlike manufactured extended-release capsules, compounded slow-release capsules do not have an exact time of release. Therefore, it is important if converting a patient from an extended-release capsule to a compounded SR capsule, to make both the prescriber and patient aware of possible initial serum fluctuations and monitor the patient accordingly.
SR compounded capsules are made by the addition of a pre-determined amount of Hydroxypropyl methylcellulose (4000 mPa.s) or Hypromellose (4000 mPa.s),alongside another filler, like Microcrystalline Cellulose, which comprises the remaining amount of total filler needed.
General guidelines for the amount of Hypromellose (4000 mPa.s) required to compound SR capsule depends on the solubility of the API and/or it’s Biopharmaceutics Classification System (BCS):
- If the API is solubleand/or has a BCS Class I or Class III, Hypromellose (4000 mPa.s) should be added at 40% of the capsule fill volume.
- If the API is not soluble and/or has a BCS ClassII or IV, Hypromellose (4000 mPa.s) should be added at 35% of the capsule fill volume.
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Radojkovic, B., Milic, J., & Calija, B. (2012). Compounding of slow-release Niacinamide capsules: Feasibility and Characterization. International Journal of Pharmaceutical Compounding, 16(5), 434-437
Vu, N., Kupiec, T., & Raj, V. (2009).Compounding Slow-Release Pharmaceuticals. International Journal Of Pharmaceutical Compounding, 13(2), 144-145.
Zur, E. "Compounding slow-release capsules: a comprehensive review and an Excel spreadsheet for faster calculations of excipients." International journal of pharmaceutical compounding 17.1 (2013): 10-22.