Guideline for the Stability Testing of Nonprescription (OTC) Drug Products Not Regulated by an NDA/ANDA

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Voluntary Codes and Guidelines |

June 24, 2009
June 26, 2012


Prior to this guideline, the nonprescription industry did not have directly applicable stability testing guidance for over-the-counter (OTC) monograph drug products not regulated by an NDA/ANDA. Historically, nonprescription drug companies developed their stability testing programs based upon their best interpretation and practical application of the most current FDA and/or ICH guidance for new drug products. Because of the unique requirements associated with new drug products, the direct application of the FDA and ICH guidance is sometimes inappropriate and impractical. Drug products with an OTC monograph will typically be well characterized with a significant body of information, a well-known safety profile, and a long history of use in multiple dosage forms. For this reason, the OTC industry is proposing this guideline for OTC drug products not regulated by an NDA/ANDA. For simplicity, OTC drug products not regulated by an NDA/ANDA will be referred to as OTC monograph drug products.

Objectives of the Guideline

To define the minimum stability data package to support the commercial distribution of OTC monograph drug products in the United States per climatic zone II. The stability data package will be based on development stability studies. These studies will be used to establish the tentative expiration dating period and label storage statement for the OTC monograph drug product.

This guideline recognizes that a significant body of scientific information may exist for OTC drug products. Alternative approaches may be used when there are scientifically justifiable reasons.

Scope of the Guideline

This guideline applies specifically to OTC monograph drug product stability. This guideline does not currently seek to cover the stability testing of:

  • Nonprescription drug products regulated by an NDA/ANDA
  • Drug substances
  • Drug products used in clinical trials
  • Marketed product stability

Additionally, this guideline is not applicable to:

  • Specific details of the sampling and testing for particular dosage forms in their proposed container closures
  • Safety studies

General Principles

The purpose of product stability testing is to provide evidence on how the quality of a drug product in a specific package configuration varies with time under the influence of a variety of environmental factors such as temperature, humidity, and light, and to establish a shelf-life period for the drug product and recommended storage conditions.

The choice of test conditions defined in this guideline is based on an analysis of the effects of climatic conditions only in the United States.

The design of the stability studies for the OTC monograph drug product should be based on knowledge of the behavior and properties of the drug substance and drug products that use the same active ingredient(s), manufacturing process, quantity of excipients, and container/closure system. The likely changes on storage and the rationale for the selection of attributes to be tested in the formal stability studies should be stated.

Photostability Testing

Stability data should be available to demonstrate that the drug product is not susceptible to light. At least one batch of the drug product packaged in the container closure proposed for market should be tested for photostability effects. This testing may be omitted, if a scientific justification can be provided to show that the drug product in the container closure proposed for market will not be susceptible to photostability effects.

The irradiation of the packaged drug product is to be conducted according to the ICH Q1B guidance for photostability testing of drug products. Generally, not all test parameters are required in order to assess photostability effects. Scientific judgment should be used in order to determine the appropriate subset of parameters required for the photostability assessment.

Selection of Batches

Stability data should be available on at least one primary batch of the drug product. Additional primary batches may be necessary for new product formulations and instances where no similar formulations exist. The primary batch(es) should be of the same formulation and packaged in the same container closure system as proposed for marketing. The manufacturing process used for primary batch(es) should simulate that to be applied to production batches and should provide product of the same quality and meeting the same specification as that intended for marketing. The batch(es) should be at least pilot scale (1/10 Production Scale); a scientific rationale may be used to justify a smaller batch size. Where practical, if multiple batches are studied, the drug product should be manufactured using different batches of the drug substance. Stability studies should be performed on each individual strength, container size, or other attribute unless a reduced sampling and testing program can be scientifically justified (e.g. bracketing and/or matrixing approaches can be used).

Container/Closure System

Stability testing should be conducted on the dosage form packaged in the container closure system proposed for marketing.


A specification is composed of a list of tests with references to analytical procedures and the proposed acceptance criteria. The acceptance criteria can be numerical limits or ranges, textual descriptions, or other requirements depending on the type of test specified.

The list of tests should include an assessment for all of the drug product attributes that are susceptible to change during storage and that are likely to influence quality, safety, and/or efficacy. The testing should cover, as appropriate, the physical, chemical, biological, and microbiological attributes. Analytical test procedures should be fully validated and stability indicating. There are some test methodologies where it may not be necessary or appropriate, using good scientific judgment, to validate a test procedure (e.g., tablet hardness, where a calibrated test instrument is used).

