Tadalafil information uses several different vocabularies at once. A reader may encounter pharmacokinetic terms such as AUC and half-life, mechanism terms such as PDE5 and cGMP, regimen language such as once daily and as needed, brand names such as Cialis and Adcirca, and access terms involving prescriptions, pharmacies and telehealth.
Those terms answer different questions and should not be treated as interchangeable. For example, Tmax describes when plasma concentration reaches its peak rather than when an erectile response must begin, while half-life describes drug elimination rather than a guaranteed duration of clinical effect. Likewise, tadalafil names the active drug, whereas Cialis and Adcirca identify different branded product contexts.
This glossary provides short working definitions and routes deeper questions to the canonical page that owns each topic. It is intentionally a navigation layer rather than a replacement for the detailed pharmacology, indication, safety, product or access pages.
The glossary is grouped by concept rather than forcing pharmacology, brands and pharmacy terminology into one alphabetic list. Each definition is intentionally brief, while the final column links to the page where the term is explained in depth.
Several tadalafil terms look similar while measuring different things. Following the deep-dive link is especially useful when a term affects interpretation of timing, exposure, product identity or safety.
| Term Group | What It Helps Explain | Starting Point |
|---|---|---|
| Drug and brand identity | What tadalafil is and how brands relate to the molecule | What Is Tadalafil? |
| Uses and treatment frameworks | Which conditions and regimen structures belong to tadalafil | Tadalafil Uses |
| Pharmacokinetics (PK) | What the body does to tadalafil over time | Tadalafil Pharmacokinetics |
| Pharmacodynamics (PD) | What tadalafil does to biological targets and signaling | Tadalafil Pharmacodynamics |
| Safety | Contraindications, interactions, warnings and patient factors | Tadalafil Warnings |
| Prescription and access | How prescribing, pharmacy, telehealth and cost terminology differs | Tadalafil Prescription Requirements |
The most important identity distinction is between the active drug and the finished product. Tadalafil is the established drug name, while brands and generic products are specific products that contain tadalafil within their own approved contexts.
This matters because not every tadalafil-containing product shares the same indication, dosage form or treatment framework.
| Term | Practical Definition | Deep Dive |
|---|---|---|
| Tadalafil | The established name of the active PDE5-inhibiting drug molecule used across several branded and generic products. | What Is Tadalafil? |
| Active ingredient | The pharmacologically active component of a medicine; tadalafil is the active ingredient in Cialis, Adcirca, Tadliq and corresponding tadalafil products. | Tadalafil and Cialis |
| Brand name | A proprietary product name attached to a specific finished medicine rather than the generic name of the active molecule. | Tadalafil Brand Names |
| Cialis | A branded tadalafil tablet product associated in current U.S. labeling with ED, BPH and combined ED/BPH treatment contexts. | Cialis |
| Tadalafil and Cialis | The identity relationship in which tadalafil is the active drug and Cialis is a branded product containing it. | Tadalafil and Cialis |
| Adcirca | A branded tadalafil 20 mg tablet product used in the PAH product context. | Adcirca |
| Tadalafil and Adcirca | The identity relationship in which tadalafil is the active molecule and Adcirca is a specific PAH-branded tablet product. | Tadalafil and Adcirca |
| Tadliq | A tadalafil oral-suspension product used in the PAH context rather than an ED/BPH liquid version of Cialis. | Tadliq |
| Generic tadalafil | An FDA-approved generic product containing tadalafil and referencing an appropriate brand/reference product within a defined regulatory context. | Generic Tadalafil |
| "Generic Cialis" | An informal phrase commonly used for generic tadalafil products corresponding to the Cialis-type context; generic tadalafil is the more precise term. | Generic Tadalafil |
| Manufacturer | The company responsible for manufacturing a particular finished tadalafil product; the manufacturer is not the same thing as the active ingredient. | Tadalafil Manufacturers in India |
| Product context | The combination of product identity, dosage form, indication and approved instructions surrounding a tadalafil medicine. | Tadalafil Uses |
An indication describes an approved use of a specific product; it should not be inferred from the molecule name alone. Tadalafil has ED/BPH product contexts and separate PAH product contexts, so identifying the condition is only part of identifying the treatment framework.
