Practicing clinicians, e.g., MDs, DOs, are often visited by patients because the patient is looking for medications to help remedy their chief complaint. There are five different levels of scheduling for medications (I-V), with schedule I having the tightest controls, and V being the least restrictive. There needs to be an understanding by the physician of the mechanism and properties of the medication before prescribing, and the pharmacist must be aware of potential interactions the patient may have with their other medications.
Controlled substances are drugs considered to have the highest misuse and use disorder potential, and thus have the strictest regulation and prescription requirements on a federal and state level. To prescribe medication, a clinician must have a DEA (Drug Enforcement Administration) license; to fill a prescription, a pharmacist must also have a controlled substance license. Schedule I medications (e.g., heroin), are unable to be prescribed or filled by a pharmacist because they have no indicated medical use in the USA. Schedule II drugs are the highest level of misuse potential medications that may be prescribed by a clinician; these drugs traditionally were only allowed to be filled by paper prescription; however, they are now prescribable via electronic prescribing of controlled substances (EPCS). Schedule III-V medications may be prescribed by a clinician via traditional paper prescription, by a verbal order over the phone, or using the EPCS system. , 
The EPCS was implemented in 2010 by the DEA, which stated that clinicians might submit controlled substance prescriptions electronically; it also stated that pharmacies could dispense these electronic prescriptions. Using the EPCS from a clinician and pharmacy standpoint is voluntary, and each party may choose to use the system or not (however, some states such as New York are making the use of electronic prescribing mandatory with certain exceptions). Practitioners may still write and sign prescriptions for schedule II-V medications if they choose; verbal orders are only permitted for schedule III-V medications. The implementation of electronic prescribing has significantly reduced the number of medication errors from a prescription standpoint (legibility, dosage, frequency, etc.).
For a pharmacist to dispense a controlled substance, the prescription must include specific information to be considered valid:
There are legal limits on the number of refills and number dispended that a prescription may have. For a Schedule III-V drug, the maximum refills are 5, and the limit on quantity is 90 per allocation. Schedule II drugs have zero refills, and maximum quantity dispensed is 30 days.
Controlled substances are prescribable by a variety of clinicians: physicians, dentists, mid-level providers, podiatrists, etc. The prescribing practitioner must possess authorization from the DEA and have practicing rights within the given location of the prescription origin.
If there is any confusion for the pharmacist as to the reason for a prescription, or there are any other questions for the provider, then the pharmacist should contact the provider directly. A 2017 study showed that of prescriptions requiring clarification, 74% were new prescriptions, and only 36% of those needing clarification were electronically prescribed. The most frequent reasons for the pharmacist to contact the prescriber was for prior authorization approvals and missing prescription information. The study found that the most efficient means to correct these miscommunications was telephone contact.
It is important to remember that individual states may pass laws that alter how they govern the requirements of a prescription for different medications. An example of this is for marijuana, which at a federal level is a considered a schedule I drug, whereas some states permit its medical use and distribution. Pharmacists and practitioners should be familiar with the legislation within their practicing jurisdiction to provide the most appropriate patient care.
However, in many instances, the state law is more stringent than that of the Federal law. An example is drug monitoring systems for opioid prescriptions. Prescription drug monitoring programs are conducted on a state by state basis and are an electronic database of information on prescriptions filled within that state. The purpose of these monitoring programs is to limit drug abuse and addiction. Not all states at the time of writing this article have a fully operating monitoring program.
Partial filling of a prescription for a schedule II medication is allowed if, and only if, the pharmacist is unable to provide the patient with the full quantity prescribed; the pharmacist must make a note on the written prescription or the electronic record of how many tablets or capsules were dispensed. According to the Controlled Substance Act, the completion of a partial dispensing of schedule II medications must take place within 72 hours of the initial allocation, after which the prescription is no longer valid for the remaining undispensed quantity. If this task cannot be completed, the pharmacist should contact the practitioner about obtaining a new prescription.
Partial filling for a schedule II may also occur for patients in long-term care facilities or a patient with a terminal illness, so that the partial filling may be an individual dose; the pharmacist must document that the patient is terminally ill or in a long-term care placement before partially filling the medication. The remaining portion of the medication should be filled within 60 days from the prescription date unless the prescription is terminated because the medication is no longer necessary.
Partial filling of schedule III-V medications can be completed within six months of the original prescription.
A 2017 study found that there was a significant reduction in prescription errors for patients discharged from emergency departments when medications were prescribed electronically versus handwritten. The specific findings were that electronic prescriptions demonstrated decreased incidence of missed dosages, inaccurate frequency of medication, incorrect dosage strength, and the overall ability to read to the document (e.g., some clinician handwriting was illegible).
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