Acceptance criteria for shelf-life specifications should be based on all of the available stability information and compendial requirements. Specifications for product release may be more restrictive than shelf-life specifications in order to account for changes observed during storage of stability samples.

For multi-dose liquid and semi-solid drug products, antimicrobial preservative effectiveness testing (AET) should be demonstrated in the multi-dose container(s). If differences between the release and shelf-life acceptance criteria for AET are necessary, the difference should be scientifically justified based on a correlation between preservative content and preservative effectiveness.

Testing Frequency

The frequency of testing, for the primary stability studies, should be designed in order to adequately determine the stability profile for the drug product. This testing frequency will typically be 0, 3, 6, 9, 12, 18, 24 months and annually thereafter through the proposed shelf-life. Justification for doing less than these time points should be provided.

At the accelerated storage condition, a minimum of three time points are recommended to be tested over a three month period (including the initial and final time; e.g. 0, 1, and 3 months). When the drug product fails to meet the established shelf-life criteria at the accelerated storage condition (such as 40C/75%RH), intermediate accelerated conditions may be used to insure that at minimum, some acceptable accelerated data is available to show that the product can withstand the typical excursions experienced in the distribution chain once the product is marketed. In addition, a drug product that fails to meet shelf-life specifications for accelerated conditions will require additional data from long term and/or intermediate accelerated conditions in order to establish an acceptable tentative expiration dating period for market.

Storage Conditions

In general, a drug product should be evaluated under storage conditions (with appropriate tolerances) that test its thermal stability and, if applicable, its sensitivity to moisture or potential for solvent loss. The storage conditions and the lengths of studies chosen should be sufficient to cover storage, shipment, and subsequent use.

Long term and accelerated storage conditions for drug products are detailed in the sections below. The general case applies if the drug product is not specifically covered by a subsequent section. Alternative storage conditions can be used, if justified.

Container orientation should be considered when designing stability study protocols for liquid and semi-solid products.

Storage Conditions – General Case


Storage Condition

Long Term

25 ± 2°C / 60 ± 5% RH


30 ± 2°C / 65 ± 5% RH


40 ± 2°C / 75 ± 5% RH


If at the accelerated storage condition the drug product fails to meet the established shelf-life criteria, alternative accelerated conditions may be used to insure that at minimum, some acceptable accelerated data is available to show that the product can withstand the typical excursions experienced in the distribution chain once the product is marketed.

Storage Conditions – Drug Products Packaged in Impermeable Containers

Sensitivity to moisture or potential for solvent loss is not a concern for drug products packaged in impermeable containers that provide a permanent barrier to passage of moisture or solvent. Thus, stability studies for products stored in impermeable containers can be conducted under any controlled or ambient humidity condition.

Storage Conditions – Drug Products Packaged in Semi-Permeable Containers

Aqueous-based based (those containing ≥ 50% water) products packaged in semi-permeable containers should be evaluated for potential water loss in addition to physical, chemical, biological, and microbiological stability. This evaluation can be carried out under conditions of low relative humidity, as discussed below. Ultimately, it should be demonstrated that aqueous-based drug products stored in semi-permeable containers can withstand low relative humidity environments. Other comparable approaches can be developed and reported for non-aqueous, solvent-based products.


Storage Condition

Long Term

25 ± 2°C / 40 ± 5% RH


30 ± 2°C / 65 ± 5% RH


40 ± 2°C / NMT 25% RH


A 5% loss in water from the initial value is recommended to be the limit of acceptability for a product packaged in a semi-permeable container after an equivalent of 3 months’ storage at 40°C/NMT 25% RH. However, for small containers (1 mL or less) or unit-dose products, a water loss of 5% or more after an equivalent of 3 months’ storage at 40°C/NMT 25% RH may be appropriate, if justified.

An alternative approach to studying at the reference relative humidity as recommended in the table above (for either long term or accelerated testing) is performing the stability studies under higher relative humidity and deriving the water loss at the reference relative humidity through calculation. This can be achieved by experimentally determining the permeation coefficient for the container closure system or, as shown in the example below, using the calculated ratio of water loss rates between the two humidity conditions at the same temperature. The permeation coefficient for a container closure system can be experimentally determined by using the worst case scenario (e.g., the most diluted of a series of concentrations) for the proposed drug product.