The terms below distinguish the principal disease and indication language used across tadalafil labeling.
| Term | Practical Definition | Deep Dive |
|---|---|---|
| Indication | A condition or clinical use included in an approved product's labeling. | Tadalafil Uses |
| ED | Erectile dysfunction: difficulty achieving or maintaining an erection sufficient for sexual activity; a labeled tadalafil use in the Cialis-type context. | Tadalafil for Erectile Dysfunction |
| BPH | Benign prostatic hyperplasia; tadalafil is labeled in the relevant tablet context for treatment of its signs and symptoms. | Tadalafil for BPH |
| ED/BPH | The separate combined indication used when erectile dysfunction and signs and symptoms of BPH coexist. | Tadalafil for ED and BPH |
| PAH | Pulmonary arterial hypertension; tadalafil is used through PAH-specific products such as Adcirca and Tadliq. | Tadalafil for Pulmonary Hypertension |
| WHO Group 1 PAH | The pulmonary arterial hypertension classification specified in current Adcirca and Tadliq labeling. | Tadalafil for Pulmonary Hypertension |
| Off-label use | Use of an approved medicine outside the specific indication or conditions described in its approved labeling; it is not the same as a labeled indication. | Tadalafil Uses |
| Treatment framework | The indication-specific structure describing how a tadalafil product is used, such as as-needed ED, daily ED/BPH or PAH treatment. | Tadalafil Dosage |
Timing language causes some of the most common tadalafil misunderstandings. A dosing schedule, pharmacokinetic peak, clinical onset and duration of response are separate concepts and should not be collapsed into one number.
The following definitions keep regimen terminology separate from PK and clinical-response terminology.
| Term | Practical Definition | Deep Dive |
|---|---|---|
| Once daily | A repeated regimen in which tadalafil is taken every day according to the applicable indication and label context. | Daily Tadalafil |
| As needed | An ED framework in which tadalafil is used in anticipation of sexual activity rather than on a fixed daily schedule. | As-Needed Tadalafil |
| Daily vs as needed | A comparison of two ED scheduling frameworks rather than two different active drugs. | Daily vs As-Needed Tadalafil |
| Dose | The amount of tadalafil administered in a particular treatment context. | Tadalafil Dosage |
| Strength | The amount of tadalafil contained in a dosage unit such as a tablet or a specified volume of suspension. | Tadalafil Strengths |
| Onset | The clinical concept of when a treatment effect may begin; it is not identical to Tmax. | Tadalafil Onset |
| Duration | How long clinically relevant response may remain possible; this is not identical to plasma half-life. | Tadalafil Duration |
| 36-hour window | The ED clinical-response context in which as-needed tadalafil demonstrated improved erectile function versus placebo at time points extending up to 36 hours after dosing; it does not mean a 36-hour erection. | Tadalafil and the 36-Hour Window |
| Sexual stimulation | The physiological trigger required for tadalafil to support the erectile-response pathway in ED; daily dosing does not remove this requirement. | Tadalafil for Erectile Dysfunction |
Pharmacokinetics, or PK, describes how tadalafil moves through the body over time. These terms describe absorption, concentration, distribution, metabolism and elimination rather than guaranteeing a particular clinical response.
PK measurements become easier to interpret when peak timing, peak concentration, total exposure and elimination are treated as separate variables.
