Entakon M

Entakon M Uses, Dosage, Side Effects, Food Interaction and all others data.

Metronidazole, a nitroimidazole has an extremely broad spectrum antiprotozoal and antimicrobial activities, with high activity against anaerobic bacteria and protozoa. Metronidazole is usually completely and rapidly absorbed after oral administration. The half-life in plasma is about 8 hours. About 10% of the drug is bound to plasma proteins. Metronidazole penetrates well into body tissues and fluids. The liver is the main site of metabolism. Both unchanged Metronidazole and metabolites are excreted in various proportions in the urine after oral administration.

Metronidazole treats amebiasis, trichomoniasis, and giardiasis, exerting both antibacterial and antiprotozoal activities. Metronidazole is an effective treatment for some anaerobic bacterial infections. Metronidazole has shown antibacterial activity against the majority of obligate anaerobes, however, during in vitro studies, it does not demonstrate significant action against facultative anaerobes or obligate aerobes. The nitro group reduction of metronidazole by anaerobic organisms is likely responsible for the drug's antimicrobial cytotoxic effects, causing DNA strand damage to microbes.

A note on convulsions and neuropathy and carcinogenesis

It is important to be aware of the risk of peripheral neuropathy and convulsions associated with metronidazole, especially at higher doses. If convulsions or numbness of an extremity occur, discontinue the drug immediately. Metronidazole has been found to be carcinogenic in mice and rats. The relevance to this effect in humans is unknown. It is advisable to only administer metronidazole when clinically necessary and only for its approved indications.

Tetracycline has its main mechanism of action on protein synthesis, and an energy-dependent active transport system pumps the drug through the inner cytoplasmic membrane of bacteria. Once inside the bacterial cell, Tetracycline binds specifically to the 30s ribosomes and inhibit bacterial protein synthesis.

Many Gram positive aerobic Cocci are susceptible, but many strains of staphylococci, streptococci and even some pneumococci are resistant to Tetracycline. Thus, tetracycline is not the drug of choice in infections due to gram positive aerobes.

Pseudomonas and many Enterobacteriaceae are resistant. Urinary concentrations are adequate for some community - acquired E. coli and consequently, Tetracycline is still used in uncomplicated initial UTIs. Tetracycline is also active against and is the drug of choice for Brucella species, Calymmatobacterium granulomatis, Vibrio cholerae and V. vulnificus.

Tetracycline is also active against anaerobic species of bacteria and since concentrations of the drug are quite high in the gastrointestinal contents, the enteric flora are usually altered by the drug.

Tetracycline is incompletely absorbed from the gastro-intestinal tract, about 60 to 80% of a dose of tetracycline usually being available. It is widely distributed through the body tissues and fluids.

Tetracycline has a half-life of about 12 hours. It is excreted in the urine and in the faeces.

Tetracycline exhibits its bacteriostatic action by reversibly binding to the 30S subunits of the ribosome, thus preventing protein synthesis and arresting cell growth. It has a broad spectrum of antimicrobial activity including Chlamydiaceae, Mycoplasma spp., Rickettsia spp., spirochaetes, many aerobic and anaerobic gm+ve and gm-ve pathogenic bacteria and some protozoa.

Tetracycline is a short-acting antibiotic that inhibits bacterial growth by inhibiting translation. It binds to the 30S ribosomal subunit and prevents the amino-acyl tRNA from binding to the A site of the ribosome. It also binds to some extent to the 50S ribosomal subunit. This binding is reversible in nature. Additionally tetracycline may alter the cytoplasmic membrane of bacteria causing leakage of intracellular contents, such as nucleotides, from the cell.

Entakon M
Uses
Dosage
Side Effect
Precautions
Interactions
Uses during Pregnancy
Uses during Breastfeeding
Accute Overdose
Food Interaction
Half Life
Volume of Distribution
Clearance
Interaction With other Medicine
Contradiction
Storage

Trade Name	Entakon M
Generic	Tetracycline + Metronidazole
Weight	333mg
Type	Capsule
Therapeutic Class
Manufacturer	Kontest Chemicals Ltd
Available Country	India
Last Updated:	September 19, 2023 at 7:00 am

Uses

Metronidazole is used for:

