Scientists do not know exactly what causes psoriasis, but they believe it happens when the immune system attacks healthy cells, causing skin cells to grown too fast.
Psoriasis is a chronic condition. There is currently no cure, but treatment can help control symptoms, and newer treatments are proving more effective than previous ones for some types of psoriasis.
People have traditionally used over-the-counter therapies, lifestyle remedies, and some prescription drugs to treat psoriasis, but doctors may now prescribe injectable drugs known as biologics for some types when symptoms are moderate to severe.
In recent years, the Food and Drug Administration (FDA) have approved a number of new drugs, and there is hope that these can significantly improve the quality of life for people with psoriasis.
As with all medications, some side effects are possible. A doctor will discuss these with the individual before prescribing a drug.
Some injectable drugs may help reduce the symptoms and progression of psoriasis.
Most of the injectable medications for treating psoriasis are known as biologic drugs, or "biologics."
These drugs target the immune system. Different biologics work in different ways, but they all target cytokines, a type of protein that the immune system produces.
In normal circumstances, cytokines play a role in protecting the body from harmful or unwanted substances. When the body produces extra cytokines as part of the immune response, inflammation occurs. Normally this passes, but in some cases, such as psoriasis, the immune response persists and the inflammation continues.
Scientists make biologics from living cells that they grow in a laboratory. They harvest special types of proteins from these cells and use these proteins in medications. These medications aim to resolve the symptoms of psoriasis by reducing the extra immune activity that psoriasis involves.
The FDA have approved several medications to treat psoriasis.
Some of these medicines can target special T-cells in the immune system. Others can stop proteins in the immune system from growing.
Doctors only usually prescribe these medicines when a person's psoriasis is moderate to severe, and when other treatments have not worked.
Interleukin-12 and -23
Interleukin-12 (IL-12) and interleukin-23 (IL-23) are two of the proteins that the body produces as part of the immune response. They are linked to psoriasis symptoms. Blocking the actions of these proteins may reduce psoriasis inflammation.
Ustekinumab (stelara) is an IL-12 blocker that has FDA approval to treat various types of psoriasis. It binds to both IL-12 and IL-23 and reduces their impact in the body.
The FDA have also approved the following IL-23 blockers to treat plaque and other types of psoriasis:
- Guselkumab (Tremfya)
- Tildrakizumab (Ilumya)
- Risankizumab (Skyrizi)
Risankizumab is currently awaiting FDA approval.
IL-17A is another protein that appears to trigger an immune system reaction that can lead to psoriasis. Blocking this action may also prevent this reaction.
Examples of FDA-approved psoriasis injections that block IL-17A include:
- secukinumab (Cosentyx)
- ixekizumab (Taltz)
- brodalumab (Siliq)
Tumor necrosis factor-alpha blockers
Proteins known as cytokines can trigger inflammation in the body. Tumor necrosis factor-alpha (TNF-alpha) is one type of cytokine.
When a person has a condition such as rheumatoid arthritis or psoriasis, the body produces too much TNF-alpha. Blocking TNF-alpha production should, in theory, prevent certain psoriasis symptoms.
The FDA have approved the following TNF-alpha blockers to treat psoriasis:
- adalimumab (Humira)
- certolizumab pegol (Cimzia)
- etanercept (Enbrel)
- golimumab (Simponi)
- infliximab (Remicade)
A doctor will deliver Remicade using an intravenous (IV) infusion instead of a standard injection.
The doctor should speak to the individual about the drugs available, how to use them, and the possible side effects. They will choose a drug that is appropriate for the type of psoriasis the person has.
They should also monitor the person to check for any unwanted effects, and they may suggest an alternative if one option appears to be unsuitable.
A doctor may prescribe another medication — methotrexate (Trexall, Rheumatrex) — to treat psoriasis. Methotrexate is a systemic drug. This means it works throughout the body — as do the biologics — but it is not a biologic.
Instead it is a disease-modifying anti-rheumatic drug, or DMARD. It works to suppress the immune system, but it does this in a different way from the biologics.
A doctor may prescribe this drug alongside a biologic or another treatment. Each combination needs FDA approval, because combining certain drugs can increase the risk of adverse effects.
Methotrexate is available either as an oral medicine in pill form or as an injection.
Methotrexate can have some side effects. Drugs that reduce the action of the immune system can increase the risk of infections. Studies have shown that combining methotrexate with other drugs may increase this risk.
Originally, doctors prescribed methotrexate in larger dosages as a chemotherapy agent to treat cancer. Now, they use it to treat a number of health conditions, including psoriasis and rheumatoid arthritis.
Benefits and drawbacks
Injectable drugs are proving effective in improving the symptoms of moderate to severe symptoms of psoriasis.