| Term | Practical Definition | Deep Dive |
|---|---|---|
| PK / pharmacokinetics | The study of tadalafil absorption, distribution, metabolism, exposure and elimination over time. | Tadalafil Pharmacokinetics |
| Absorption | The process by which orally administered tadalafil moves from the gastrointestinal tract toward systemic circulation. | Tadalafil Absorption |
| Bioavailability | The fraction or systemic availability concept describing how much administered drug reaches systemic circulation; absolute oral tadalafil bioavailability has not been established. | Tadalafil Bioavailability |
| Tmax | The time at which the measured plasma concentration reaches its peak after a dose; it is a PK timing measure, not a guaranteed clinical-onset time. | Tadalafil Tmax |
| Cmax | The maximum measured plasma concentration reached during a concentration-time profile. | Tadalafil Cmax |
| AUC | Area under the concentration-time curve, a measure used to summarize total systemic drug exposure over a defined period. | Tadalafil AUC |
| Exposure | A broad PK concept connecting measurements such as AUC and Cmax with dose, repeat dosing, interactions and patient factors. | Tadalafil Exposure |
| Concentration-time curve | A graph or profile showing how tadalafil plasma concentration changes after dosing through absorption, peak and elimination phases. | Tadalafil Concentration-Time Curve |
| Distribution | The movement of tadalafil between blood and body tissues after systemic absorption. | Tadalafil Distribution |
| Protein binding | The reversible association of tadalafil with plasma proteins; current pharmacokinetic information places tadalafil protein binding at approximately 94%. | Tadalafil Distribution |
| Metabolism | The enzymatic conversion of tadalafil into metabolites, with CYP3A4 playing the predominant metabolic role. | Tadalafil Metabolism |
| CYP3A4 | A major drug-metabolizing enzyme responsible for much of tadalafil metabolism and an important source of drug-interaction effects on exposure. | Tadalafil and CYP3A4 |
| Clearance | A PK parameter describing the body's efficiency in eliminating tadalafil from systemic circulation. | Tadalafil Clearance |
| Half-life | The time associated with a 50% decline during a defined elimination phase; tadalafil's mean terminal half-life in healthy subjects is about 17.5 hours. | Tadalafil Half-Life |
| Dose proportionality | The relationship between changes in dose and changes in exposure measures such as AUC and Cmax. | Tadalafil Dose Proportionality |
| PK variability | Differences in tadalafil exposure between or within individuals because of metabolism, organ function, interacting drugs and other factors. | Tadalafil PK Variability |
| Food effect | The effect of meals on tadalafil absorption or exposure; standard tadalafil tablet labeling permits administration without regard to food. | Tadalafil Food Effects |
| Steady state | The repeated-dosing condition in which the overall exposure pattern becomes relatively stable from one dosing interval to the next. | Tadalafil Steady State |
| Accumulation | The increase in exposure that occurs when repeated doses overlap because tadalafil has not been completely eliminated before the next dose. | Tadalafil Accumulation |
Pharmacodynamics, or PD, describes the biological effects produced when tadalafil interacts with its targets. These terms should be kept distinct from PK: exposure describes how much drug is present, while pharmacodynamics describes what the drug does at the molecular and physiological level.
Tadalafil's central pharmacologic identity is as a PDE5 inhibitor that affects cGMP breakdown.
| Term | Practical Definition | Deep Dive |
|---|---|---|
| PD / pharmacodynamics | The study of tadalafil's molecular target, signaling effects and resulting physiological responses. | Tadalafil Pharmacodynamics |
| PDE5 | Phosphodiesterase type 5, the enzyme inhibited by tadalafil and responsible for breaking down cGMP in relevant tissues. | Tadalafil PDE5 Inhibition |
| PDE5 inhibitor | A drug class that reduces PDE5-mediated cGMP breakdown; tadalafil is one member of this class. | Tadalafil PDE5 Inhibition |
| Nitric oxide / NO | A signaling molecule involved upstream in cGMP production; tadalafil does not directly create nitric oxide. | Tadalafil and the NO-cGMP Pathway |
| cGMP | Cyclic guanosine monophosphate, a signaling molecule whose breakdown is reduced when tadalafil inhibits PDE5. | Tadalafil and the NO-cGMP Pathway |
| NO-cGMP pathway | The signaling sequence connecting nitric oxide, cGMP production, smooth-muscle effects and PDE5-mediated cGMP breakdown. | Tadalafil and the NO-cGMP Pathway |
| Smooth-muscle relaxation | A physiological effect associated with increased cGMP signaling in relevant tissues; the clinical context differs between ED, PAH and BPH. | How Tadalafil Works |
| PDE selectivity | The degree to which tadalafil inhibits PDE5 more strongly than other phosphodiesterase isoenzymes. | Tadalafil Selectivity |
| PDE6 | A phosphodiesterase involved in retinal phototransduction and commonly discussed when interpreting PDE5-inhibitor selectivity. | Tadalafil Selectivity |
| PDE11 | Another phosphodiesterase used in discussions of tadalafil's in-vitro selectivity profile; clinical consequences of PDE11 inhibition at therapeutic exposure are not established from the selectivity ratio alone. | Tadalafil Selectivity |
A dosage form, strength, brand and regulatory application are different layers of product identity. The same active molecule can appear as different finished products, and generic approval does not mean every tadalafil product shares one universal label.
