MEASLES AND RUBELLA

Indications

• Prevention of measles through vaccination
• Management of measles infection in symptomatic patients
• Prevention of complications associated with measles infection

Dosage

Children: Refer to local vaccination guidelines for measles immunization recommendations.

Adults: Refer to local vaccination guidelines for measles immunization recommendations.

Mechanism of action

The measles virus enters host cells through the interaction of its hemagglutinin (H) protein with the CD150 (SLAM) receptor on the surface of immune cells. Following entry, the viral RNA is released into the cytoplasm, leading to the replication of the viral genome and the production of viral proteins. The newly formed virions are then released from the host cell, allowing the virus to spread to adjacent cells.

Pharmacodynamics

Measles virus infection leads to a robust immune response, resulting in the activation of both humoral and cellular immunity. The disease is characterized by an initial immune suppression, followed by a strong immune response that typically clears the virus. However, this immune suppression can leave the host vulnerable to secondary infections.

Pharmacokinetics

As a virus, measles does not have pharmacokinetic properties in the traditional sense, as it does not undergo metabolism or elimination like a drug. Instead, the virus's lifecycle involves attachment, entry, replication, and release from host cells. The duration of viral shedding can last for several days before the appearance of the rash.

Contra-indications

• Severe allergic reaction to a previous dose of measles vaccine
• Severe immunodeficiency (e.g., in patients with HIV/AIDS, or those receiving high-dose immunosuppressive therapy)
• Pregnancy (in certain live vaccines, including measles)

Adverse effects

• Fever
• Rash
• Diarrhea
• Otitis media
• Pneumonia
• Encephalitis (rare)

Interactions

• Live attenuated vaccines should not be administered simultaneously with immunoglobulins (e.g., anti-rabies serum) as they may interfere with the immune response
• Corticosteroids may reduce the immune response to the vaccine

Precautions

• Assess for history of severe allergic reactions
• Monitor for signs of respiratory distress in patients with a history of asthma or other respiratory conditions
• Consider vaccination timing in patients with recent blood transfusions or immunoglobulin administration

Pregnancy

Measles vaccination is contraindicated during pregnancy due to potential harm to the fetus. Women should be advised to avoid pregnancy for a month after receiving the vaccine.

Breast-feeding

Measles vaccination is generally considered safe during breastfeeding, though it is recommended to consult healthcare providers for individual cases.

Storage

Store in a refrigerator at 2°C to 8°C, do not freeze. Protect from light.

Formulations

• Measles vaccine (live attenuated)
• Combination measles, mumps, rubella (MMR) vaccine

Indications

• Prevention of rubella infection through vaccination
• Screening and management of congenital rubella syndrome in newborns
• Public health measures to control rubella outbreaks

Dosage

Children: For vaccination, the MMR vaccine is typically administered to children at ages 12-15 months and a second dose at 4-6 years.

Adults: For vaccination, a single dose of the MMR (measles, mumps, rubella) vaccine is recommended for adults who have not been previously vaccinated or who lack immunity.

Mechanism of action

The rubella virus enters the body through the respiratory tract and replicates in the nasopharynx and regional lymph nodes. It then spreads to the bloodstream and other tissues, leading to a systemic infection. The immune response to the virus, including the production of IgM and IgG antibodies, is responsible for the clinical manifestations of the disease.

Pharmacodynamics

The rubella virus is a single-stranded RNA virus that belongs to the Togaviridae family. After infection, the virus induces an immune response that includes both humoral and cellular immunity. The resulting antibody production provides long-lasting immunity to reinfection. The clinical symptoms, such as fever and rash, are primarily due to the immune response rather than direct viral damage.

Pharmacokinetics

The incubation period for rubella is typically 14 to 21 days. The virus is present in the nasopharynx and urine. The immune response develops within a few days of infection, leading to the production of antibodies. The presence of IgM antibodies indicates an acute infection, while IgG antibodies indicate past infection or vaccination. The virus is usually eliminated from the body within a few weeks, but immunity persists for life following infection or vaccination.

Contra-indications

• Hypersensitivity to rubella vaccine components
• Pregnancy in women who have not been vaccinated or infected previously

Adverse effects

• Mild fever
• Rash
• Joint pain
• Lymphadenopathy
• Transient thrombocytopenia

Interactions

• Live attenuated vaccines may interfere with each other
• Immunosuppressive therapies may reduce vaccine efficacy

Precautions

• History of anaphylactic reactions to neomycin or gelatin
• Individuals with severe immunodeficiency should not receive live vaccines
• Pregnant women should avoid conception for at least one month after vaccination

Pregnancy

Rubella vaccination is contraindicated during pregnancy due to potential harm to the fetus. Women are advised to receive the vaccine before conception.

Breast-feeding

Rubella vaccination is considered safe during breastfeeding.

Storage

Store at 2 to 8 degrees Celsius. Do not freeze. Protect from light.

Formulations

• Live attenuated rubella vaccine

Indications

• Influenza
• HIV/AIDS
• Hepatitis B and C
• Herpes simplex virus infections
• Cytomegalovirus infections
• COVID-19
• Respiratory syncytial virus infections

Dosage

Children: Refer to specific antiviral agents for dosing guidance.

Adults: Refer to specific antiviral agents for dosing guidance.

Mechanism of action

Viruses infect host cells by attaching to specific receptors on the cell surface. Once inside, they hijack the host cell's machinery to replicate their genetic material and produce viral proteins. New viral particles are assembled and released from the host cell, often destroying the cell in the process. The specific mechanism can vary depending on the virus type, including integration into the host genome in retroviruses or utilizing specific pathways for replication.

Pharmacodynamics

The pharmacodynamics of antiviral agents depend on the specific virus and the mechanism of action. Antiviral drugs may inhibit viral entry into host cells, block viral replication, or prevent the assembly of new virions. The effectiveness of antiviral therapy often relates to the stage of viral replication and the immune response of the host.

Pharmacokinetics

Pharmacokinetics of antiviral drugs varies widely based on the specific medication used. Generally, antiviral agents are absorbed through the gastrointestinal tract and distributed throughout the body. They may undergo hepatic metabolism and are often excreted through the kidneys. The half-life of these drugs can range from a few hours to several days, influencing dosing schedules.