Tretinoin


Tretinoin, also known as all-trans retinoic acid, is medication used for the treatment of acne and acute promyelocytic leukemia. For acne, it is applied to the skin as a cream, gel or ointment. For leukemia, it is taken by mouth for up to three months.
Common side effects when used as a cream are limited to the skin and include skin redness, peeling, and sun sensitivity. When used by mouth side effects include shortness of breath, headache, numbness, depression, skin dryness, itchiness, hair loss, vomiting, muscle pains, and vision changes. Other severe side effects include high white blood cell counts and blood clots. Use during pregnancy is contraindicated due to the risk of birth defects. It is in the retinoid family of medications.
Tretinoin was patented in 1957, and approved for medical use in 1962. It is on the World Health Organization's List of Essential Medicines. Tretinoin is available as a generic medication. In 2017, it was the 293rd most commonly prescribed medication in the United States, with more than one million prescriptions.

Medical uses

Skin use

Topical tretinoin is used for the treatment of both noninflammatory and inflammatory acne. Tretinoin is most commonly used to treat acne. Multiple studies support the efficacy of topical retinoids in the treatment of acne vulgaris. It is sometimes used in conjunction with other acne treatments, as it enhances the penetration of other topical acne medications. In addition to treating active acne, retinoids accelerate the resolution of acne-induced postinflammatory hyperpigmentation. It is also useful as maintenance therapy for people who have responded to initial treatment of acne and as maintenance therapy can reduce the prolonged use of antibiotics for acne.
People with sensitive skin using the topical form should avoid using any cream or lotion that has a strong drying effect, contains alcohol, astringents, spices, lime, sulfur, resorcinol, or aspirin, as these may interact with tretinoin or exacerbate its side effects. In topical form, this drug is pregnancy category C and should not be used by pregnant women.

Leukemia

Tretinoin is used to induce remission in people with acute promyelocytic leukemia who have a mutation and who don't respond to anthracyclines or can't take that class of drug. It is not used for maintenance therapy.
By mouth, this drug is pregnancy category D and should not be used by pregnant women as it may harm the fetus.
There is some current research whether ATRA can also be used in addition to chemotherapy for patients that suffer from acute myeloid leukaemia. Therefore, Küley-Bagheri et al. conducted a Cochrane review with randomised controlled phase II and III trials in 2018 to evaluate the harms and benefits of all-trans retinoic acid in addition to chemotherapy for adults that suffer from acute myeloid leukaemia. The measured results count for patients that suffer from acute myeloid leukaemia and a high-risk myelodysplastic syndrome as this syndrome can develop into an acute myeloid leukaemia. If the participants suffered from a myelodysplastic syndrome, they were only allowed to participate in the studies if they had more than 20% of blasts. ATRA was given to participants in the intervention group in addition to chemotherapy while people were getting either an induction therapy or a consolidation therapy. Further details can be found in the original review. The review authors conducted an analysis to compare ATRA in addition to chemotherapy to chemotherapy alone: The evidence is very uncertain about the effect of ATRA in addition to chemotherapy on diarrhoea grade III/IV, nausea/vomiting grade III/IV and cardiac toxicity grade III/IV. ATRA in addition to chemotherapy probably results in little to no difference in the mortality which was measured instead of the overall survival within 24 months, the on-study mortality and the infections grade III/IV. Moreover, ATRA in addition to chemotherapy likely does not reduce the mortality, relapse and progress which was measured instead of disease- or relapse-free survival.

Photoaging

Photoaging is premature skin aging resulting from prolonged and repeated exposure to solar radiation. Features of photoaging include fine and coarse wrinkles, change in skin pigmentation, and loss of elasticity. In human skin, topical retinoids increase collagen production, induce epidermal hyperplasia, and decrease keratinocyte and melanocyte atypia. Topical tretinoin is the most extensively investigated retinoid therapy for photoaging. Topical tretinoin can be used for mild to severe photoaging in people of all skin types. Several weeks or months of use is typically required before improvement is appreciated. The benefits of topical tretinoin are lost upon discontinuation. Although it has only been studied for a duration of two years, it may be continued indefinitely. A long-term maintenance regimen with a lower concentration or less frequent application may be an alternative to continued use.