These definitions help separate pharmaceutical equivalence from brand identity and indication.
| Term | Practical Definition | Deep Dive |
|---|---|---|
| Formulation | The finished dosage-form and ingredient design used to deliver tadalafil. | Tadalafil Formulations |
| Tablet | A solid oral dosage form used in Cialis, Adcirca and many generic tadalafil products. | Tadalafil Tablets |
| Oral suspension | A liquid dosage form in which tadalafil is dispersed in a vehicle; Tadliq is a U.S. PAH tadalafil oral-suspension product. | Tadalafil Oral Suspension |
| Bioequivalence | A regulatory concept used to show that a proposed generic delivers the active drug at a comparable rate and extent to its reference product. | Tadalafil Bioequivalence |
| Reference product | The approved drug product against which a generic application is compared for the relevant regulatory pathway. | Tadalafil Bioequivalence |
| FDA approval | FDA authorization of a particular product, indication or later regulatory change within a defined application context. | Tadalafil FDA Approval |
| NDA | New Drug Application, the U.S. regulatory pathway used for approval of a new drug product or product context such as Cialis, Adcirca or Tadliq. | Tadalafil FDA Approval |
| ANDA | Abbreviated New Drug Application, the FDA pathway commonly used for approval of a generic drug referencing an approved product. | Tadalafil FDA Approval |
| Generic approval | FDA approval of a specific generic application; it is not the date tadalafil itself was first approved in the United States. | Tadalafil FDA Approval |
| Expiration | The labeled period through which a properly stored product is expected to meet applicable quality specifications. | Tadalafil Expiration |
| Storage | The labeled environmental conditions for keeping a tadalafil product within its intended quality specifications. | Tadalafil Storage |
Safety terms have different regulatory and clinical meanings. A contraindication is stronger than a general interaction warning, while an adverse effect describes an unwanted event rather than a reason every patient must avoid the drug.
The definitions below provide a navigation layer only; the dedicated safety pages contain the condition-specific details.
| Term | Practical Definition | Deep Dive |
|---|---|---|
| Side effect / adverse reaction | An unwanted effect reported in association with tadalafil treatment; frequency and severity vary by study, dose and treatment context. | Tadalafil Side Effects |
| Common side effect | An adverse reaction occurring relatively frequently in clinical-study or labeling data, such as headache or dyspepsia in relevant tadalafil contexts. | Common Tadalafil Side Effects |
| Serious side effect | An adverse event with potentially important medical consequences, distinct from common expected treatment effects. | Serious Tadalafil Side Effects |
| Warning | Label information describing an important risk, precaution or circumstance requiring particular clinical attention. | Tadalafil Warnings |
| Contraindication | A circumstance in which the drug or combination should not be used under the labeled conditions because the risk is unacceptable. | Tadalafil Contraindications |
| Drug interaction | A situation in which another drug or substance changes tadalafil exposure, physiological effects or safety. | Tadalafil Drug Interactions |
| Nitrates | Nitric-oxide-donor medicines whose concomitant use with tadalafil is contraindicated because tadalafil can potentiate their blood-pressure-lowering effect. | Tadalafil and Nitrates Interaction |
| Riociguat | A soluble guanylate-cyclase stimulator that is contraindicated with tadalafil because of potentially excessive hypotensive effects. | Tadalafil and Riociguat Interaction |
| Alpha-blocker | A drug class that can lower blood pressure and has context-specific interaction considerations with tadalafil, including special BPH labeling limits. | Tadalafil and Alpha-Blockers |
| Blood-pressure effect | Tadalafil's systemic vasodilatory effect can contribute to blood-pressure lowering, particularly with other vasodilators. | Tadalafil and Blood Pressure |
| Alcohol interaction | The potential for substantial alcohol exposure to add to tadalafil-related vasodilatory or orthostatic effects. | Tadalafil and Alcohol |
| Renal impairment | Reduced kidney function that can increase tadalafil exposure or change which treatment framework is appropriate. | Tadalafil and Renal Impairment |
| Hepatic impairment | Reduced liver function that can alter the evidence base, exposure context or labeled use of tadalafil depending on severity. | Tadalafil and Hepatic Impairment |
Access terminology describes how a patient reaches a legally prescribed and dispensed tadalafil product rather than the pharmacology of the drug itself. Prescription status, telehealth, pharmacy fulfillment, delivery, insurance and discounts are separate parts of that process.