All forms of amoebiasis (intestinal and extra-intestinal disease including liver abscess and that of symptomless cyst passers)
Trichomoniasis
Giardiasis
Bacterial vaginosis
Acute ulcerative gingivitis
Anaerobic infections including septicaemia, bacteraemia, peritonitis, brain abscess, necrotising pneumonia, osteomyelitis, puerperal sepsis, pelvic abscess, pelvic cellulitis etc.
Anaerobically-infected leg ulcers and pressure sores
Acute dental infections (e.g. acute pericoronitis and acute apical infections)
Surgical prophylaxis (prevention of postoperative infections due to anaerobic bacteria, particularly species of bacteroides and anaerobic streptococci
Chronic symptomatic peptic ulcer disease (as an agent of triple therapy to eradicate H. pylori-the most important aetiological factor of peptic ulcer)

Tetracycline ointment is used for followings-

Treatment of bacterial conjunctivitis
Treatment of trachoma (by preference use oral azithromycin for this indication)
Prevention of chlamydial and gonococcal neonatal conjunctivitis

Tetracycline is the drug of choice in the following infections :

Ricketsial infection (Rocky Mountain spotted fever, endemic and scrub typhus fever and human ehrlichiosis).
Mycoplasma pneumoniae infections in adults. Outbreaks of pneumonia caused by this organism are common in barracks and institutions. Most cases occur in children and young adults. Maculopapular rashes, haemolytic anaemia and meningo-encephalitis occur rarely.
Chlamydial Infections: Chlamydia psittaci: This organism is the cause of psittacosis (ornithosis), a systemic illness contracted from infected birds. The pneumonia associated with it may be extensive, and severe systemic upset and death are common.Headache is a prominent early symptom.
Non-gonococcal or non specific urethritis: Inflammation of the urethra not resulting from gonococcal, chlamydial, or other specific infectious agents.
Lyme disease
Brucellosis
Miscellaneous infections, including granuloma inguinale, cholera, glanders, relapsing fever and V. vulnifians.

Other common uses of tetracycline include the following:

Urinary Tract Infections with susceptible organisms (including the acute urethral syndrome in women).
Bronchitis in patients with known underlying chronic lung diseases.
Pelvic inflammatory disease and other sexually transmitted diseases (STDs) regimen.
Travelers diarrhoea.
Acne vulgaris
Prostatitis.
As an alternative agent in the penicillin allergic patient with syphilis.
Anaerobic infections with susceptible organisms.

Entakon M is also used to associated treatment for these conditions: Abscess, Intra-Abdominal, Acne Rosacea, Amebiasis, Anaerobic Infection, Bacteremia, Bacterial Endocarditis, Bacterial Peritonitis, Bacterial Vaginosis (BV), Balantidiasis, Bloodstream Infections, Bone and Joint Infections, Brain abscess, CNS Infection, Candidal Vulvovaginitis, Clostridium Difficile Infection (CDI), Empyema, Endometritis, Endomyometritis, Facial Rosacea, Giardiasis, Gynaecological infection, Helicobacter Pylori Infection, Infection, Bacteroides, Intraabdominal Infections, Lower Respiratory Infection, Lower respiratory tract infection bacterial, Lung Abscess, Meningitis, Mixed Vaginal Infections, Parasitic infection NOS, Periodontitis, Pneumonia, Postoperative Infections, Pouchitis, Septicemia bacterial anaerobic, Skin and Subcutaneous Tissue Bacterial Infections, Tetanus, Trichomonal Vaginitis, Trichomonas Vaginitis, Tubo-ovarian abscess, Urethritis, Vulvovaginitis, Asymptomatic Trichomoniasis, Entamoeba histolytica, Hepatic abscess, Refractory Sinusitis, Skin and skin-structure infections, Symptomatic Trichomoniasis, Asymptomatic InfectionsAcinetobacter infection, Acne Rosacea, Actinomycosis, Anthrax, Bacterial Infections, Bartonellosis, Brucellosis, Campylobacter Infection, Chancroid, Chlamydial Infections, Cholera, Conjunctivitis, Inclusion, Cystitis, Endometritis, Entamoebic histolytica infection, Escherichia infections, Gonorrhoea, Granuloma Inguinale, Helicobacter Pylori Infection, Infection, Infection, Bacteroides, Klebsiella Infections, Listeria infection, Lower respiratory tract infection bacterial, Lymphogranuloma Venereum, Necrotizing ulcerative gingivostomatitis, Neisseria Gonorrhoeae Infection, Nephritis, Ornithosis, Plague, Prostatitis, Psittacosis, Q Fever, Relapsing Fever, Rickettsialpox, Rocky Mountain Spotted Fever, Severe Acne, Shigella Infection, Skin and Subcutaneous Tissue Bacterial Infections, Skin infection caused by Staphylococcus aureus, Syphilis, Trachoma, Tularemia, Typhus, Urinary Tract Infection, Yaws, Bacterial upper respiratory tract infections, Clostridia infections, Grade 1, grade 2, grade 3, grade 4 Urinary Tract Infection