Example of an approach for determining water loss:

For a product in a given container closure system, container size, and fill, an appropriate approach for deriving the water loss rate at the reference relative humidity is to multiply the water loss rate measured at an alternative relative humidity at the same temperature by a water loss rate ratio shown in the table below. A linear water loss rate at the alternative relative humidity over the storage period should be demonstrated. For example, at a given temperature, e.g., 40°C, the calculated water loss rate during storage at NMT 25% RH is the water loss rate measured at 75% RH multiplied by 3.0, the corresponding water loss rate ratio.

Alternative Relative Humidity

Reference Relative Humidity

Ratio of water loss rates at a given temperature

60% RH

25% RH


60% RH

40% RH


65% RH

35% RH


75% RH

25% RH



Valid water loss rate ratios at relative humidity conditions other than those shown in the table above can also be used.

Storage Conditions – Special Case

Drug products intended for storage in a refrigerator, freezer, below -20°C, or under other conditions should be treated on a case-by-case basis.

Post-Launch Stability Requirements

Post-launch marketed product stability testing will be conducted to confirm the assigned expiration dating period as required by the current Good Manufacturing Practices (cGMPs).


A scientific approach should be adopted in the presentation and evaluation of stability information for establishing a tentative expiry period. Results from research and development batches on similar or closely related formulations, on similar or closely related marketed products, and data published in the literature, as well as results from the specific stability study may be considered a body of knowledge that can be used in the scientific assessment. Results from physical, chemical and microbiological tests as appropriate for the dosage form should be included in this evaluation.

The purpose of the accelerated stability study is to establish, based on testing a minimum of one batch of the drug product, a tentative expiry period and label storage instructions applicable to all future batches of the drug product manufactured and packaged under similar circumstances.

When the data from an accelerated stability study remains within established limits, while maintaining potency, a tentative expiry period can be assigned prior to marketing the product. A twenty-four month expiry period may be assigned upon successful completion of three months accelerated testing. For those products that cannot tolerate 40C accelerated testing, stability data at the intermediate condition may be used to support a tentative expiry period of twenty-four months. Using sound scientific judgment, shorter expiry periods may be assigned based on less than three months of accelerated testing and longer tentative expiry periods may be justified using extended periods of accelerated testing or a combination of long term and accelerated testing. Any longer tentative expiry period or extension of an expiration dating period should be made based on scientific justification, historical data on same/similar formulas/products, and calculations using the Arrhenius equation (all with appropriate documentation).

When the data clearly exhibits no change or stability trend over time, a formal statistical analysis is not necessary.

An approach for analyzing data of a quantitative attribute that is expected to change with time is to determine the time at which the 95% one-sided confidence limit for the mean intersects the acceptance criterion. If analysis shows that the batch-to-batch or among package configuration variability is small, it is advantageous to combine the data into one overall estimate. This can be done by first applying appropriate statistical tests (e.g., p values for level of significance of rejection of more than 0.25) to the slopes of the regression lines and zero time intercepts for the individual batches or package configurations. If it is inappropriate to combine data from several batches, the overall shelf life should be based on the minimum time a batch can be expected to remain within acceptance. If it is inappropriate to combine data from several package configurations, then each configuration should be evaluated separately with an expiry period being assigned to the individual package configuration rather than to the product as a whole.


A storage statement should be established for the labeling in accordance with current FDA or USP requirements. The statement should be based on the stability evaluation of the drug product. Where applicable, specific instructions should be provided, particularly for drug products which require special storage conditions.


The following definitions are provided to facilitate interpretation of the guideline.

Accelerated testing
Studies designed to increase the rate of chemical or physical change of a drug product by using exaggerated storage conditions as part of the formal stability studies. Data from these studies, in addition to long term stability studies, can be used to assess longer term chemical effects at non-accelerated conditions and to evaluate the effect of short term excursions outside the label storage conditions such as might occur during shipping. However, results from accelerated studies are not always representative of similar results from the long-term label storage studies.

The design of a stability schedule such that only samples on the extremes of certain design factors, e.g., strength, package size, are tested at all-time points as in a full design. The design assumes that the stability of any intermediate levels is represented by the stability of the extremes tested. Where a range of strengths is to be tested, bracketing is applicable if the strengths are identical or very closely related in composition (e.g., for a tablet range made with different compression weights of a similar basic granulation, or a capsule range made by filling different plug fill weights of the same basic composition into different size capsule shells). Bracketing can be applied to different container sizes or different fills in the same container closure system.