The definitions below remain intentionally neutral because product availability, coverage and prices can vary by pharmacy, provider, insurer and location.
| Term | Practical Definition | Deep Dive |
|---|---|---|
| Prescription requirement | The requirement for a valid prescription before tadalafil is dispensed in the standard U.S. prescription-drug context. | Tadalafil Prescription Requirements |
| Online prescription | A prescription obtained through a lawful remote clinical process when the applicable provider and jurisdiction permit it. | Tadalafil Online Prescription |
| Online doctor | A clinician encountered through a remote or digital care service rather than an in-person-only visit. | Tadalafil Online Doctor |
| Telehealth | Delivery of clinical evaluation or care through remote communication technologies; it is separate from pharmacy dispensing. | Tadalafil Telehealth |
| Provider | A clinician or service involved in medical evaluation and prescribing rather than the pharmacy that dispenses the drug. | Tadalafil Providers |
| Pharmacy | A licensed dispensing channel that fills a valid prescription and supplies the medication. | Tadalafil Pharmacy |
| Online pharmacy | A pharmacy service that receives and fulfills prescriptions through an online workflow; it is distinct from the clinician who determines whether a prescription is appropriate. | Tadalafil Online Pharmacy |
| Refill | A subsequent dispensing authorized under an existing prescription when refills remain available or are renewed. | Tadalafil Refill Online |
| Delivery | Shipment or local delivery of a dispensed tadalafil prescription after pharmacy processing. | Tadalafil Delivery |
| Mail order | A pharmacy-fulfillment model in which prescription medicine is shipped to the patient, often through a dedicated mail-order pharmacy. | Tadalafil Mail Order |
| Availability | Whether a particular tadalafil product, strength or formulation can currently be obtained through a given dispensing channel. | Tadalafil Availability |
| Price | The listed or transaction price associated with a tadalafil product before considering all individual insurance or discount circumstances. | Tadalafil Price |
| Cost | The amount ultimately relevant to the purchaser after variables such as pharmacy pricing, insurance and discounts are considered. | Tadalafil Cost |
| Generic price | Pricing associated specifically with generic tadalafil rather than a branded tadalafil product. | Generic Tadalafil Price |
| Discount | A coupon, pharmacy program or other pricing mechanism that may reduce out-of-pocket cost without changing the active drug. | Tadalafil Discount |
| Insurance coverage | Whether and under what conditions a health plan covers a tadalafil product or indication. | Tadalafil Insurance Coverage |
| Without insurance | A self-pay context in which tadalafil is purchased without using prescription-drug insurance coverage. | Tadalafil Without Insurance |
| Telehealth cost | The cost associated with the remote clinical service, which may be separate from pharmacy and medication costs. | Tadalafil Telehealth Cost |
| OTC | Over the counter: medicine available without a prescription under the rules of a jurisdiction; standard U.S. tadalafil remains prescription-only. | Tadalafil OTC |
Several terminology pairs sound similar but answer different questions. Keeping them separate prevents errors such as treating a PK peak as clinical onset, a long half-life as a guaranteed response duration or a brand name as the generic name of every tadalafil product.
The table below summarizes the most important distinctions.