Side effects

Skin use

Topical tretinoin is only for use on skin and it should not be applied to eyes or mucosal tissues. Common side effects include skin irritation, redness, swelling, and blistering. If irritation is a problem, a decrease in the frequency of application to every other or every third night can be considered, and the frequency of application can be increased as tolerance improves. The fine skin flaking that is often seen can be gently exfoliated with a washcloth. A noncomedogenic facial moisturizer can also be applied if needed. Delaying application of the retinoid for at least 20 minutes after washing and drying the face may also be helpful. Topical retinoids are not true photosensitizing drugs, but people using topical retinoids have described symptoms of increased sun sensitivity. This is thought to be due to thinning of the stratum corneum leading to a decreased barrier against ultraviolet light exposure, as well as an enhanced sensitivity due to the presence of cutaneous irritation. The use of sun-protective clothing and/or sunscreen is recommended, particularly when prolonged sun exposure is anticipated.

Leukemia use

The oral form of the drug has boxed warnings concerning the risks of retinoic acid syndrome and leukocytosis.
Other significant side effects include a risk of thrombosis, benign intracranial hypertension in children, high lipids, and liver damage.
There are many significant side effects from this drug that include malaise, shivering, hemorrhage, infections, peripheral edema, pain, chest discomfort, edema, disseminated intravascular coagulation, weight increase, injection site reactions, anorexia, weight decrease, and myalgia.
Respiratory side effects usually signify retinoic acid syndrome, and include upper respiratory tract disorders, dyspnea, respiratory insufficiency, pleural effusion, pneumonia, rales, and expiratory wheezing, and many others at less than 10%.
Around 23% of people taking the drug have reported earache or a feeling of fullness in their ears.
Gastrointestinal disorders include bleeding, abdominal pain, diarrhea, constipation, dyspepsia, and swollen belly and many others at less than 10%.
In the cardiovascular system, side effects include arrhythmias, flushing, hypotension, hypertension, phlebitis, and cardiac failure and for 3% of patients: cardiac arrest, myocardial infarction, enlarged heart, heart murmur, ischemia, stroke, myocarditis, pericarditis, pulmonary hypertension, secondary cardiomyopathy.
In the nervous system, side effects include dizziness, paresthesias, anxiety, insomnia, depression, confusion, and many others at less than 10% frequency.
In the urinary system, side effects include chronic kidney disease and several others at less than 10% frequency.

Mechanism of action

For its use in cancer, its mechanism of action is unknown, but on a cellular level, laboratory tests show that tretinoin forces APL cells to differentiate and stops them from proliferating; in people there is evidence that it forces the primary cancerous promyelocytes to differentiate into their final form, allowing normal cells to take over the bone marrow. Recent study shows that ATRA inhibits and degrades active PIN1.
For its use in acne, tretinoin are vitamin A derivatives that act by binding to two nuclear receptor families within keratinocytes: the retinoic acid receptors and the retinoid X receptors These events contribute to the normalization of follicular keratinization and decreased cohesiveness of keratinocytes, resulting in reduced follicular occlusion and microcomedone formation. In other words, it decreases the ability of epithelial cells in hair follicles to stick together, leading to fewer blackheads and whiteheads; it also seems to make the epithelial cells divide faster, causing the blackheads to be pushed out. In addition to this direct effect of tretinoin on comedogenesis, it may also improve inflammatory acne through other mechanisms. The retinoid-receptor complex competes for coactivator proteins of AP-1, a key transcription factor involved in inflammation. Retinoids also down-regulate expression of toll-like receptor -2, which has been implicated in the inflammatory response in acne. Moreover, tretinoin and retinoids may enhance the penetration of other topical acne medications.

Biosynthesis

Tretinoin is synthesized from Beta-carotene. The Beta-carotene is firstly cleaved into Beta-carotene 15-15'-monooxygenase through site 1 double bond oxidized to epoxide. The epoxide is attacked by water to form diol in site 1. NADH, as a reduction agent, reduce the alcohol group to aldehydes.

History

Tretinoin was co-developed for its use in acne by James Fulton and Albert Kligman when they were at University of Pennsylvania in the late 1960s. The University of Pennsylvania held the patent for Retin-A, which it licensed to pharmaceutical companies.
Treatment of acute promyelocytic leukemia was first introduced at Ruijin Hospital in Shanghai by Wang Zhenyi in a 1988 clinical trial.

Etymology

The origin of the name tretinoin is uncertain, although several sources agree that it probably comes from ' + + ', which is plausible given that tretinoin is the all-trans isomer of retinoic acid. The name isotretinoin is the same root tretinoin plus the prefix . Regarding pronunciation, the following variants apply equally to both tretinoin and isotretinoin. Given that retinoic is pronounced, it is natural that is a commonly heard pronunciation. Dictionary transcriptions also include and.

Research

Tretinoin has been explored as a treatment for hair loss, potentially as a way to increase the ability of minoxidil to penetrate the scalp, but the evidence is weak and contradictory.
It has been used off-label to treat and reduce the appearance of stretch marks. It has also been studied in skin aging.