How Entakon M works

The exact mechanism of action of metronidazole has not been fully established, however, it is possible that an intermediate in the reduction of metronidazole which is only made by anaerobic bacteria and protozoa, binds deoxyribonucleic acid and electron-transport proteins of organisms, blocking nucleic acid synthesis. After administration, metronidazole enters cells by passive diffusion. Following this, ferredoxin or flavodoxin reduce its nitro group to nitro radicals. The redox potential of the electron transport portions of anaerobic or microaerophilic microorganisms renders metronidazole selective to these organisms, which cause nitro group reduction, leading to the production of toxic metabolites. These include N-(2-hydroxyethyl) oxamic acid and acetamide, which may damage DNA of replicating organisms.

Tetracycline passively diffuses through porin channels in the bacterial membrane and reversibly binds to the 30S ribosomal subunit, preventing binding of tRNA to the mRNA-ribosome complex, and thus interfering with protein synthesis.

Dosage

Entakon M dosage

Tablet and Suspension:

Amoebic dysentery: Duration 5-10 Days;

For Tablet: Adults- 750 mg t.i.d. Children- (7-10 years) 500 mg t.i.d. (3-7 years) 250 mg q.i.d. (1-3 years) 250 mg t.i.d.
For Suspension: Adults- 800 mg t.i.d. Children- (7-10 years) 500 mg t.i.d. (3-7 years) 200 mg q.i.d. (1-3 years) 200 mg t.i.d.

Asymptomatic amoebiasis: Duration 5-10 Days;

For Tablet: Adults- 500-750 mg t.i.d. Children- (7-10 years) 250-500 mg t.i.d. (3-7 years) 250 mg q.i.d. (1-3 years) 250 mg t.i.d.
For Suspension: Adults- 500-800 mg t.i.d. Children- (7-10 years) 200-500 mg t.i.d.; (3-7 years) 200 mg q.i.d.; (1-3 years) 200 mg t.i.d.

Hepatic extraintestinal amoebiasis : Duration 5-10 Days (or 2days);

For Tablet: Adults- 500-750 mg t.i.d.; Children- (7-10 years) 250-500 mg t.i.d.; (3-7 years) 250 mg q.i.d.; (1-3 years) 250 mg t.i.d.
For Suspension: Adults- 500-800 mg t.i.d.; Children- (7-10 years) 200-500 mg t.i.d.; (3-7 years) 200 mg q.i.d.; (1-3 years) 200 mg t.i.d.

Giardiasis: Duration 3 Days;

For Tablet: Adults- 2 g once daily; Children-(7-10 years) 1g once daily; (3-7 years) 750 mg once daily; (1-3 years) 500 mg once daily.
For suspension: Adults- 2 g once daily; Children-(7-10 years) 1g once daily; (3-7 years) 800 mg once daily; (1-3 years) 500 mg once daily.

Trichomoniasis: Duration 7 Days;

For Tablet: Adults- 250 mg t.i.d.; Children- (7-10 years) 100 mg t.i.d.; (3-7 years) 100 mg b.i.d.; (1-3 years) 50 mg t.i.d.
For Suspension: Adults- 200 mg t.i.d.; Children- (7-10 years) 100 mg t.i.d.; (3-7 years) 100 mg b.i.d.; (1-3 years) 50 mg t.i.d.

Trichomoniasis: Duration 1 Day;

For Tablet: Adults- 2 g single dose;
For Suspension: Adults- 2 g single dose;

Vincent's infection (Ulceration of mucous membrane of respiratory tract & mouth): Duration 3 Days;

For Tablet: Adults- 250 mg t.i.d. or 500 mg b.i.d; Children- (7-10 years) 100 mg t.i.d.; (3-7 years) 100 mg b.i.d.; (1-3 years) 50 mg t.i.d.
For Suspension: Adults- 200 mg t.i.d. or 500 mg b.i.d; Children- (7-10 years) 100 mg t.i.d.; (3-7 years) 100 mg b.i.d.; (1-3 years) 50 mg t.i.d.