| Terms | Key Difference | Deep Dive |
|---|---|---|
| Tmax vs onset | Tmax is the time of peak measured plasma concentration; onset describes when a clinical effect may begin. | Tadalafil Tmax / Tadalafil Onset |
| Half-life vs duration | Half-life is a PK elimination parameter; duration describes a clinical-response window. | Tadalafil Half-Life / Tadalafil Duration |
| Cmax vs AUC | Cmax describes the peak concentration; AUC summarizes total systemic exposure over time. | Tadalafil Cmax / Tadalafil AUC |
| Absorption vs bioavailability | Absorption describes entry from the administration site toward systemic circulation; bioavailability concerns systemic availability of the administered dose. | Tadalafil Absorption / Tadalafil Bioavailability |
| Steady state vs accumulation | Accumulation describes exposure building with repeated dosing; steady state describes the point at which the repeated exposure pattern stabilizes. | Tadalafil Steady State / Tadalafil Accumulation |
| PK vs PD | PK describes what the body does to tadalafil; PD describes what tadalafil does to biological targets and physiology. | Tadalafil Pharmacokinetics / Tadalafil Pharmacodynamics |
| Tadalafil vs Cialis | Tadalafil is the active drug name; Cialis is one branded tadalafil product. | Tadalafil and Cialis |
| Tadalafil vs Adcirca | Tadalafil is the active drug; Adcirca is a specific PAH-branded tadalafil product. | Tadalafil and Adcirca |
| Daily vs as needed | These are different scheduling frameworks for ED, not different tadalafil molecules. | Daily vs As-Needed Tadalafil |
| ED vs ED/BPH | ED alone and combined ED with BPH are separately defined treatment contexts. | Tadalafil for ED / Tadalafil for ED and BPH |
| PAH vs pulmonary hypertension generally | PAH is a defined subgroup; current Adcirca labeling specifically refers to WHO Group 1 PAH rather than every form of pulmonary hypertension. | Tadalafil for Pulmonary Hypertension |
| Generic drug vs brand | A generic references an approved product and meets generic-approval requirements; a brand is a proprietary finished-product identity. | Generic Tadalafil |
| Prescription vs pharmacy | A prescription authorizes dispensing after clinical evaluation; a pharmacy is the channel that fills and supplies the medicine. | Prescription Requirements / Tadalafil Pharmacy |
| Telehealth vs online pharmacy | Telehealth concerns clinical care and prescribing; an online pharmacy concerns prescription fulfillment and dispensing. | Tadalafil Telehealth / Tadalafil Online Pharmacy |
Tadalafil is the established name of the active drug molecule. It is a PDE5 inhibitor used in several branded and generic product contexts.
Tadalafil is the active ingredient, while Cialis is a specific branded tadalafil product. Every Cialis tablet contains tadalafil, but not every tadalafil product is literally Cialis.
PK means pharmacokinetics: the study of how tadalafil is absorbed, distributed, metabolized and eliminated and how plasma exposure changes over time.
PD means pharmacodynamics: the study of tadalafil's biological target, signaling effects and resulting physiological responses.
Tmax is the time at which measured tadalafil plasma concentration reaches its peak. It is a pharmacokinetic parameter and should not be treated as an exact clinical-onset time.
Cmax is the highest measured plasma tadalafil concentration during a concentration-time profile.
AUC means area under the concentration-time curve and is used to summarize total systemic drug exposure over a defined period.
No. Half-life is a pharmacokinetic elimination parameter, while duration describes a clinical-response window. They are related concepts but are not interchangeable.
PDE5 means phosphodiesterase type 5, the enzyme tadalafil inhibits. PDE5 normally breaks down cGMP in tissues where the enzyme is active.
cGMP is cyclic guanosine monophosphate, an intracellular signaling molecule. Tadalafil inhibits PDE5 and thereby reduces cGMP breakdown rather than directly creating cGMP or nitric oxide.
Once daily describes a repeated treatment schedule in which tadalafil is taken every day under the applicable indication and label framework.
As needed refers to the ED framework in which tadalafil is used in anticipation of sexual activity rather than on a regular once-daily schedule.
It refers to clinical evidence that erectile-function response with as-needed tadalafil remained demonstrable at time points extending up to 36 hours after dosing. It does not mean a continuous 36-hour erection.
ED is erectile dysfunction, BPH is benign prostatic hyperplasia, and PAH is pulmonary arterial hypertension. Tadalafil is used in each area through different indication and product frameworks.
Generic tadalafil is an FDA-approved generic product containing tadalafil that must meet the applicable generic-drug requirements for its reference product, including pharmaceutical equivalence and bioequivalence.
Bioequivalence is a regulatory comparison showing that a generic provides the active drug at a comparable rate and extent to the reference product under the study conditions.
A drug interaction describes an effect that occurs when tadalafil is combined with another drug or substance. A contraindication is a stronger labeled restriction indicating that the drug or combination should not be used under the specified circumstances.
Telehealth concerns remote clinical evaluation and prescribing, while an online pharmacy concerns dispensing and fulfillment of a valid prescription. A single service may offer both functions, but the roles are conceptually different.
No. Standard tadalafil products remain prescription medicines in the United States. Over-the-counter status in another jurisdiction should not be assumed to apply to U.S. products.
The active molecule can appear in different products with different indications, dosage forms and treatment frameworks. Tadalafil, Cialis, Adcirca and Tadliq therefore describe related but nonidentical layers of drug and product identity.