Container/Closure system
The sum of packaging components that together contain and protect the dosage form. This includes primary packaging components and secondary packaging components, if the latter are intended to provide additional protection to the drug product. A packaging system is equivalent to a container closure system.

Development studies
Stability studies initiated during the development of a drug product. If these studies are to be used for the purpose of assigning a tentative expiration dating period, they are sometimes called “formal” stability studies.

Dosage form
A pharmaceutical product type (e.g., tablet, capsule, solution, cream) that contains a drug substance generally, but not necessarily, in association with excipients.

Drug product
The dosage form in the final immediate packaging intended for marketing.

Drug Substance
The unformulated active pharmaceutical ingredient that may subsequently be formulated with excipients to produce the dosage form.

Anything other than the drug substance in the dosage form.

Expiration date
The date placed on the container label of a drug product designating the time prior to which a batch of the product is expected to remain within the approved shelf life specification if stored under defined conditions, and after which it must not be used.

Formal stability studies
Stability studies initiated during the development of a drug product in a specific package according to a prescribed stability protocol in order to establish or confirm the shelf life or expiration dating period for the product.

Impermeable containers
Containers that provide a permanent barrier to the passage of gases or solvents, e.g., sealed aluminum tubes for semi-solids, sealed glass ampoules for solutions.

Long term testing
Stability testing of samples that have been stored at the proposed (or approved) labeled storage condition for a drug product in a specific package. Samples are stored and tested through the entire shelf life period.

The design of a stability schedule such that a selected subset of the total number of possible samples for all factor combinations is tested at a specified time point. At a subsequent time point, another subset of samples for all factor combinations is tested. The design assumes that the stability of each subset of samples tested represents the stability of all samples at a given time point. The differences in the samples for the same drug product should be identified as, for example, covering different batches, different strengths, different sizes of the same container closure system, and, possibly in some cases, different container closure systems.

Pilot scale batch
A batch of a drug product manufactured by a procedure fully representative of and simulating that to be applied to a full production scale batch. For solid oral dosage forms, a pilot scale is generally, at a minimum, one-tenth that of a full production scale or 100,000 tablets or capsules, whichever is the larger.

Primary batch
A batch of a drug product used in a formal stability study for the purpose of establishing an expiration dating period. A primary batch of a drug product should be at least a pilot scale batch; a scientific rationale may be used to justify the use of a smaller batch.

Production batch
A batch of drug product manufactured at production scale using production equipment in a production facility.

Semi-permeable containers
Containers that allow the passage of solvent, usually water, while preventing solute loss. The mechanism for solvent transport occurs by absorption into one container surface, diffusion through the bulk of the container material, and desorption from the other surface. Transport is driven by a partial-pressure gradient.

Shelf life (also referred to as expiration dating period)
The time period during which a drug product is expected to remain within the approved shelf life specification, provided that it is stored under the conditions defined on the container label.

Specification – Release
The combination of physical, chemical, biological, and microbiological tests and acceptance criteria that determine the suitability of a drug product at the time of its release.

Specification – Shelf life
The combination of physical, chemical, biological, and microbiological tests and acceptance criteria that determine the suitability of a drug product throughout its shelf life.

Storage condition tolerances
The acceptable variations in temperature and relative humidity of storage facilities for formal stability studies. The equipment should be capable of controlling the storage condition within the ranges defined in this guideline. The actual temperature and humidity (when controlled) should be monitored during stability storage. Short term spikes due to opening of doors of the storage facility are accepted as unavoidable. The effect of excursions due to equipment failure should be addressed, and reported if judged to affect stability results. Excursions that exceed the defined tolerances for more than 24 hours should be described in the study report and their effect assessed.

Supporting data
Data, other than those from formal stability studies, that support the analytical procedures, the proposed shelf life, and the label storage statements. Such data include (1) stability data on small scale batches of materials, investigational formulations not proposed for marketing, related formulations, and product presented in containers and closures other than those proposed for marketing; (2) information regarding test results on containers; and (3) other scientific rationales.

Tentative Expiry Period
A shelf-life for a drug product in a specific package that has been established using either accelerated or less than full term stability data. A tentative expiry period becomes a shelf-life period once acceptable long term stability data are available to confirm the tentative period.


ICH Q1A “Stability Testing of New Drug Substances and Drug Products”

ICH Q1B “Photostability Testing of New Drug Substances and Products”

ITG-41 (FDA) “Expiration Dating and Stability Testing for Human Drug Products”