PREGSMILE TABLETS

Indications

• Insomnia
• Allergic rhinitis
• Urticaria
• Other allergic reactions

Dosage

Children: Refer to the BNF for Children for specific paediatric dosing guidance.

Adults: Refer to the BNF for specific adult dosing guidelines as it varies based on indication.

Mechanism of action

Doxylamine acts by competitively inhibiting histamine at H1 receptors, which reduces the effects of histamine in the body, leading to decreased allergy symptoms and sedation. Its substantial sedative and anticholinergic effects enhance its utility in treating sleep disturbances.

Pharmacodynamics

Doxylamine is widely recognized for its anti-allergic properties, surpassing many antihistamines in effectiveness, particularly in managing allergy symptoms and inducing sleep. It is more sedating than many prescription hypnotics and has been shown to be superior to phenobarbital in its sedative effects. Its potent anticholinergic properties further contribute to its overall therapeutic profile.

Pharmacokinetics

Doxylamine is well absorbed following oral administration. It undergoes hepatic metabolism and has a relatively long elimination half-life, which contributes to its prolonged sedative effects. The drug's pharmacokinetics may vary based on individual patient factors, including age and liver function.

Contra-indications

• Hypersensitivity to doxylamine or any component of the formulation
• Glaucoma
• Prostatic hypertrophy
• Bladder neck obstruction

Adverse effects

• Drowsiness
• Dizziness
• Dry mouth
• Constipation
• Blurred vision
• Urinary retention

Interactions

• Alcohol may enhance the sedative effects of doxylamine
• CNS depressants can increase sedation and respiratory depression
• MAO inhibitors can prolong and intensify the anticholinergic effects

Precautions

• Use with caution in patients with asthma or other respiratory conditions
• Caution in elderly patients due to increased sensitivity to anticholinergic effects
• Should not be used in patients with severe liver impairment

Pregnancy

Doxylamine is classified as category A in pregnancy; it is generally considered safe when used as directed for short-term management of nausea and vomiting in pregnancy.

Breast-feeding

Doxylamine is excreted in breast milk; caution is advised when administering to nursing mothers as it may cause sedation in the infant.

Storage

Store at room temperature, away from moisture and heat. Keep out of reach of children.

Formulations

• Tablets
• Liquid formulations

Indications

• Folate deficiency
• Megaloblastic anemia
• Prevention of neural tube defects in pregnancy
• Supplementation in patients on certain medications (e.g., methotrexate)

Dosage

Children: Refer to the BNF for Children for appropriate pa

Adults: Refer to specific guidelines or the BNF for appropriate adult dosing based on the indication.

Mechanism of action

Folate functions as a coenzyme in the conversion of homocysteine to methionine, a process that is vital for DNA synthesis and repair. It is involved in the one-carbon metabolism pathway, where it acts as a carrier of one-carbon units necessary for the synthesis of purines and thymidylate, thus supporting the production of nucleotides and DNA. This mechanism is particularly important in rapidly dividing cells.

Pharmacodynamics

Folate is critical for the formation of red blood cells and the proper functioning of the nervous system. It aids in the production of nucleic acids, which are essential for cell proliferation. Folate deficiency can lead to impaired DNA synthesis, resulting in megaloblastic anemia characterized by the presence of large, immature red blood cells in the bloodstream. Adequate folate levels are also associated with reduced risk of neural tube defects in developing fetuses.

Pharmacokinetics

Folate is absorbed in the proximal part of the small intestine, primarily in the jejunum, and is transported in the bloodstream bound to plasma proteins. It undergoes hepatic metabolism and is stored mainly in the liver. The elimination half-life varies, but dietary folate can be retained in the body for several weeks. Excess folate is excreted through the urine. The bioavailability of folate from food sources is lower compared to synthetic folic acid found in supplements.

Interactions

• folates+fluorouracil: Severe (increases risk of toxicity)
• folates+antiepileptics: Moderate (decreases concentration)
• folates+fosphenytoin: Moderate (decreases concentration)
• folates+phenobarbital: Moderate (decreases concentration)
• folates+phenytoin: Moderate (decreases concentration)
• folates+primidone: Moderate (decreases concentration)
• sulfasalazine+folates: Unknown (decreases absorption)

Pregnancy

Folate is essential for fetal development and is often recommended to prevent neural tube defects.

Breast-feeding

Folate is generally safe during breastfeeding, as it is important for both maternal and infant health.

Storage

Store in a cool, dry place, away from direct sunlight.

Formulations

• Tablets
• Injection

Indications

• Vitamin B6 deficiency
• Peripheral neuropathy
• Anemia related to B6 deficiency
• Certain neurological disorders
• Support for mood regulation

Dosage

Children: Refer to BNF for Children for appropriate dosing in paediatric patients.

Adults: Refer to specific clinical guidelines or product information for dosing recommendations.

Mechanism of action

Succinatepyridoxine acts as a coenzyme in numerous enzymatic reactions, particularly those involving amino acids. It is involved in the transamination, decarboxylation, and racemization of amino acids, which are vital processes for protein metabolism. Additionally, it plays a role in the synthesis of neurotransmitters such as serotonin, dopamine, and gamma-aminobutyric acid (GABA), which are crucial for maintaining mood and neurological function.

Pharmacodynamics

The pharmacodynamic effects of succinatepyridoxine include its ability to improve metabolic pathways related to amino acids and neurotransmitter synthesis. It enhances the body's utilization of protein, regulates mood and cognitive functions, and contributes to the synthesis of hemoglobin, which is essential for oxygen transport in the blood. Deficiency in vitamin B6 can lead to symptoms such as anemia, peripheral neuropathy, and mood disturbances.

Pharmacokinetics

Succinatepyridoxine is absorbed in the gastrointestinal tract and is widely distributed throughout the body. The liver is primarily responsible for its metabolism, converting it into its active forms, pyridoxal phosphate and pyridoxamine phosphate. These active forms are involved in various metabolic processes. The elimination half-life of the drug varies but is generally within a few hours, with renal excretion being the primary route of elimination.

Adverse effects

• Nausea
• Headache
• Dizziness
• Fatigue
• Peripheral neuropathy in high doses

Precautions

• Caution in patients with renal impairment
• Monitor for potential interactions with other medications that affect vitamin B6 metabolism

Pregnancy

Pyridoxine is generally considered safe during pregnancy, but high doses should be avoided unless prescribed.

Breast-feeding

Pyridoxine is excreted in human milk. The benefits of breastfeeding should be weighed against the need for supplementation.

Storage

Store in a cool, dry place away from light. Keep out of reach of children.

Formulations

• Tablets
• Injectable solution

Mechanism of action

Like other antihistamines, doxylamine acts by competitively inhibiting histamine at H1 receptors. It also has substantial sedative and anticholinergic effects.

Pharmacodynamics

Doxylamine is an antihistamine commonly used as a sleep aid. This drug is also used to relieve symptoms of hay fever (allergic rhinitis), hives (rash or itching), and other allergic reactions. Doxylamine is a member of the ethanolamine class of antihistamines and has anti-allergy power far superior to virtually every other antihistamine on the market, with the exception of diphenhydramine (Benadryl). It is also the most powerful over-the-counter sedative available in the United States, and more sedating than many prescription hypnotics. In a study, it was found to be superior to even the barbiturate, phenobarbital for use as a sedative. Doxylamine is also a potent anticholinergic.