Periodontal infection: Duration 3 Days;

For Tablet: Adults- 250 mg t.i.d.; Children- (7-10 years) 100 mg t.i.d.; (3-7 years) 100 mg b.i.d.; (1-3 years) 50 mg t.i.d.
For Suspension: Adults- 200 mg t.i.d.; Children- (7-10 years) 100 mg t.i.d.; (3-7 years) 100 mg b.i.d.; (1-3 years) 50 mg t.i.d.

Severe dental infection: Duration 3 Days;

For Tablet: Adults- 500 mg t.i.d.; Children- (7-10 years) 100 mg t.i.d.; (3-7 years) 100 mg b.i.d.; (1-3 years) 50 mg t.i.d.
For Suspension: Adults- 500 mg t.i.d.; Children- (7-10 years) 100 mg t.i.d.; (3-7 years) 100 mg b.i.d.; (1-3 years) 50 mg t.i.d.

Anaerobic infection: Duration 7 Days;

For Tablet: Adults- 500 mg t.i.d.; Children- 7.5 mg/kg body weight t.i.d.
For Suspension: Adults- 500 mg t.i.d.; Children- 7.5 mg/kg body weight t.i.d.

Postoperative anaerobic infection (specially in operation abdominal or gynecological surgery): Duration 7 Days;

For Tablet: Adults- 500 mg t.i.d. before and after operation; Children- 7.5 mg/kg body weight t.i.d.
For Suspension: Adults- 500 mg t.i.d. before and after operation; Children- 7.5 mg/kg body weight t.i.d.

Bacterial vaginitis: Duration 7 Days;

For Tablet: Adults- 500 mg b.i.d.
For Suspension: Adults- 500 mg b.i.d.

Leg ulcers: Duration 1 Day;

For Tablet: Adults- 2 g as a single dose
For Suspension: Adults- 2 g as a single dose

Pressure sores: Duration 7 Days;

For Tablet: Adults- 500 mg t.i.d.
For Suspension: Adults- 500 mg t.i.d.

H. pylori infection: Duration 7 Days;

For Tablet: Adults- 500 mg b.i.d
For Suspension: Adults-500 mg b.i.d

Antibiotic Associated Pseudomembranus colitis: Duration 7 Days;

For Tablet: Adults- 500 mg b.i.d
For Suspension: Adults- 500 mg b.i.d

Vaginal Gel:

The recommended dose is one applicator full of Metronidazole GEL (approximately 5 grams containing approximately 37.5 mg of Metronidazole) intravaginally once or twice a day for 5 days. For once a day dosing, Metronidazole GEL should be administered at bedtime.

Suppository:

Anaerobic infections:

Adult: 1 g 8 hrly for 3 days, then 12 hrly thereafter until oral medication is possible.
Child: 5-10 yr 500 mg. All doses to be given 8 hrly for 3 days, then 12 hrly thereafter until oral medication is possible.

Prophylaxis of postoperative anaerobic bacterial infections:

Adult: 1 g 2 hr before surgery, repeated 8 hrly for 3 days, then 12 hrly thereafter until oral medication is possible.
Child: 5-10 yr 500 mg 2 hr before surgery, repeated 8 hrly for 3 days, then 12 hrly thereafter until oral medication is possible.

IV Infusion:

Metronidazole injection should be infused intravenously at an approximate rate of 5 ml/min. Oral medication should be substituted as soon as feasible. Treatment for 7 days should be satisfactory for most patients, but the physician might decide to prolong treatment.

For bacterial infections: Adults: 500 mg (100 ml) 8 hourly. Children: 7.5 mg/kg (1.5 ml/kg) 8 hourly.
For treatment before and during surgery: Adults: 500 mg (100 ml) shortly before operation, repeated 8 hourly. Children: 7.5 mg/kg (1.5 ml/kg) 8 hourly

The usual adult oral dosage of Tetracycline is 1-2 g daily given in 2-4 divided doses. The usual oral dosage of Tetracycline for children older than 8 years of age in 25-50 mg/kg daily given in 2-4 divided doses. Alternatively some clinicians recommended that children should receive 0.6-1.2 g/m2 daily.