The frequency with which a person needs an injection can vary from twice a week to once every 3 months.
For some of these treatments, the person will need to go to the doctor's office each time. For others, they can learn how to use it at home.
Seeing the doctor regularly for an injection may be disruptive, but it also enables the doctor to monitor symptoms and check for any adverse reactions to the drug.
A person should speak to their doctor if they notice any adverse effects.
Drugs that impact the immune system can have serious side effects.
They may leave a person more prone to infections, such as tuberculosis (TB).
A doctor will screen an individual for TB before and during treatment.
The effect of biologic drugs on pregnancy remain unclear. For this reason, doctors rarely prescribe them for women who are pregnant or nursing.
Side effects related to psoriasis injections can range from mild to severe.
Adverse effects of biologic drugs
More common side effects include:
- a higher risk for respiratory or urinary tract infections
- flu-like symptoms, such as low energy and body aches
- reactions at the injection site, such as redness, swelling, or discomfort
Rarer side effects include:
- blood disorders
- a higher risk of certain cancer types
- an increased risk of serious nervous system disorders, including multiple sclerosis (MS), nervous system inflammation, and seizures
Adverse effects of methotrexate
Methotrexate is not a biologic drug, and it has different side effects. The most common ones are:
- appetite loss
Long-term methotrexate treatment can lead to:
- liver damage
- changes to red and white blood cell production
A doctor should inform a person who is receiving psoriasis injections about the possible side effects and their symptoms. Anyone who experiences new or worsening symptoms after taking a drug should contact their doctor.
Other treatment options
There are several different types of psoriasis, and they may need different approaches.
When prescribing a treatment a doctor will consider:
- the psoriasis type
- where the symptoms are
- how severe the symptoms are
Many people use topical treatments to remedy the external symptoms of psoriasis.
Topical corticosteroids can reduce inflammation in the skin in cases of mild to moderate psoriasis.
Other treatments include:
- oral and topical vitamin D analogues
- anthralin (Dritho-Scalp)
- calcineurin inhibitors, such as tacrolimus (Prograf)
- salicylic acid
- coal tar
- topical retinoids, such as tazarotene (Tazorac, Avage)
Moisturizers that are suitable for people with psoriasis are available for purchase online.
Additional medication options
Other oral treatments include oral corticosteroids, retinoids, and cyclosporine.
Oral corticosteroids are a systemic therapy that can improve symptoms throughout the body. Steroid treatment can have adverse effects. These may include rebound psoriasis or a triggering of a more severe form of the disease, but how these impact a person with psoriasis remains unclear, according to a study published in 2012.
Apremilast (Otezla) is a DMARD that may reduce the incidence of psoriasis plaques. People can take it by mouth. In 2017, the authors of a review described it as "well tolerated." The user does not need ongoing lab tests to monitor for adverse effects.
Apremilast is a phosphodiesterase 4 (PDE4) inhibitor. Research has found links between PDE4 and the inflammation that leads to psoriasis, so taking a PDE4 inhibitor may help to reduce the incidence of psoriasis plaques.
Light therapies may help. These involve exposing the skin to a certain amount of ultraviolet (UV) light, usually in a doctor's office.
Excess exposure to UV light can increase the risk of skin cancer. At least one study has concluded that sun exposure may benefit a person with psoriasis, but they need to approach this slowly and carefully because too much sun can make symptoms worse.
People who live in an area with little sun exposure should ask their doctor about using an artificial light source, such as a light box.
A controlled amount of sun exposure may help reduce symptoms.
Psoriasis is an inflammatory skin condition. Some lifestyle choices can trigger inflammation, and they may worsen the symptoms of psoriasis.
- intense or prolonged sun exposure
These factors may not trigger symptoms in everyone with psoriasis, but if a person cuts them out, they may find their symptoms improve.
Alcohol may affect how well psoriasis medicines work, so avoiding alcohol may help some people.
Bathing with lukewarm water may help, especialy if the person adds one of the following to the water:
- unscented bath oil
- colloidal oatmeal
- Dead Sea salts
- Epsom salts
Applying moisturizers to the skin after taking a bath may also be beneficial.
When to see a doctor
Anyone who is receiving injectable psoriasis medication should contact their doctor if they experience signs of an infection. These may worsen quickly and be harder to treat if the person's medication is targeting their immune system.
Symptoms of an infection include:
- flu-like symptoms
- sores that do not heal
The person should also see their doctor if they notice other symptoms or side effects of a medication, or if their symptoms worsen. Sometimes, a biologic becomes less effective after a while. The doctor may need to adjust the dose or suggest a different medication.
Biologic and other injectable drugs can be effective in treating severe to moderate psoriasis, although sometimes there may be side effects.
A person should discuss their medication with their doctor and inform the physician if there are any changes or concerns.