Tetracycline should be taken preferably one hour before or 2 hours after meals.

Some specific indications along with some information on dosage is given below:

Acne vulgaris: 250 mg four times daily or 500 mg 12 hourly for 1 week; 125-250 mg for several weeks or months.Duration of therapy is determined by individual progress

Acutestaphylococcal infections: 1-2 g daily in divideddoses for 10-14 days

Acute streptococcal infections:1-2 g daily in divided doses for 10 days.Prolonged therapy is needed to avoid risk of rheumatic fever or glomerulonephritis

Amoebiasis:1 g daily in four divided doses or 500 mg 12 hourly for 7 days.Given in association with amoebicidal agents

Brucellosis: 500 mg four times daily plus 1 g streptomycin twice daily for 1 week ; then 500 mg four times daily (no streptomycin) for 1 week.Prolonged therapy is necessary to avoid relapse

Subacute bacterial endocarditis:1-2 g daily in divided doses for 6 weeks.Usually given in combination with a bactericidal agent

Syphilis:Total 30-40 g given in divided doses over 10-15 days.Serology and spinal fluid examination should follow the administration of tetracycline

Wash the eyes with boiled and cooled water before each application. Use sterile sodium chloride 0.9% for newborns. Apply tetracycline 1% into the conjunctival sac of both eyes:

Conjunctivitis: one application 2 times daily for 7 days
Trachoma: one application 2 times dailyfor 6 weeks
Prevention of neonatal conjunctivitis: one single application immediately after birth

Side Effects

Side effects of Metronidazole include gastrointestinal discomfort, nausea, coated tongue, dryness of mouth and unpleasant metallic or bitter taste, headache, pruritus and skin rashes and less frequently, vertigo, depression, insomnia, drowsiness, urethral discomfort, and darkening of the urine. Occasionally there may be temporary moderate leucopenia. Peripheral neuropathy has been reported in patients on prolonged therapy.

Teeth and bone: Tetracycline can cause depression of bone growth, permanent graybrown discoloration of the teeth and enamel hypoplasia when given during tooth development (i.e. during the later half of pregnancy, during infancy and in childhood).

Hypersensitivity reactions such as anaphylaxis, urticaria and rashes are uncommon. Photosensitivity reactions consisting of a red rash on areas exposed to intense sunlight can occur with Tetracycline.

Gastrointestinal effects: Epigastric distress and nausea are commonly seen after oral administration, and these symptoms are somewhat dose related. Vomiting can occur.

Accentuated prerenal azotemia: Tetracycline appears to aggravate pre-existing renal failure by inhibiting protein synthesis, which increases the azotemia from amino acid metabolism.

Superinfections with oral and anogenital candidiasis are relatively common in patients taking Tetracycline.

Esophageal ulcerations: In most cases, the patients were taking the capsules with little or no fluid before going to bed. To help minimize this, oral doses should be given with adequate amounts of fluid.

Eye/Ear: Burning, irritation, visual disturbances, superinfections, photosensitivity, hypersensitivity

Toxicity

LD50 information

The oral LD50 of metronidazole in rats is 5000 mg/kg

Overdose information

Adverse effects that may be exaggerated with an overdose include peripheral neuropathy, central nervous system toxicity, seizures, disulfiram-like effect (if combined with alcohol) dark urine, a metallic taste in the mouth, nausea, epigastric discomfort, and vertigo, in addition to neutropenia. There is no specific antidote for metronidazole overdose. Symptomatic and supportive treatment should be employed in addition to the administration of activated charcoal to remove the unabsorbed drug from the gastrointestinal tract. In addition to the above measures, contact the local poison control center for updated information on the management of a metronidazole overdose.

LD₅₀=808mg/kg (orally in mice)

Precaution

Metronidazole should not be used in patients with blood dyscrasia. It is suggested that it should not be given in the first three months of pregnancy. When given in conjunction with alcohol, Metronidazole may provoke a disulphiram like effect.

Care should be taken if Tetracycline Hydrochloride is given to patients with impaired liver function and high doses should be avoided. Potentiality hepatotoxic drugs (including erythromycin, chloramphenicol, isoniazide and sulphonamides) should not be given concomitantly.

Hepatic impairment. Avoid exposure to sunlight. Periodic evaluation of renal, hepatic and haematological system during prolonged therapy.

Interaction

Metronidazole interacts with warfarin, nicoumalone, phenytoin, phenobarbitone, fluorouracil, disulfiram, lithium, cimetidine etc.

Impaired absorption with antacids containing divalent and trivalent cations (e.g. Al, Ca, Mg), Fe, Zn and Na bicarbonate preparations, kaolin-pectin, bismuth subsalicylate, sucralfate, strontium ranelate, colestipol and colestyramine. May interfere with the bactericidal action of penicillin. May potentiate the effect of anticoagulants. May decrease efficacy of oral contraceptives. Nephrotoxic effects may be exacerbated by diuretics or other nephrotoxic drugs. May increase the hypoglycaemic effect of insulin and sulfonylureas in patients with DM. May increase toxic effects of ergot alkaloids and methotrexate.

Volume of Distribution

Metronidazole is widely distributed throughout the body and various body fluids. They include the bile, saliva, breastmilk, cerebrospinal fluid, and the placenta. Steady-state volume distribution of metronidazole in adults ranges from 0.51 to 1.1 L/kg. It attains 60 to 100% of plasma concentrations in various tissues, such as the central nervous system, however, is not measured in high concentrations in the placental tissue.

Elimination Route

After the intravenous infusion of a 1.5g dose, peak concentration was reached within 1 hour and was peak level of 30-40 mg/L. When a multiple-dose regimen of 500mg three times a day administered intravenously, steady-state concentrations were achieved within about 3 days and peak concentration was measured at 26 mg/L. When administered orally in the tablet form, metronidazole is absorbed entirely absorbed, showing a bioavailability of greater than 90%. One resource indicates that Cmax after a single oral dose of 500mg metronidazole ranges from 8 to 13 mg/L, with a Tmax of 25 minutes to 4 hours. The AUC following a single 500mg oral dose of metronidazole was 122 ± 10.3 mg/L • h.

A note on the absorption of topical preparations

Insignificant percutaneous absorption of metronidazole occurs after the application of 1% metronidazole cream topically. Healthy volunteers applied one 100 mg dose of 14C-labelled metronidazole 2% cream to unbroken skin. After 12 hours, metronidazole was not detected in the plasma. Approximately 0.1% to 1% of the administered metronidazole was measured in the urine and feces.

Bioavailability is less than 40% when administered via intramuscular injection, 100% intravenously, and 60-80% orally (fasting adults). Food and/or milk reduce GI absorption of oral preparations of tetracycline by 50% or more.

Half Life

The elimination half-life of metronidazole is 7.3 ± 1.0 after a single 500mg IV dose in healthy subjects. Another resource indicates that the elimination half-life for metronidazole ranges from 6 to 10 hours.

6-12 hours

Clearance

Dose adjustments may be required in patients with hepatic impairment, as clearance is impaired in these patients. The clearance of metronidazole in the kidneys is estimated at 10 mL/min/1.73 m2. The total clearance from serum is about 2.1 to 6.4 L/h/kg.

Elimination Route

Metronidazole and metabolites are 60 to 80% eliminated in the urine, and 6-15% excreted in the feces.

They are concentrated by the liver in the bile and excreted in the urine and feces at high concentrations in a biologically active form.

Pregnancy & Breastfeeding use

Not recommended during first & later trimesters. Breast feeding should be delayed until 48 hours after discontinuing metronidazole in the mother.

Tetracycline should not be used during pregnancy because of the risk of hypertoxicity in the mother as well as the effects on the developing foetus. Use in pregnancy potentially during breast-feeding and in children up to the age of 8, or some authorise say 12 years, may result in impaired bone growth and permanent discoloration of the child's teeth.

Contraindication

Metronidazole is contraindicated in patients with prior history of hypersensitivity to Metronidazole or other Nitroimidazole derivatives.

Tetracycline Hydrochloride is contraindicated in patients hypersensitive to any of the member of tetracycline groups, since cross-sensitivity may occur Tetracycline Hydrochloride should be avoided in patients with systemic lupus erythematosus. Tetracycline Hydrochloride is considered to be contraindicated in renal impairment, particularly if severe ; if it must be given, doses should be reduced.